Electron spin wave multiplex transmission method and electron spin wave multiplex transmission device

Abstract

To provide a multiple transmission and separate detection method of electron spin waves.SOLUTION: The present invention is characterized that the superposition of multiple electron spin waves is performed and multiple electron spin waves are transmitted in a solid-state electronic device having a semiconductor quantum well structures by utilizing the permanent spin-swirling state in the crystal orientation dependence of the effective magnetic field due to spin-orbit interaction generated in semiconductor quantum well structures, and by controlling the amplitude, phase, and polarization degrees of freedom of the electron spin wave.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the multiplexing of electron spin waves. Transmission Method It also relates to a multiplex transmission device for electron spin waves. [Background technology]

[0002] In modern society, opportunities to handle large amounts of information are increasing, with the advent of 5G (5th generation mobile communication system), AI (artificial intelligence), and IoT (Internet of Things). Currently, the main means of transmitting information is "light," and long-distance, large-capacity transport is achieved using optical fibers. Light waves have the characteristics of "parallelism" (no interference with each other) and "multiplexity" (the ability to superimpose waves). For this reason, wavelength division multiplexing (WDM), which applies these characteristics, has made it possible to transmit multiple pieces of information simultaneously over a single optical fiber.

[0003] On the other hand, in electronic devices such as semiconductor integrated circuits, it is in principle impossible to transmit multiple pieces of information simultaneously. This is because the properties of electrons are significantly different from those of light, and parallelism and multiplexing cannot be incorporated. However, if electronic devices that also have the characteristics of light are realized, it may be possible to realize a diverse information processing platform on a single information carrier, with the coexistence of analog and digital signals and the mixing of von Neumann and non-von Neumann type calculations. Therefore, the inventors believe that "electron spin waves" can be used as this ultimate information carrier.

[0004] Electron spin waves can be generated by the effective magnetic field generated by the spin-orbit interaction existing inside a semiconductor. For example, there are two types of spin-orbit interactions in a III-V semiconductor quantum well structure: the effective magnetic field generated by the Rashba spin-orbit interaction (the clockwise arrow in Figure 6(a)) and the Dresselhaus spin-orbit interaction (the arrow in Figure 6(b)). When these two effective magnetic fields are equal, the direction of the effective magnetic field is oriented in a single axial direction (arrow shown in Figure 6(c)), the effective magnetic field direction is fixed, and spin relaxation is suppressed. This state can be called a permanent spin rotation state. As the electron spin rotates around this effective magnetic field, a wave of electron spin is generated as shown in Figure 7. In Figure 7, λ + =+(1 / q 0 ) relationship. In FIG. 0 means a wave number specific to the material. By satisfying this condition, electron spin waves can exist stably in the semiconductor, making it possible to create an information carrier that uses electron spin waves.

[0005] An electron spin wave is a phenomenon in which the spin of an electron, which has the magnetic properties of an electron, propagates through space while changing direction, and has classical "wave" properties. As shown in Figure 7, the length of one rotation of an upward spin from a downward spin to an upward spin again can be defined as the wavelength λ of the electron spin wave. This wavelength can be used as information, and by treating different wavelengths as different information, it is possible to transmit multiplexed information using electron spin waves. Therefore, information as light waves can be directly transferred into a solid. Since electron spin waves can exist stably in a state where spin relaxation is suppressed, it is believed that they can propagate long distances and that their wavelength can be freely controlled depending on the strength of the effective magnetic field. Furthermore, it may be possible to superpose electron spin waves by controlling the amplitude, phase, and polarization degrees of freedom. In other words, since electron spin waves have the same properties as light, it may be possible to realize multiplexed transmission of information, which has been achieved with optical fibers, in solid-state electronic devices.

[0006] The present inventors have previously studied the above-mentioned electron spin waves, and published part of the research results on electron spin waves in Non-Patent Document 1 below. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Y. Kunihashi, M. Kohda, J. Nitta, et al, “Drift transport of helical spin coherence with tailored spin-orbit interactions”, NATURE COMMUNICATIONS, Published 8 Mar 2016. Summary of the Invention [Problem to be solved by the invention]

[0008] One problem with the WDM method mentioned above is that the more information to be transmitted simultaneously, the more photoelectric conversion devices must be prepared, raising concerns about increased volume and power consumption.In contrast, a transmission method using electron spin waves is thought to be able to seamlessly realize parallel information processing by generating multiple spin wave signals by directly transferring multiple optical signals to semiconductors. This will make it possible to suppress an increase in the number of devices, and is expected to lead to increased speeds due to the parallelism and multiplexing of waves.

[0009] The present invention has been made based on the background explained above, and aims to provide a technology that uses electron spin waves, making it possible to treat continuous changes in spin direction accompanying spin rotation as an analog signal, and enables simultaneous processing of digital information and analog information. [Means for solving the problem]

[0010] (1) Multiplexing of electron spin waves according to the present invention Transmission Method utilizes the permanent spin orbit state in the crystal orientation dependence of the effective magnetic field due to the spin-orbit interaction that occurs in semiconductor quantum well structures, applying an electromagnetic field to the semiconductor quantum well structure by a gate electrode to control an effective magnetic field due to spin-orbit interaction of the semiconductor quantum well structure; Amplitude, phase, and phase of electron spin waves or Polarization freedom The gate voltage applied to the gate electrodeThe present invention is characterized in that a plurality of electron spin waves are superimposed by controlling the frequency of the electron spin waves, and the plurality of electron spin waves are transmitted in the solid-state electronic device having the semiconductor quantum well structure.

[0011] (2) The present invention The multiplex transmission method of electron spin waves according to (1) The solid-state material having the semiconductor quantum well structure electronic In the device, an electron spin wave having a wavelength equal to a specific wavelength uniquely determined by the strength of the spin-orbit interaction is transmitted, and an electron spin wave having a wavelength different from the specific wavelength uniquely determined by the strength of the spin-orbit interaction is eliminated, thereby electronic The device transmits only electron spin waves with a specific wavelength. It is preferred.

[0012] (3) In the method of multiplexing electron spin wave transmission according to the present invention described in (1) or (2), when the number of electron spin waves is large, it is preferable to perform a fast Fourier transform on the data obtained by real space measurement to convert it into wave number space data and analyze it. (4) The electron spin wave multiplex transmission device according to the present invention comprises a solid-state electronic device having a semiconductor quantum well structure capable of generating electron spin waves, a circuit having a cross portion including the semiconductor quantum well structure, a gate electrode capable of applying an electromagnetic field to the cross portion by a gate voltage, and a power supply connected to the gate electrode, and comprises means for transmitting electron spin waves to the circuit by utilizing a permanent spin orbit state in the crystal orientation dependence of the effective magnetic field due to spin-orbit interaction, and a means for transmitting an electromagnetic field generated by a gate voltage applied to the gate electrode to the semiconductor quantum well structure. well the gate voltage being applied to a structure to control an effective magnetic field due to spin-orbit interaction of the semiconductor quantum well structure, and the amplitude, phase, or polarization degree of freedom of the electron spin wave being controlled by the gate voltage, thereby superimposing a plurality of electron spin waves, and transmitting a plurality of electron spin waves along the circuit having the semiconductor quantum well structure. (5) In the electron spin wave multiplex transmission device according to the present invention described in (4), it is preferable that the device has a function of transmitting only electron spin waves having specific wavelengths by eliminating electron spin waves having wavelengths different from a specific wavelength that is uniquely determined by the strength of spin-orbit interaction in the multiple electron spin waves during transmission. (6) In the multiplex transmission device of electron spin waves according to the present invention, the circuit in one direction in the cross portion indicates a direction parallel to

[0110] in the crystal of the semiconductor quantum well structure, and the circuit in the other direction in the cross portion indicates semiconductor The thickness direction of the cross portion is parallel to the

[0110] direction in the quantum well structure crystal. semiconductor It is preferable that the direction be parallel to the crystal

[0001] of the quantum well structure. Effect of the Invention

[0013] According to the present invention, the amplitude, phase, and polarization degree of freedom of the electron spin wave can be controlled, thereby enabling multiplexed transmission of the electron spin wave. Each multiplexed electron spin wave contains continuous analog signal information such as amplitude and phase in addition to digital signal information of 0 and 1 due to up and down spins, making it possible to process digital and analog information simultaneously. This has the effect of making it possible to switch between von Neumann and non-von Neumann type calculations. [Brief description of the drawings]

[0014] [Figure 1] 1(a) shows a spin wave generated by a Monte Carlo simulation, in which FIG. 1(a) is a diagram showing a first example of the spin distribution of up spins and down spins in real space, FIG. 1(b) is a diagram showing the state obtained by applying a Fourier transform to the state shown in FIG. 1(a), FIG. 1(c) is a diagram showing a second example of the spin distribution of up spins and down spins in real space, FIG. 1(d) is a diagram showing the state obtained by applying a Fourier transform to the state shown in FIG. 1(c), FIG. 1(e) is a diagram showing a third example of the spin distribution of up spins and down spins in real space, and FIG. 1(f) is a diagram showing the state obtained by applying a Fourier transform to the state shown in FIG. 1(e). [Diagram 2] This figure shows the case of a stable long-wavelength spin wave excited at time 0, where the spin wave has a wavelength equal to the intrinsic wavelength (λ0=9.0 μm) that is uniquely determined by the strength of the spin-orbit interaction in a solid. [Diagram 3] This figure shows spin waves excited at time 0 with a specific wavelength (λ0=9.0 μm) that is uniquely determined by the strength of the spin-orbit interaction in a solid and a different wavelength (λ0=4.5 μm), and shows the case of unstable short-wavelength spin waves. [Figure 4] FIG. 1 shows the time evolution of spin distribution when spin waves of different wavelengths are incident on the same solid. [Diagram 5] This figure shows drift transport of multiple spin waves and electron spin wave filters. Fig. 5(a) is a cross-section at Y=0 of the real space distribution of the multiple spin waves shown in Fig. 5(b). Fig. 5(b) is a diagram showing the real space distribution of multiple spin waves having three wavelength components, λ1=20μm, λ2=6.7μm, and λ3=3.3μm. Fig. 5(c) is a diagram showing the reciprocal space distribution of multiple spin waves having the same three wavelength components. Fig. 5(d) shows the drift transport in the +Y direction when the multiple waves shown in Fig. 5(b) are incident on a region where λ2 is stable. FIG. 5(e) shows the state when the multiple waves shown in FIG. 5(c) are incident on an area where λ2 is stably present and are drift-transported in the +Y direction for 1 ns. FIG. 5(f) shows the state when the multiple waves shown in FIG. 5(b) are incident on an area where λ3 is stably present and are drift-transported in the +Y direction for 1 ns. FIG. 5(g) shows the state when the multiple waves shown in FIG. 5(c) are incident on an area where λ3 is stably present and are drift-transported in the +Y direction for 1 ns. [Figure 6] These are diagrams to explain two types of spin-orbit interactions that exist in III-V semiconductor quantum well structures. Figure 6(a) shows the Rashba spin-orbit interaction, Figure 6(b) shows the Dresselhaus spin-orbit interaction, and Figure 6(c) shows the permanent spin orbit state. [Figure 7] FIG. 1 is an explanatory diagram illustrating the concept of electron spin waves. [Figure 8]FIG. 1 is an explanatory diagram showing an example of a circuit configuration capable of multiplexing and transmitting electron spin waves. [Figure 9] 9 is a graph showing that a large effective magnetic field exceeding 10 T can be generated by controlling the gate voltage in the circuit configuration shown in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand. First, the technique for superposing electron spin waves will be described. The wavelength of electron spin waves changes depending on the strength of the effective magnetic field resulting from the spin-orbit interaction that occurs in semiconductor quantum well structures. Since each unique wavelength corresponds one-to-one to the information being transmitted, the inventors believed that it would be possible to distinguish information by examining the wavelength of the spin waves.

[0016] The inventors have found that it is possible to change the strength of the effective magnetic field by controlling the gate voltage using a gate structure formed on the semiconductor surface, and that spin waves of any wavelength can be generated. Furthermore, in two-dimensional electron gas in a semiconductor quantum structure, the wavelength of the spin wave changes depending on the in-plane crystal orientation. In a state of permanent spin rotation, as shown in Figure 6(c), the effective magnetic field experienced by electrons moving in a specific crystal orientation can be made zero. Therefore, by restricting the direction of electron motion using a fine wire structure or the like, it is possible to change the wavelength of a stably existing spin wave from a specific value to infinity (plane wave). This makes it possible to control the amplitude, phase, and polarization degree of freedom of the electron spin wave.

[0017] A typical material capable of generating electron spin waves is a III-V group compound semiconductor quantum well structure, and a layered structure such as that shown in Table 1 can be adopted. However, materials capable of generating similar electron spin waves include II-VI group semiconductors and SrTiO in addition to III-V group semiconductors. 3 / LaAlO3 This can be realized in a variety of materials, including SiGe quantum wells. In addition, various crystal orientations can be used, more specifically, the crystal orientations described in D. Iizasa et al., Physical Review B, 101, (2020), 245417. For example, the configuration shown in Table 1 below can be adopted. In Table 1, QW indicates a quantum well structure.

[0018] [Table 1]

[0019] The following literature describes electron spin waves in Yoji Kunihashi et al. "Drift-Induced Enhancement of Cubic Dresselhaus Spin-Orbit Interaction in a Two-Dimensional Electron Gas" Physical Review Letter 119, 187703 (2017). As shown in Fig. 2(a) on page 3 of the above-mentioned document, it is explained that the wavelength of the electron spin wave changes depending on the drift velocity of the electron, that is, the energy possessed by the electron. Based on this knowledge, it is possible to generate different wavelengths of spin waves by exciting electron spins with different electronic energies with light. Specifically, it is possible to generate multiple spin waves by superimposing and exciting circularly polarized light of different wavelengths. In a method other than the above, a ferromagnet / semiconductor junction can be used to generate spin-polarized electrons in a semiconductor by performing electrical spin injection from a ferromagnet to a semiconductor. In the above-mentioned structure, the electron spin polarization and electron density can be changed depending on the applied bias voltage, so in principle it is possible to generate the spatial distribution of electron spin polarization and electron density created by multiple electron spin waves in a semiconductor by changing the bias voltage of electrical spin injection.

[0020] In the present application, a circuit equivalent to the circuit shown in FIG. 1 of the above-mentioned document can be applied. Figure 8 is an explanatory diagram showing a circuit equivalent to the circuit shown in Figure 1 of the same document. The cross part 1 in this circuit has a laminated structure shown in Table 1, and an electric field can be applied in the x or y direction of Figure 8 by fabricating a Hall bar structure. In the circuit of FIG. 8, each width of the cross portion 1 is formed to be 250 μm. The laminated portions at the four corners of the cross portion 1 are ohmic contacts connected to the wiring 2a or wiring 3a connected to the power source 2 or power source 3, and are connected to the x-direction voltage V x , voltage in the y direction V y The voltages indicated by the arrows can be applied. Furthermore, a Cr / Au thin film (gate electrode) 5 is deposited in the region shown by the rectangular frame (region surrounded by a rectangular frame with a width of 300 μm in both directions) so as to include the intersection of the cross portion 1, and a gate voltage (V g ) can be applied. The size of each part of the circuit can also be made equivalent to that of the circuit diagram in Figure 1 of the same document. In the structure in Figure 8, by thinning the film thickness of the quantum well structure as shown in Table 1, it can be considered as a structure in which the movement of electrons is restricted from three dimensions to two dimensions, and the duration of the spin waves that appear here can be understood. The strength of the high-order Dresselhaus magnetic field depends on the crystal orientation when confining it in two dimensions. It is possible to draw a Monte Carlo simulation from this circuit.

[0021] The Monte Carlo simulation was performed using the latest version (R2020b) of "Matlab," a calculation software made by Math Works. The time evolution when the electron spin senses the effective magnetic field and precesses can be described by the Bloch equation. For this reason, after generating spin polarization at t = 0, the position information and spin components of the electron spin are updated using the equation consisting of the parameters listed in Table 2 below, and the analysis was performed as follows.

[0022] For example, in the circuit shown in Figure 8, the area enclosed by the dashed line is used as the gate structure, and the gate voltage (V g ) can be applied to this gate structure. g ) is applied to the area enclosed by the rectangular frame. g It is possible to form electron spin waves corresponding to the spin-orbit interaction generated by V. g By changing the value of , different electron spin waves can be generated, so V g By controlling the value of , any wavelength can be produced. In Fig. 8, the x direction is the [1 1 The y direction indicates the direction parallel to the

[0110] of the crystal of the quantum well structure, and the z direction indicates the direction parallel to the

[0001] of the crystal of the quantum well structure. In addition, the overbars attached to the Miller indices written in the brackets [ ] indicating the above-mentioned crystal directions are written as underbars instead because the format cannot be expressed in a patent specification. As mentioned above, the gate voltage (V gThe technology for generating an effective magnetic field capable of generating different electron spin waves by changing the value of θ, is described in a paper previously published by the present inventors: Makoto Kohda, et al., “Enhancement of spin-orbit interaction and the effect of interface diffusion in quaternary InGaAsP / InGaAs heterostructures,” Physical Review B 81, 115118 (2010). For example, Figure 9 shows the relationship between the gate voltage and the effective magnetic field described in the above-mentioned literature, and shows that by precisely controlling the gate voltage, it is possible to apply an effective magnetic field exceeding 10 T (tesla). The results in Figure 9 show that In 0.52 Al 0.48 As layer (thickness 200 nm), InGaAsP layer (thickness 5 nm), In 0.8 Ga 0.2 As layer (thickness 10 nm), InGaAlAs layer (thickness 3 nm), In 0.52 Al 0.48 The results were obtained for a stacked structure including an As layer (thickness 25 nm).

[0023] Figure 1 shows the superposition of electron spin waves generated in different directions. Monte Carlo simulation was used to generate the electron spin waves, and the specific parameters are shown in Table 2 below. The upper figures in FIG. 1 are inverse spaces (wave number spaces) obtained by performing a two-dimensional Fourier transform on the lower figures in FIG. 1, and show wave numbers, which are the reciprocals of wavelengths. FIG. 1(a) shows a first example of the spin distribution of up spins and down spins in real space, and FIG. 1(b) shows the inverse space (wave number space) obtained by applying a two-dimensional Fourier transform to the state shown in FIG. 1(a). In Figure 1(a), three vertical rows of spin distributions are shown distributed in the left-right direction, while of the three rows in the top-bottom direction, the central distribution indicates an area with a high proportion of up spin, and the top and bottom two distributions indicate areas with a high proportion of down spin.

[0024] FIG. 1(c) shows a second example of the spin distribution of up spins and down spins in real space, and FIG. 1(d) shows the inverse space (wave number space) obtained by applying a two-dimensional Fourier transform to the state shown in FIG. 1(c). Figure 1(c) shows three horizontal rows of spin distributions distributed in the vertical direction. Of the three rows, the central distribution indicates an area with a high proportion of up spin, while the two distributions on the left and right indicate areas with a high proportion of down spin. As can be seen in Figures 1(a) and (c), the direction of the electron spin wave changes depending on the direction of the spin-orbit interaction. The two-dimensional Fourier transform is a program that can transform two-dimensional matrices using a fast Fourier transform algorithm. In principle, it is equivalent to performing a fast Fourier transform twice in the x and y directions.

[0025] FIG. 1(e) shows a third example of the spin distribution of up spins and down spins in real space, and FIG. 1(f) shows the inverse space (wave number space) obtained by applying a two-dimensional Fourier transform to the state shown in FIG. 1(e). In Figure 1(e), areas with a high proportion of up spin are distributed to the left and right of the area with a high proportion of up spin, and there are areas with a high proportion of down spin on the four sides, above and below, and above and below.

[0026] If the wavelength of the electron spin wave is λ, then a peak appears at the position of wave number q, with a magnitude of q = 2π / λ. Figure 1(e) is a superposition of the waveforms of Figure 1(a) and Figure 1(c), and Figure 1(f), which is the Fourier transform of Figure 1(e), maintains the peak positions of Figure 1(b) and Figure 1(d). This means that electron spin waves have parallelism and multiplicity just like normal waves. The results shown in Figure 1 show that when two types of electron spin waves are superimposed, they superimpose while maintaining their own wavelengths (wave numbers). This proves that electron spin waves have parallelism and multiplicity, just like light, and can be superimposed without interfering with each other. As shown in Figures 1(b), (d), and (e), if the spin distribution is understood in the reciprocal space (wave number space) after a two-dimensional Fourier transform, the spin distribution can be understood more clearly than when the spin distribution is understood in real space. Therefore, when two types of electron spin waves are superimposed, each electron spin wave can be superimposed while maintaining its own wavelength (wave number), and when multiple electron spins are superimposed and transmitted, they can be transported without interfering with each other, and it was also found that the waves can be superimposed as electron spin waves. Therefore, electron spin waves can be transmitted using wavelength division multiplexing, just like light.

[0027] [Table 2]

[0028] In Table 2, α is the strength of the Rashba spin-orbit interaction, β 1 :Strength of Dresselhaus spin-orbit coupling (linear term), β 3 : indicates the strength of the Dresselhaus spin-orbit interaction (cubic term), Ds: spin diffusion constant, Ns: carrier density, g: g factor, Electrons: number of electrons, μ: electron mobility, Eex: external electric field. In all cases, no external magnetic field is applied. The simulation is performed assuming that electrons are scattered in random directions every 10 ps.

[0029] "Multiplexed information transmission and separate detection" Next, a method for transmitting the generated multiple electron spin waves and a method for separating and detecting them will be described. The inventors have discovered that electron spin waves can be transported while maintaining their waveform by appropriately using a drift electric field and an external magnetic field (S. Anghel, et al. "Spin-locked transport in a two-dimensional electron gas", Physical Review B 101, 155414(2020)). Furthermore, it was found that by setting the strength of the spin-orbit interaction in a solid to a specific value, it is possible to stably retain only spin waves with a specific wavelength calculated from the strength of the interaction, while eliminating other wavelength components.

[0030] 2 to 4 show the time evolution when electron spin waves with different wavelengths are generated in semiconductors having the same strength of spin-orbit coupling. In Figure 2, since the material has the same inherent wavelength determined by the strength of the spin-orbit interaction, the state is stable and the material can maintain its shape for a long time. On the other hand, in Fig. 3, the wavelength is different from the inherent wavelength determined by the strength of the spin-orbit interaction of the semiconductor, and so the shape is lost in a short time. Figure 4 compares the two, and shows that the stable spin wave shown in Fig. 2 can maintain the Z-direction spin wave for a certain period of time, unlike the unstable spin wave shown in Fig. 3. This means that only the stable spin wave can be maintained and transmitted, and the unstable spin wave can be attenuated and eliminated. The semiconductor assumed in FIGS. 2 to 4 is a semiconductor having the parameters set in Table 2 above.

[0031] Figure 2 shows the characteristic wavelength (λ ) that is uniquely determined by the strength of the spin-orbit interaction in a solid. 0 In Fig. 3, electron spin waves of a different wavelength (λ = 4.5 μm) are excited at time 0. Figure 2 maintains its shape for a long time, but Figure 3 loses its shape due to the spin relaxation mechanism. From the above, it can be said that if the strength of the spin-orbit interaction can be freely controlled, it will be possible to select and extract only the information contained in spin waves of any wavelength. This means that only stable spin waves (wavelength: λ 0 This means that they have created a spin wave filter that can retain and transmit unstable spin waves (spin waves with a wavelength of λ=9.0 μm) and attenuate and eliminate unstable spin waves (spin waves with a wavelength of λ=4.5 μm). In a semiconductor quantum well structure, the strength of the Rashba spin-orbit interaction and the Dresselhaus spin-orbit interaction is uniquely determined by the structure, such as the quantum well width. The wavelength of a spin wave is inversely proportional to the sum of the strengths of these two types of spin-orbit interactions, so once a quantum structure is determined, the wavelength of the spin wave specific to the material that constitutes that structure is uniquely determined. In this study, for semiconductors with spin-orbit interactions of the strengths listed in Table 2, λ 0 = 9.0 μm is the most stable spin wave.

[0032] As an example, Figure 5 shows a calculation example that uses this principle to generate a state in which three spin waves are superimposed and transported by a drift electric field, thereby extracting only stable spins. The strength of the spin-orbit interaction is determined so that only electron spin waves with a specific wavelength are stable, and three waves are generated, including the stable spin wave. Specifically, FIG. 1 = 20μm, λ 2 = 6.7μm, λ 3 = 3.3 μm, and is transported in the +Y direction while tracking its time evolution.

[0033] As described in the previous section, the wavelength (λ) of a spin wave is inversely proportional to the strength of the spin-orbit interaction. Therefore, it is possible to control the strength of the spin-orbit interaction in a material by controlling the gate voltage, for example, and select the most stable wavelength of the spin wave. In a Monte Carlo simulation, an electron spin wave with three wavelength components was created by inputting the z component (Sz) of the electron spin spreading according to a Gaussian distribution at t = 0 into the following formula as a function of position. A specific function is expressed as Sz(X) = cos(2π × 0.05 × X) + 1.5 cos(2π × 0.15 × X) + 0.7 cos(2π × 0.3 × X) (X: position [μm]).

[0034] Fig. 5(d) and (e) show the λ 2 Assuming that the semiconductor has a spin-orbit coupling strength that makes the wavelength stable, λ 3 We assumed that the semiconductor has a spin-orbit coupling strength such that the wavelength is stable. Fig. 5(b) and (c) show the λ 1 = 20μm, λ 2 = 6.7μm, λ 3 5(a) shows the real space and reciprocal space distributions of multiple spin waves having three wavelength components at Y=0 in FIG. 5(b). This multiple wave is called λ 2 The results are shown in Fig. 5(d) and (e). 3 Figures 5(f) and (g) show the results when the beam was injected into a region where it is stable. In these figures, it can be seen that the spin waves are changing their shape as they move in the +Y direction as a whole. At this time, components other than the stable wavelengths disappear over time, making it possible to extract only specific wavelength components from the multiple waves of electron spins. This shows that it is possible to transport spin waves of different wavelengths in a superimposed state, while simultaneously extracting only specific wavelength components. In other words, it was found that by locally modulating the strength of the spin-orbit interaction at a specific location using an electron spin wave filter, it is possible to freely change the waveform of the electron spin wave passing through that location by drift transport.

[0035] In the above explanation, the strength of the spin-orbit coupling at a particular point is, for example, the gate voltage (V g ) is proportional to V g The strength of the spin-orbit interaction can be determined from the value of . Also, "local modulation" means that only the gate electrode forming region in the circuit of Fig. 8 is modulated, and the region where the gate electrode is not formed is not modulated. In addition, the drift transport occurs when the gate voltage (V x ) can be applied to the circuit to move electrons from the left to the right by the electric field. This is the meaning of drift transport, and it is explained that the electrons pass from the region where the gate electrode 5 is not formed through the region where the gate electrode 5 is formed, and then pass through the region on the opposite side where the gate electrode is not formed.

[0036] From the above explanation, it has been demonstrated that it is possible to superpose a plurality of electron spin waves by utilizing the permanent spin rotation state in the crystal orientation dependence of the effective magnetic field due to spin-orbit interaction generated in a semiconductor quantum well structure and controlling the amplitude, phase, and polarization degree of freedom of the electron spin wave, and further that it is possible to transmit a plurality of electron spin waves in a solid-state electronic device having the semiconductor quantum well structure. Furthermore, in a solid-state device having a semiconductor quantum well structure (the circuit described above), by transmitting electron spin waves of a wavelength equal to a specific wavelength that is uniquely determined by the strength of the spin-orbit interaction, and eliminating electron spin waves of a wavelength different from the specific wavelength that is uniquely determined by the strength of the spin-orbit interaction, it was demonstrated that only electron spin waves of a specific wavelength can be transmitted in a solid-state device. Furthermore, when there are a large number of electron spin waves, it was found that by performing a fast Fourier transform on the data obtained by real-space measurements and bringing it into wave number space data for analysis, it is possible to easily confirm how the spin waves change shape as they move. In this case, it was also demonstrated that it is possible to extract only specific wavelength components from the multiple waves, since components other than the stable wavelengths disappear over time. [Explanation of symbols]

[0037] 1...cross circuit, 2, 3...power supply, 2a, 3a...wiring, 5...gate electrode layer, 6...power supply, V g : Gate voltage, V x : Voltage applied in the x direction, V y : Voltage applied in the y direction.

Claims

1. A method for multiplexing electron spin waves, characterized in that it utilizes a permanent spin rotation state in the crystal orientation dependence of an effective magnetic field due to spin-orbit interaction generated in a semiconductor quantum well structure, applies an electromagnetic field to the semiconductor quantum well structure by a gate electrode, controls the effective magnetic field due to the spin-orbit interaction of the semiconductor quantum well structure, and controls the amplitude, phase, or polarization degree of freedom of the electron spin wave by a gate voltage applied to the gate electrode, thereby superimposing a plurality of electron spin waves, and transmits a plurality of electron spin waves in a solid-state electronic device having the semiconductor quantum well structure.

2. The method for multiplexing electron spin waves as described in claim 1, characterized in that, in the solid-state electronic device having the semiconductor quantum well structure, electron spin waves of a wavelength equal to a specific wavelength uniquely determined from the strength of the spin-orbit interaction are transmitted, and electron spin waves of a wavelength different from the specific wavelength uniquely determined from the strength of the spin-orbit interaction are eliminated, thereby transmitting only electron spin waves having a specific wavelength in the solid-state electronic device.

3. A method for multiplexing transmission of electron spin waves as described in claim 1 or 2, characterized in that when there are a large number of electron spin waves, data obtained by real space measurement is subjected to fast Fourier transform to be converted into wave number space data and analyzed.

4. A solid-state electronic device having a semiconductor quantum well structure capable of generating electron spin waves, the circuit having a cross portion including the semiconductor quantum well structure, a gate electrode capable of applying an electromagnetic field to the cross portion by a gate voltage, and a power source connected to the gate electrode, A means for transmitting electron spin waves to the circuit by utilizing a permanent spin orbit state in the crystal orientation dependence of an effective magnetic field due to spin-orbit interaction; an electromagnetic field generated by a gate voltage applied to the gate electrode is applied to the semiconductor quantum well structure, an effective magnetic field due to the spin-orbit interaction of the semiconductor quantum well structure is controlled, and the amplitude, phase, or polarization degree of freedom of the electron spin wave is controlled by the gate voltage, thereby superimposing a plurality of electron spin waves, and a multiple electron spin wave transmission device is provided which transmits a plurality of electron spin waves along the circuit having the semiconductor quantum well structure.

5. The electron spin wave multiplex transmission device according to claim 4, characterized in that it has the function of transmitting only electron spin waves having a specific wavelength by eliminating electron spin waves having a wavelength different from a specific wavelength uniquely determined by the strength of spin-orbit interaction among the multiple electron spin waves during transmission.

6. 6. An electron spin wave multiplex transmission device as described in claim 4 or claim 5, characterized in that a circuit in one direction in the cross portion indicates a direction parallel to [110] in the crystal of the semiconductor quantum well structure, a circuit in the other direction in the cross portion indicates a direction parallel to [110] in the crystal of the semiconductor quantum well structure, and a thickness direction of the cross portion indicates a direction parallel to [001] in the crystal of the semiconductor quantum well structure.

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