Electron spin wave filter, demultiplexer, and filtering method

Abstract

An electron spin wave filter 1 comprises: a one-dimensional thin wire structure 10 through which electron spin waves propagate; a gate electrode 11 which is located along a part of the one-dimensional thin wire structure 10; a first ohmic electrode 12 which is disposed upstream from the gate electrode 11 and is in ohmic contact with the one-dimensional thin wire structure 10; and a second ohmic electrode 13 which is disposed downstream from the gate electrode 11 and is in ohmic contact with the one-dimensional thin wire structure 10. When receiving input of electron spin waves having a plurality of wavelengths included in a first wavelength range, the electron spin wave filter 1 outputs only electron spin waves having wavelengths included in the first wavelength range and included in a second wavelength range narrower than the first wavelength range.

Description

Electron spin wave filter, demultiplexer and filtering method

[0001] The present invention relates to an electron spin wave filter that selectively passes electron spin waves having a specific wavelength from electron spin waves having multiple wavelengths. The present invention also relates to a demultiplexer using such an electron spin wave filter and a method for filtering electron spin waves using such an electron spin wave filter.

[0002] Electron spin waves are a phenomenon in which electron spins propagate through space while changing their direction, and as a wave they possess both "parallelism" and "multiplicity." Therefore, in principle, it is possible to transmit electron spin waves that are the superposition of electron spin waves with different wavelengths (also called "multiple electron spin waves") and separate the wavelengths for use.

[0003] Electron spin waves can be generated by the effective magnetic field created by spin-orbit interaction (SOI) within a semiconductor, either by spin generation through irradiation of a semiconductor with polarized light or by spin injection from a ferromagnet into the semiconductor. For example, in III-V semiconductor quantum well structures, there are two types of SOI: Rashba SOI and Dresselhaus SOI. When the absolute values ​​of the effective magnetic fields created by these two SOIs are equal (where the magnitude of the Rashba SOI is represented by coefficient α and the magnitude of the Dresselhaus SOI is represented by coefficient β, this means |α| = |β|), spin relaxation is suppressed, allowing electron spin waves to exist stably. This state is called a persistent spin gyration (PSH) state.

[0004] Here, the magnitude (β) of the Dresselhaus SOI is a specific value determined by the material, while the magnitude (α) of the Rashba spin-orbit interaction varies depending on the carrier concentration. The carrier concentration can be controlled by the amount of impurity doped into the quantum well structure, or it can be continuously varied by providing a gate electrode outside the quantum well structure and applying a voltage to the gate electrode (see, for example, Non-Patent Document 1).

[0005] In Patent Document 1, wavelength λ １ = 20 μm, λ ２ = 6.7 μm, λ ３= 3.3 μm propagating in the X direction, a multiple electron spin wave is generated by superposing three electron spin waves, and the wavelength is λ ２ The electron spin wave of the wavelength λ is incident on a two-dimensional planar quantum well structure in the PSH state, and after 1 ns, it is drift-transported by applying a voltage in the +Y direction. １ and wavelength λ ３ The electron spin wave of wavelength λ ２ This shows that only electron spin waves of wavelengths that produce PSH states survive. In other words, it has been proposed to use a semiconductor quantum well structure with a gate electrode as a filter by taking advantage of the fact that electron spin waves of wavelengths that produce PSH states have a longer lifetime and are more stable than electron spin waves of other wavelengths. It has also been described that in this filter, the wavelengths that pass can be controlled by the gate voltage applied.

[0006] In addition, Non-Patent Document 2 states that when three electron spin waves with different wavelengths are excited in a quantum well with a one-dimensional wire structure at t=0 (ns), the wave number q ０ but It is stated that only waves equal to m are maintained, and waves with different wave numbers are lost. ＊ is the effective mass of the electron, is the reduced Planck constant. Based on this finding, it is reported that it is possible to filter electron spin waves by modulating the size of the Rashba SOI through gate voltage control.

[0007] International Publication No. 2023 / 203665

[0008] “Gate-controlled switching between persistent and inverse persistent spin helix states”, K. Yoshizumi, A. Sasaki, M. Kohda and J. Nitta, APPLIED PHYSICS LETTERS 108, 132402 (2016) “Proposal of electron spin wave filter in semiconductor two-dimensional electron gas”, K. Kikuchi, N. Nakajima, S. Karubé, C. Zhang, and M. Kohda, Proceedings of the 70th Spring Meeting of the Japan Society of Applied Physics, 2023, 16p-D704-2

[0009] It is conceivable that by using electron spin waves, wavelength division multiplexing (WDM) can be performed in a solid-state device, and after separating the electron spin waves with the above-mentioned filter, logical operations and the like can be performed in parallel processing. For this purpose, in filtering, it is necessary to transport the electron spin waves from a preceding device to a filter, separate them, and then transport them to a succeeding device.

[0010] Patent Document 1 specifically discloses a two-dimensional filter that drift-transports electron spin waves propagating in the X direction in the Y direction, but two-dimensional filters require a large footprint and are therefore not suitable for miniaturization. Furthermore, it is easier to control the wavelength and other properties of electron spin waves in the PSH state by confining them in a thin, narrow one-dimensional wire structure than by confining them in a thin, two-dimensional planar structure. Therefore, a one-dimensional filter that drift-transports electron spin waves propagating in the X direction in the X direction and passes them on to a downstream device is preferred, but it is known that the wavelength of the electron spin wave changes depending on the electron drift velocity (see paragraph

[0028] of Patent Document 1).

[0011] The present invention has been made in consideration of these problems, and its purpose is to provide a filtering method for a one-dimensional electron spin wave filter that is not affected by wavelength changes due to drift, and an electron spin wave filter that can realize this filtering method.

[0012] In order to solve the above problems, an electron spin wave filter according to one embodiment of the present invention comprises: a one-dimensional thin-wire structure through which electron spin waves propagate; a gate electrode along part of the one-dimensional thin-wire structure; a first ohmic electrode arranged upstream of the gate electrode and making ohmic contact with the one-dimensional thin-wire structure; and a second ohmic electrode arranged downstream of the gate electrode and making ohmic contact with the one-dimensional thin-wire structure. When electron spin waves having multiple wavelengths included in a first wavelength range are input to this electron spin wave filter, the filter outputs only electron spin waves having wavelengths included in the first wavelength range but in a second wavelength range narrower than the first wavelength range.

[0013] An electron spin wave filter according to one embodiment may include a third ohmic electrode disposed between the first ohmic electrode and the gate electrode and in ohmic contact with the one-dimensional thin-wire structure, a fourth ohmic electrode disposed between the gate electrode and the second ohmic electrode and in ohmic contact with the one-dimensional thin-wire structure, and a switching element that switches the connection between the third ohmic electrode and the fourth ohmic electrode between an on state and an off state.

[0014] In some embodiments, the one-dimensional wire structure may be a semiconductor quantum well.

[0015] In one embodiment, the spin diffusion coefficient of the one-dimensional wire structure at a temperature of 15 K is 0.02 m ２ / s or more.

[0016] In an embodiment, the length of the gate electrode along the one-dimensional wire structure may be 200 μm or less.

[0017] Another aspect of the present invention is a demultiplexer in which a one-dimensional thin-wire structure is branched into multiple branches, each branch having the above-mentioned electron spin wave filter. When electron spin waves having multiple wavelengths included in a first wavelength range are input to this demultiplexer, only electron spin waves having wavelengths included in the first wavelength range but included in a second wavelength range narrower than the first wavelength range are output from a first electron spin wave filter located at an arbitrarily selected first branch, and only electron spin waves included in a third wavelength range included in the first wavelength range but narrower than the first wavelength range are output from a second electron spin wave filter located at an arbitrarily selected second branch. The second wavelength range and the third wavelength range do not overlap.

[0018] Yet another aspect of the present invention is a method for filtering electron spin waves using the above-described electron spin wave filter, comprising the steps of applying a voltage between a first ohmic electrode and a second ohmic electrode, injecting electron spin waves having multiple wavelengths within a first wavelength range into a first portion of the one-dimensional wire structure located between the first ohmic electrode and a gate electrode, or irradiating the first portion with polarized light to generate electron spin waves having multiple wavelengths within the first wavelength range, drifting the electron spin waves along the one-dimensional wire structure, and outputting only electron spin waves having wavelengths within a second wavelength range from a second portion of the one-dimensional wire structure located between the gate electrode and the second ohmic electrode.

[0019] A method for filtering electron spin waves in one embodiment may include the steps of applying a voltage between a first ohmic electrode and a second ohmic electrode, irradiating polarized light onto a third portion along a gate electrode of the one-dimensional wire structure to generate electron spin waves having multiple wavelengths included in a first wavelength range, drifting and transporting the electron spin waves along the one-dimensional wire structure, and outputting only electron spin waves having wavelengths included in a second wavelength range from a second portion located between the gate electrode of the one-dimensional wire structure and the second ohmic electrode.

[0020] a step of applying a voltage between a first ohmic electrode and a second ohmic electrode; a step of turning off a switching element; a step of injecting electron spin waves having a plurality of wavelengths included in a first wavelength range into a fourth portion located between the first ohmic electrode and a third ohmic electrode of the one-dimensional thin-wire structure, or a step of irradiating the fourth portion with polarized light to generate electron spin waves having a plurality of wavelengths included in the first wavelength range; a step of drift-transporting the electron spin waves through the one-dimensional thin-wire structure; a step of turning on the switching element to diffuse-transport the electron spin waves; a step of turning off the switching element after a predetermined time has elapsed to drift-transport the electron spin waves; and a step of outputting only electron spin waves having a wavelength included in the second wavelength range from a fifth portion located between the fourth ohmic electrode and the second ohmic electrode of the one-dimensional thin-wire structure.

[0021] A method for filtering electron spin waves in one embodiment may include the steps of applying a voltage between the first ohmic electrode and the second ohmic electrode, irradiating a sixth portion along the gate electrode with polarized light to generate electron spin waves having a plurality of wavelengths included in a first wavelength range, turning on a switching element to diffuse and transport the electron spin waves, turning off the switching element after a predetermined time has elapsed to drift and transport the electron spin waves, and outputting only electron spin waves having wavelengths included in the second wavelength range from a fifth portion located between the fourth ohmic electrode and the second ohmic electrode of the one-dimensional thin wire structure.

[0022] In one embodiment, the spin diffusion coefficient of the one-dimensional wire structure at the filtering operating temperature is 0.02 m ２ / s or more, and the predetermined time may be 0.1 ns or more and 1 μs or less.

[0023] In one embodiment, the spin diffusion coefficient of the one-dimensional wire structure is 0.05 m ２ / s or more, and the predetermined time may be 0.1 ns or more and 0.1 μs or less.

[0024] Any combination of the above components, and conversion of the present disclosure into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present disclosure.

[0025] According to the present invention, a one-dimensional electron spin wave filtering method that is not affected by wavelength changes due to drift is realized, and an electron spin wave filter that can realize this filtering method can be implemented as a solid-state device that can be connected to a previous and subsequent stage.

[0026] Fig. 1 is a schematic cross-sectional view of an electron spin wave filter according to a first embodiment; Fig. 2 is a schematic cross-sectional view of an electron spin wave filter according to a second embodiment; Fig. 3 is a schematic view of a demultiplexer according to a third embodiment; Fig. 4 is a diagram showing the results of a simulation of a waveform after multiple electron spin waves have been held for 1 ns in a one-dimensional thin-wire structure of a GaAs / AlGaAs quantum well; Fig. 5 is a diagram showing the results of a simulation of a waveform after multiple electron spin waves have been held for 1 ns in a one-dimensional thin-wire structure of a GaAs / AlGaAs quantum well.

[0027] The present invention will be described below based on preferred embodiments with reference to the drawings. The embodiments are illustrative and do not limit the invention. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention. Identical or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant description will be omitted where appropriate. Furthermore, the scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and should not be interpreted as limiting unless otherwise specified. When terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not indicate any order or importance, but are intended only to distinguish one configuration from another. Furthermore, in each drawing, some components that are not important for explaining the embodiments are omitted.

[0028] [One-dimensional wire structure] A quantum well with a two-dimensional planar structure can be obtained by confining electrons in a well-shaped potential in the z direction and restricting the degrees of freedom to the xy plane. Furthermore, a well-shaped potential in the y direction can be added to restrict the degrees of freedom to only the x direction, resulting in a quantum well with a one-dimensional wire structure. Quantum effects can be expressed by confining electrons in a quantum well.

[0029] As one embodiment, an InGaAs / InAlAs quantum well will be described. Such a quantum well can be constructed with the following layered structure (see, for example, Non-Patent Document 1). Specifically, in the example of Non-Patent Document 1, a one-dimensional thin-wire structure extending in the [1 1 0] direction is fabricated by epitaxially growing an InGaAs quantum well on an InP (001) substrate using metal organic chemical vapor deposition (MOCVD). The films are stacked in the z direction in the following order from the InP substrate: 200 nm In ０．５２ Al ０．４８ As 6nm In ０．５２ Al ０．４８ As (1.2 × 10 １８ cm －３ Si doping) 6 nm In ０．５２ Al ０．４８ As 7nm In ０．５３ Ga ０．４７ As quantum well 6nm In ０．５２ Al ０．４８ As 6nm In ０．５２ Al ０．４８ As (3.2 × 10 １８ cm －３ Si doping) 10 nm In ０．５２ Al ０．４８ As where the gate insulating layer (5 nm Al ２ O ３ / 95nm HfO ２ ), and a gate electrode (10 nm Cr / 100 nm Au) is used.

[0030] Alternatively, a GaAs / AlGaAs quantum well is described. The films are deposited in the z direction starting from a GaAs (001) substrate as follows: 200 nm GaAs, 18 nm Al. ０．３ Ga０．７ As 2nm GaAs 100nm Al ０．３ Ga ０．７ As 20nm GaAs quantum well 35nm Al ０．３ Ga ０．７ As 20m Al ０．３ Ga ０．７ As (6 x 10 １８ cm －３ (Si doped) 5nm GaAs

[0031] 1 is a cross-sectional schematic diagram of an electron spin wave filter 1 according to a first embodiment. The electron spin wave filter 1 comprises a one-dimensional wire structure 10 through which electron spin waves propagate, a gate electrode 11 along part of the one-dimensional wire structure 10, a first ohmic electrode 12 arranged upstream of the gate electrode 11, and a second ohmic electrode 13 arranged downstream of the gate electrode 11.

[0032] The one-dimensional wire structure 10 comprises an input section 20 that generates electron spin waves by irradiation with polarized light or by spin injection from a ferromagnetic layer joined to the one-dimensional wire structure 10, or that receives as input electron spin waves output from another adjacent one-dimensional wire structure, and an output section 21 that outputs electron spin waves that have propagated through the one-dimensional wire structure.

[0033] The input section 20 is arranged on the one-dimensional wire structure 10 in a portion between the gate electrode 11 and the first ohmic electrode 12 (hereinafter, in the first embodiment, also referred to as the "first portion"), or is arranged on the one-dimensional wire structure 10 along the gate electrode 11.

[0034] The output section 21 is disposed in a portion of the one-dimensional thin-wire structure 10 between the gate electrode 11 and the second ohmic electrode 13 (hereinafter, also referred to as the "second portion" in the first embodiment).

[0035] In the electron spin wave filter 1, by applying a voltage between the first ohmic electrode 12 and the second ohmic electrode 13, electron spin waves in the input section 20 are drift-transported to a section along the gate electrode 11 of the one-dimensional thin-wire structure 1 (hereinafter also referred to as the "gate region", and in the first embodiment also referred to as the "third section"), and then drift-transported from the gate region to the output section 21. As will be described later, the gate length L is set to a value corresponding to the drift velocity v ｄｒｉｆｔ By making the length of the time longer than the product of the time and the response time (time for filtering) t, filtering can be performed simultaneously with drift transport through the gate region.

[0036] 2 is a cross-sectional view of an electron spin wave filter 2 according to a second embodiment. The electron spin wave filter 2 includes a one-dimensional wire structure 10 through which electron spin waves propagate, a gate electrode 11 extending along a portion of the one-dimensional wire structure 10, a first ohmic electrode 12 disposed upstream of the gate electrode 11, a second ohmic electrode 13 disposed downstream of the gate electrode 11, a third ohmic electrode 14 disposed between the gate electrode 11 and the first ohmic electrode 12, a fourth ohmic electrode 15 disposed between the gate electrode 11 and the second ohmic electrode, and a switching element 16 for short-circuiting the third ohmic electrode 14 and the fourth ohmic electrode 15 to achieve an equipotential. In other words, the electron spin wave filter 2 includes the third ohmic electrode 14, the fourth ohmic electrode 15, and the switching element 16 in addition to the configuration of the electron spin wave filter 1 shown in FIG. 1 . The other configurations of the electron spin wave filter 2 are the same as those of the electron spin wave filter 1 .

[0037] As in the electron spin wave filter 1, in the electron spin wave filter 2, by applying a voltage between the first ohmic electrode and the second ohmic electrode, electron spin waves in the input section (hereinafter also referred to as the "fourth section" in the second embodiment) are drift-transported to the gate region (hereinafter also referred to as the "sixth section" in the second embodiment), and then drift-transported from the gate region to the output section (hereinafter also referred to as the "fifth section" in the second embodiment).

[0038] A unique function of the electron spin wave filter 2 is that, for a response time t after the electron spin wave is transported to the gate region, the third ohmic electrode 14 and the fourth ohmic electrode 15 are short-circuited to make them equipotential, thereby stopping drift transport and allowing only diffusion transport. ｄｒｉｆｔ Even when the wavelength of the electron spin wave changes quickly or when the gate length cannot be increased, it is possible to stop drift transport in the gate region and perform filtering by diffusion transport. Cases where such a function is required will be discussed later.

[0039] [Third embodiment: Demultiplexer] A one-dimensional thin-wire structure is branched into multiple parts at the end of the input section, and an electron spin wave filter of the first or second embodiment is formed on each of the multiple branched one-dimensional thin-wire structures. By changing the pass frequency band of each, a demultiplexer that wavelength-divides multiple electron spin waves can be constructed.

[0040] 3 is a schematic diagram of a demultiplexer 3 according to a third embodiment. The demultiplexer 3 includes a one-dimensional wire structure 30, a first electron spin wave filter 41, a second electron spin wave filter 42, and a third electron spin wave filter 43.

[0041] The one-dimensional wire structure 30 has an input section 31 to which electron spin waves are input. The one-dimensional wire structure 30 branches into three at the tip of the input section 31. A first electron spin wave filter 41, a second electron spin wave filter 42, and a third electron spin wave filter 43 are formed at the tips of the branches of the one-dimensional wire structure 30, respectively.

[0042] The first electron spin wave filter 41 includes a gate electrode 411 and an output section 412. The second electron spin wave filter 42 includes a gate electrode 421 and an output section 422. The third electron spin wave filter 43 includes a gate electrode 431 and an output section 432. Although not shown in FIG. 3 , a first ohmic electrode is provided on the upstream side (the input section 31 side) of each of the gate electrodes 411, 421, and 431. Furthermore, a second ohmic electrode is provided on the downstream side (the output section 412, 422, and 432 side) of each of the gate electrodes 411, 421, and 431.

[0043] When an electron spin wave is input, the first electron spin wave filter 41 converts the electron spin wave into a wave with a wavelength λ １ When an electron spin wave is input to the second electron spin wave filter 42, only the electron spin wave in the first wavelength range including the wavelength λ is output from the output section 412. ２ When the electron spin wave is input, the third electron spin wave filter 43 outputs only the electron spin wave in the second wavelength range including the wavelength λ ３ Only electron spin waves in the third wavelength range including the wavelengths .lamda. and .lamda. are output from the output section 413. However, it is assumed that there is no overlapping portion among the first, second, and third wavelength ranges.

[0044] Demultiplexer 3 receives a signal of wavelength λ １ , λ ２ and λ ３ When an electron spin wave having a wavelength λ １ and the output section 422 outputs only electron spin waves in a first wavelength range including the wavelength λ ２ and the output section 432 outputs only electron spin waves in the second wavelength range including the wavelength λ ３ Only electron spin waves in the third wavelength range including

[0045] In the above example, the number of branches in the one-dimensional thin wire structure is set to three, but the number of branches is not limited to this. That is, the number of branches in the one-dimensional thin wire structure may be two, or any number equal to or greater than four.

[0046] In this way, according to this embodiment, a demultiplexer that divides multiple electron spin waves into wavelengths can be realized.

[0047] Simulations performed to verify the operation and effectiveness of the present disclosure are described below. [Passing Center Wave Number and Bandwidth of Electron Spin Wave Filter] Parameters that affect frequency separation performance in an electron spin wave filter were simulated.

[0048] The central wave number q of the electron spin wave in the PSH state passing through the filter ０ is expressed by the following formula: α is the Rashba SOI coefficient, β is the Dresselhaus SOI coefficient, m ＊ is the effective mass of the electron, is the reduced Planck constant. That is, the central wave number q ０ is determined by the SOI coefficients α and β of the material. Note that the sign of β can be either positive or negative depending on the definition of the direction of the electric field of the crystal field, but in this specification it is assumed to be positive.

[0049] The central wave number q at which the wave number becomes a PSH state ０ Off the mark q ｘ When this happens, the relaxation rate of the electron spin wave is 1 / τ ｓ (τ ｓ is the relaxation time) is expressed by the following quadratic formula: ｓ is the spin diffusion constant determined by the filtering operating temperature and the material of the quantum well structure, τ ＰＳＨ is the relaxation time in the PSH state. ｓ =D ｓ (q ｘ -q ０ ) ２ +1 / τ ＰＳＨ

[0050] τ ＰＳＨ is sufficiently long, 1 / τ ＰＳＨ is approximately 0, and the relaxation rate is ０ The width Δq of the wavenumbers that are within -3 dB of the value ｘ (hereinafter also referred to as "bandwidth") is calculated as follows: Δq ｘ = 2(-ln(1 / 2 ０．５ ) / (D ｓ ×t)) ０．５where t is the response time. That is, the bandwidth is determined by the spin diffusion constant D ｓ and the response time t.

[0051] Therefore, the residence time (response time) t in the gate region required for filtering and the gate length L required for filtering are expressed by the following formula: t = 2ln(2) / (D ｓ × (Δq ｘ ) ２ ) L = (2D ｓ ×t) ０．５ = 2(ln(2)) ０．５ / Δq ｘ

[0052] [Simulation] Specifically, a simulation was performed on the waveform after multiple electron spin waves were held for 1 ns in a one-dimensional thin wire structure of GaAs / AlGaAs quantum wells with a width of 1 μm and a length in the x direction of 100 μm. １ =6.5 [μm] (wave number q ｘ =0.96[1 / μm]), wavelength λ ２ = 10.5 [μm] (wave number q ｘ =0.60[1 / μm]), wavelength λ ３ = 17.5 [μm] (wave number q ｘ = 0.36 [1 / μm]). The SOI coefficient is α = -1.70 × 10 －１３ eV m, β = β １ (Linear term) + β ３ (Cubic term), and β １ = 1.70 x 10 －１３ eV m, β ３ = 0 eV m, and the density of two-dimensional electrons is n ｓ = 0.1 × 10 １５ m ―２ is.

[0053] FIG. 4 shows the applied gate voltage with wavelength λ ２ is fixed at a voltage such that PSH is obtained, and the spin diffusion constant D ｓ After a filtering time of 1 ns, D ｓ =0.01m ２In the case of / s, the wavelength separation is insufficient, but D ｓ =0.10m ２ / s or more, the wavelength separation was sufficient. ｓ From the viewpoint of frequency separation performance, ２ / s or more is preferable, and 0.05 m ２ / s or more is more preferable, and 0.10 m ２ / s or more is most preferable. ｓ is 0.02m ２ / s or more, the response time t is preferably 0.1 ns or more and 1 μs or less. ｓ is 0.05m ２ / s or more, the response time t is preferably 0.1 ns or more and 0.1 μs or less.

[0054] FIG. 5 shows the spin diffusion constant D ｓ to 0.10 m ２ 10 is a graph showing the results when the absolute value of the SOI coefficient is changed while the wavelength λ is fixed at 1 / s and the PSH is maintained (|α|=|β|). １ , wavelength λ ２ , wavelength λ ３ As mentioned above, if the one-dimensional wire structure is branched into three branches and these three filters are connected one by one, it will function as a demultiplexer.

[0055] In the one-dimensional wire structure consisting of the above GaAs quantum well, at a filtering operation temperature of 15 K, ｓ =0.10m ２ / s, and Δq ｘ When t=0.3 [1 / μm], the response time t was 0.154 ns and the gate length L was 5.55 μm.

[0056] Next, the spin diffusion constant D ｓ As a material with small wavelength, λ, of the electron spin wave is considered. ＳｎＳ is 1.5 x 10 ２ nm, and the wavelength λ of the electron spin wave in GaAs ＧａＡｓ = 10.5 x 10 ３The spin diffusion constant of SnS is unknown, but since the spin diffusion constant of known materials is about 1 / 10 of the electron diffusion constant, if we assume that the spin diffusion constant of SnS is also 1 / 10 of the electron diffusion constant, then at a filtering operating temperature of 10 K, D ｓ = 4 x 10 －６ m ２ / s. When the filtering operation temperature is room temperature, the spin diffusion constant is further reduced to about 1 / 10. Δq in the case of GaAs ｘ = 0.3 [1 / μm], and for SnS, Δq ｘ = 0.3 × λ ＧａＡｓ / λ ＳｎＳ = 0.3 × 10 ２ When set to [1 / μm], the response time t is 0.385 ns and the gate length L is 39.2 nm. That is, although the response time is somewhat long, a short gate length is sufficient because the diffusion transport is slow.

[0057] As described above, the material constituting the one-dimensional thin wire structure can be selected from materials having an appropriate spin diffusion rate and wavelength, taking into consideration the operating speed and gate length. Furthermore, as described above, it has been found that the gate length can also be made shorter than the value (300 μm) described in Patent Document 1. The upper limit of the gate length is, for example, preferably 200 μm or less, more preferably 50 μm or less, and most preferably 10 μm or less. Setting the gate length to be as short as possible and equal to or greater than L in this way not only makes it suitable for miniaturization, but also enables electron spin waves to be filtered in a short time, thereby suppressing signal attenuation.

[0058] [Effect of Drift Transport on Wavelength] When a filter is connected to a device in the preceding or succeeding stage, drift transport due to an electric field is required. The diffusion rate v ｄｉｆｆ is 10 ３ ~10 ４ m / s order, drift velocity v ｄｒｉｆｔ is 10 at the fastest ５ The drift velocity is usually larger than the diffusion velocity, but the diffusion velocity is 2D ｓ / L, the diffusion velocity may be greater than the drift velocity in special cases, such as when L is short.

[0059] Here, consider the case where drift transport is performed from a device at a previous stage to a filter, and after filtering by the filter, drift transport is performed to a device at a subsequent stage. The aforementioned Patent Document 1 describes that filtered electron spin waves can be obtained by diffusively transporting in the X direction and simultaneously drifting in the Y direction. However, there is no specific description as to whether filtering is possible while drifting in the X direction. As a result of investigation, it is considered that filtering is possible while drift transport is performed if the influence of drift transport on the wavelength of the electron spin wave is small, and in this case, the electron spin wave filter of the first or second embodiment can be used. On the other hand, if the wavelength of the electron spin wave changes due to drift transport, it is necessary to stop drift transport during filtering. In this case, only the electron spin wave filter of the second embodiment can be used. Note that even if the drift velocity increases by increasing the applied voltage and the wavelength of the electron spin wave changes, the drift velocity becomes 0 when the applied voltage is set to 0, and the original wavelength is restored, making filtering by diffusive transport only possible.

[0060] The wavelength of the electron spin wave during drift transport is given by: α: Rashba SOI coefficient, β: Dresselhaus SOI coefficient, β ３ : Cubic Dresselhaus coefficient, v Ｆ : Fermi velocity of electron, v ｄｒｉｆｔ : electron drift velocity, and is expressed by the following formula. That is, the wavelength λ during diffusion transport ｄｉｆｆ In contrast, the wavelength λ during drift transport has β ３ The Cubic term is added.

[0061] First, |α|+β>>6β ３ In the case of , the influence of the Cubic term can be ignored and λ = λ ｄｉｆｆ In the case of GaAs, |α|+β to 6β ３ Therefore, the influence of the Cubic term cannot be ignored, but v ｄｒｉｆｔ wo v ｄｒｉｆｔ / v Ｆ By suppressing the wavelength change due to drift to 0.1 or less, it can be said that the wavelength change due to drift can be ignored (vｄｒｉｆｔ / v Ｆ = 0.447, the wavelength shifts by 1 / 4). ＊ is the effective mass of an electron in GaAs, 0.067 × m, and the density of two-dimensional electrons is n = 4 × 10 １５ / m ２ Then the drift velocity is: Fermi wave number k Ｆ = (2πn) ０．５ v Ｆ = 2.7 x 10 ５ m / s and v ｄｒｉｆｔ / v Ｆ = 0.1 or less, v ｄｒｉｆｔ is 2.7 x 10 ４ m / s or less, for example, v ｄｒｉｆｔ = 1 x 10 ４ Let m / s.

[0062] The gate region is defined as ｄｒｉｆｔ In the case of drift transport, the gate length L is L≧v ｄｒｉｆｔ × t, it is considered possible to filter the signal while it is passing through the gate. In the case of the GaAs quantum well mentioned above, t = 0.154 ns, so v ｄｒｉｆｔ = 1 x 10 ４ m / s, L≧1×10 ４ ×0.154×10 －９ =1.54 μm, that is, shorter than the diffusion length, so the same gate length is sufficient.

[0063] The gate length L required to receive the effect of SOI within the gate for a response time of t seconds can be summarized as follows: 1. When the Cubic term does not need to be considered (no wavelength change due to drift), a) In the case of drift transport from input to output, L = v ｄｒｉｆｔ × t b) In the case of drift transport + diffusion transport from input to output, L = v ｄｒｉｆｔ ×t+(2D ｓ ×t) ０．５ 2. When it is necessary to consider the Cubic term (wavelength change due to drift), c) In the case of drift transport from the input to the center of the gate, diffusive transport after stopping for t seconds, and drift transport from the center of the gate to the output, L = (2D ｓ ×t) ０．５

[0064] [Fourth Embodiment] A filtering method using the electron spin wave filter of the first embodiment is as follows: ２ -t １ is the response time.

[0065] Time t ０ Then, with a drift voltage applied between the first ohmic electrode and the second ohmic electrode, multiple electron spin waves are input to the first portion (input portion).

[0066] Time t ０ ~t １ With a drift voltage applied between the first ohmic electrode and the second ohmic electrode for a period of time, the multiple electron spin waves are drift-transported from the first portion to the entrance of the gate region.

[0067] Time t １ ~t ２ During this period, a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the multiple electron spin waves are filtered while being drift-transported from the entrance to the exit of the gate region.

[0068] Time t ２ ~t ３ During this period, while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, electron spin waves are drift-transported from the exit of the gate region to the second portion (output section).

[0069] Here, the first portion is located between the first ohmic electrode and the gate electrode, and the second portion is located between the gate region and the second ohmic electrode.

[0070] Fifth Embodiment A filtering method using the electron spin wave filter of the first embodiment is as follows: ２ -t １ is the response time.

[0071] Time t １ Then, with a drift voltage applied between the first ohmic electrode and the second ohmic electrode, polarized light is irradiated to generate multiple electron spin waves in the third portion (input portion).

[0072] Time t １ ~t ２ During this period, a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the multiple electron spin waves are filtered while being drift-transported to the exit of the gate region.

[0073] Time t ２ ~t ３ During this period, while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, electron spin waves are drift-transported from the exit of the gate region to the second portion (output section).

[0074] Here, the third portion is located in the gate region, and the second portion is located between the gate region and the second ohmic electrode.

[0075] Sixth Embodiment A filtering method using the electron spin wave filter of the second embodiment is as follows: ２ -t １ is the response time.

[0076] Time t ０ Then, with a drift voltage applied between the first ohmic electrode and the second ohmic electrode, multiple electron spin waves are input to the fourth portion (input portion).

[0077] Time t ０ ~t １ During this period, the third ohmic electrode and the fourth ohmic electrode are opened while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the multiple electron spin waves are drift-transported from the fourth portion to the gate region.

[0078] Time t １ ~t ２ During this period, the third ohmic electrode and the fourth ohmic electrode are short-circuited while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the multiple electron spin waves are filtered while being transported by diffusion in the gate region.

[0079] Time t ２ ~t ３During this period, the third ohmic electrode and the fourth ohmic electrode are opened while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the filtered electron spin waves are drift-transported from the gate region to the fifth portion (output portion).

[0080] Here, the fourth portion is located between the first ohmic electrode and the third ohmic electrode, and the fifth portion is located between the fourth ohmic electrode and the second ohmic electrode.

[0081] Seventh Embodiment A filtering method using the electron spin wave filter of the second embodiment is as follows: ２ -t １ is the response time.

[0082] Time t １ Then, with a drift voltage applied between the first ohmic electrode and the second ohmic electrode, polarized light is irradiated to generate multiple electron spin waves in the sixth portion (input portion).

[0083] Time t １ ~t ２ During this period, the third ohmic electrode and the fourth ohmic electrode are short-circuited while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the multiple electron spin waves are filtered while being diffused and transported in the gate region.

[0084] Time t ２ ~t ３ During this period, the third ohmic electrode and the fourth ohmic electrode are opened while a drift voltage is applied between the first ohmic electrode and the second ohmic electrode, and the electron spin waves are drift-transported from the gate region to the fifth portion (output portion).

[0085] Here, the sixth portion is located in the gate region, and the fifth portion is located between the gate region and the second ohmic electrode.

[0086] In the fourth to seventh embodiments, the input position may be adjacent to the above-mentioned position, as long as the distance W between the input position and the output position along the gate electrode is greater than L.

[0087] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and treatment processes, and that such modifications are also within the scope of the present invention.

[0088] When understanding the abstract technical ideas of the embodiments and modifications, the technical ideas should not be interpreted as being limited to the contents of the embodiments and modifications. The above-described embodiments and modifications are merely illustrative examples, and many design modifications, such as changes, additions, and deletions of components, are possible. In the embodiments, the contents in which such design modifications are possible are emphasized by adding the notation "embodiment." However, design modifications are also permitted even in contents not so notated.

[0089] The technology of the present disclosure is applicable to fields such as optical communications, photoelectric conversion systems, and network computers.

[0090] REFERENCE SIGNS LIST 1: Electron spin wave filter, 2: Electron spin wave filter, 3: Demultiplexer, 10: One-dimensional wire structure, 11: Gate electrode, 12: First ohmic electrode, 13: Second ohmic electrode, 14: Third ohmic electrode, 15: Fourth ohmic electrode, 16: Switching element, 20: Input section, 21: Output section, 30: One-dimensional wire structure, 31: Input section, 41: First electron spin wave filter, 42: Second electron spin wave filter, 43: Third electron spin wave filter, 411: Gate electrode, 421: Gate electrode, 431: Gate electrode, 412: Output section, 422: Output section, 432: Output section.

Claims

1. One-dimensional nanowire structures through which electron spin waves propagate, A gate electrode along a part of the aforementioned one-dimensional nanowire structure, A first ohmic electrode is positioned upstream of the gate electrode and makes ohmic contact with the one-dimensional nanowire structure, A second ohmic electrode is positioned downstream of the aforementioned gate electrode and makes ohmic contact with the one-dimensional nanowire structure, Equipped with, An electron spin wave filter that, upon input of an electron spin wave having multiple wavelengths included in a first wavelength range, outputs only electron spin waves having wavelengths included in the first wavelength range and in a second wavelength range that is narrower than the first wavelength range, wherein An electron spin wave filter characterized in that the length of the gate electrode is greater than or equal to the length necessary to output only the electron spin wave having a wavelength included in the second wavelength range, which is affected by spin-orbit interaction within the one-dimensional nanowire structure along the gate electrode when an electric field is applied between the first ohmic electrode and the second ohmic electrode to drift transport the electron spin wave, and less than or equal to 200 μm.

2. A one-dimensional nanowire structure on which electron spin waves propagate, A gate electrode along a part of the aforementioned one-dimensional nanowire structure, A first ohmic electrode is positioned upstream of the gate electrode and makes ohmic contact with the one-dimensional nanowire structure, A second ohmic electrode is positioned downstream of the aforementioned gate electrode and makes ohmic contact with the one-dimensional nanowire structure, A third ohmic electrode is positioned between the first ohmic electrode and the gate electrode and makes ohmic contact with the one-dimensional nanowire structure, A fourth ohmic electrode is disposed between the gate electrode and the second ohmic electrode and makes ohmic contact with the one-dimensional nanowire structure, A switching element that switches the connection between the third ohmic electrode and the fourth ohmic electrode between an on state and an off state, Equipped with, An electron spin wave filter characterized in that, when an electron spin wave having multiple wavelengths included in a first wavelength range is input, it outputs only electron spin waves having wavelengths included in the first wavelength range and in a second wavelength range that is narrower than the first wavelength range.

3. The electron spin wave filter according to claim 1 or 2, characterized in that the one-dimensional nanowire structure is a semiconductor quantum well.

4. The spin diffusion coefficient of the aforementioned one-dimensional nanowire structure at a temperature of 15 K is 0.02 m ２ The electron spin wave filter according to claim 1 or 2, characterized in that it is ≥ / s.

5. The electron spin wave filter according to Claim 1, characterized in that when the bandwidth of the electron spin wave filter is Δq x (m - 1), the spin diffusion constant of the material constituting the one-dimensional nanowire structure is D s (m 2 / s), and the drift velocity of the electron spin wave due to the application of the electric field is v drift, the length of the gate electrode along the one-dimensional nanowire structure is v drift × 2ln(2) / (D s × (Δq x) 2) or more and 200 μm or less.

6. The electron spin wave filter according to claim 2, characterized in that when the bandwidth of the electron spin wave filter is Δq x (μm - 1), the length of the gate electrode along the one-dimensional nanowire structure is 2(ln(2)) 0.5 / Δq x or more and 200 μm or less.

7. A demultiplexer that branches a one-dimensional nanowire structure into multiple branches, with an electron spin wave filter at each branch point, The electron spin wave filter comprises a one-dimensional nanowire structure on which electron spin waves propagate, a gate electrode along a part of the one-dimensional nanowire structure, a first ohmic electrode positioned upstream of the gate electrode and in ohmic contact with the one-dimensional nanowire structure, and a second ohmic electrode positioned downstream of the gate electrode and in ohmic contact with the one-dimensional nanowire structure, or An electron spin wave filter comprising: a one-dimensional nanowire structure on which electron spin waves propagate; a gate electrode along a part of the one-dimensional nanowire structure; a first ohmic electrode disposed upstream of the gate electrode and in ohmic contact with the one-dimensional nanowire structure; a second ohmic electrode disposed downstream of the gate electrode and in ohmic contact with the one-dimensional nanowire structure; a third ohmic electrode disposed between the first ohmic electrode and the gate electrode and in ohmic contact with the one-dimensional nanowire structure; a fourth ohmic electrode disposed between the gate electrode and the second ohmic electrode and in ohmic contact with the one-dimensional nanowire structure; and a switching element that switches the connection between the third ohmic electrode and the fourth ohmic electrode between an on state and an off state, wherein When an electron spin wave having multiple wavelengths included in a first wavelength range is input, only electron spin waves having wavelengths included in the first wavelength range and in a second wavelength range narrower than the first wavelength range are output from the first electron spin wave filter located at an arbitrarily selected first branch destination, and only electron spin waves included in the first wavelength range and in a third wavelength range narrower than the first wavelength range are output from the second electron spin wave filter located at an arbitrarily selected second branch destination. A demultiplexer characterized in that there is no overlap between the second wavelength range and the third wavelength range.

8. A method for filtering electron spin waves using the electron spin wave filter described in claim 1, The steps include applying a voltage between the first ohmic electrode and the second ohmic electrode, The steps of: injecting an electron spin wave having multiple wavelengths included in the first wavelength range into a first region located between the first ohmic electrode and the gate electrode of the one-dimensional nanowire structure, or irradiating the first region with polarized light to generate an electron spin wave having multiple wavelengths included in the first wavelength range; The steps include: transporting the electron spin wave along the one-dimensional nanowire structure by drift; The steps include outputting only electron spin waves having wavelengths included in the second wavelength range from a second region located between the gate electrode and the second ohmic electrode of the one-dimensional nanowire structure, A filtering method characterized by including

9. A method for filtering electron spin waves using the electron spin wave filter described in claim 1, The steps include applying a voltage between the first ohmic electrode and the second ohmic electrode, The steps include: irradiating a third portion along the gate electrode of the one-dimensional nanowire structure with polarized light to generate electron spin waves having multiple wavelengths included in the first wavelength range; The steps include: transporting the electron spin wave along the one-dimensional nanowire structure by drift; The steps include outputting only electron spin waves having wavelengths included in the second wavelength range from a second region located between the gate electrode and the second ohmic electrode of the one-dimensional nanowire structure, A filtering method characterized by including

10. A method for filtering electron spin waves using the electron spin wave filter described in claim 2, The steps include applying a voltage between the first ohmic electrode and the second ohmic electrode, The steps include turning off the switching element, A step of injecting an electron spin wave having multiple wavelengths included in the first wavelength range into a fourth region located between the first ohmic electrode and the third ohmic electrode of the one-dimensional nanowire structure, or generating an electron spin wave having multiple wavelengths included in the first wavelength range by irradiating the fourth region with polarized light, The electron spin wave is transported by drift through the one-dimensional nanowire structure, The steps include turning on the switching element to cause the electron spin wave to spread and transport, The steps include: turning off the switching element after a predetermined time has elapsed and drift transporting the electron spin wave; The steps include outputting only electron spin waves having wavelengths included in the second wavelength range from a fifth region located between the fourth ohmic electrode and the second ohmic electrode of the one-dimensional nanowire structure, A filtering method characterized by including

11. A method for filtering electron spin waves using the electron spin wave filter described in claim 2, The steps include applying a voltage between the first ohmic electrode and the second ohmic electrode, The steps include: irradiating a sixth portion along the gate electrode with polarized light to generate an electron spin wave having multiple wavelengths included in the first wavelength range; The steps include: turning on the switching element to cause diffusion transport of the electron spin wave; and turning off the switching element after a predetermined time has elapsed to cause drift transport of the electron spin wave. The steps include outputting only electron spin waves having wavelengths included in the second wavelength range from a fifth region located between the fourth ohmic electrode and the second ohmic electrode of the one-dimensional nanowire structure, A filtering method characterized by including

12. The spin diffusion coefficient of the aforementioned one-dimensional nanowire structure at the filtering operating temperature is 0.02 m ２ The filtering method according to claim 10 or 11, characterized in that the time interval is 0.1 ns or more and the predetermined time interval is 0.1 ns or more and 1 μs or less.

13. The spin diffusion coefficient of the aforementioned one-dimensional nanowire structure at the filtering operating temperature is 0.05 m ２ The filtering method according to claim 10 or 11, characterized in that the time interval is 0.1 ns or more and the predetermined time interval is 0.1 μs or more and 0.1 μs or less.