A three-dimensional topological insulator spin plasma detection device

Abstract

The present invention provides a three-dimensional topological insulator spin plasma detection device, which includes: S1, preparing a coupling grating on the surface of a sample to be detected; S2, continuously irradiating the coupling grating with terahertz light, irradiating the reflection area with a detection polarized laser, and obtaining a detection polarized laser carrying the oscillation information of the reflection area; S3, after polarization beam splitting the detection polarized laser carrying the oscillation information of the reflection area, measuring the light signal intensity of each separated light beam, when the light signal intensity of each separated light beam is different, spin wave oscillation occurs on the surface of the sample to be detected. The present invention uses terahertz light to excite surface plasma of special materials, and uses a method of laser to detect the spin wave characteristics of the plasma oscillation to realize a spin wave detection process based on the magneto-optical Kerr effect. This technology effectively forms a propagation-type Dirac plasmon, fills the gap in the current spin wave detection means, and is of great significance for the generation and utilization of spin plasmons.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a three-dimensional topological insulator spin plasma detection device. Background Art

[0002] Spin-plasmons, as a collective oscillation phenomenon involving electron spins, has attracted widespread attention in recent years for its unique physical properties and potential application value. This phenomenon originates from the collective motion of electron spins under the excitation of an external electromagnetic field, which causes plasma fluctuations and realizes the organic combination of plasma oscillations and spin waves. In advanced technology fields such as spintronic devices and quantum computing, spin plasmas show great application prospects.

[0003] Among many material systems, graphene, topological insulator surface states and other materials have become ideal platforms for studying spin plasmons due to their special electronic structures and spin properties. A large number of literature has reported on the successful observation of spin plasma phenomena in these material systems, as well as preliminary explorations of their potential applications. However, current spin plasma observation technology still has certain limitations, mainly reflected in the reliance on excitation confined oscillation waves and the inadequacy of in-situ observation using absorption spectroscopy.

[0004] Specifically, existing spin plasma observations are mainly limited by the excitation-localized oscillation waves, which are limited in propagation in space, resulting in restrictions on the application scope of spin plasma. In addition, since spin waves decay rapidly in non-excited regions, in-situ absorption spectroscopy observation methods are difficult to capture complete spin plasma signals, which undoubtedly increases the difficulty of observation. More importantly, the non-propagation of spin oscillation waves makes their detection and utilization in practical applications face huge challenges, which greatly limits the development of spin plasma technology. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the propagation of oscillation waves in space is limited, resulting in the difficulty in observing spin plasma, and to provide a three-dimensional topological insulator spin plasma detection device.

[0006] In order to solve the above technical problems, the present invention provides a three-dimensional topological insulator spin plasma detection device, which includes: a carrying mechanism, in which a sample to be detected is arranged in the carrying mechanism, and the sample to be detected includes a body, a grating area and a reflection area, and the grating area and the reflection area are respectively arranged on the surface of the body, wherein the grating area is set as a coupling grating; a laser emitting mechanism, the laser emitting mechanism includes a laser emitter and a second beam splitter, and the second beam splitter divides the light source of the laser emitter into at least two light paths; an excitation mechanism, the excitation mechanism is arranged between the sample to be detected and the laser light source, and includes a terahertz emitter, and a light path in the laser light source reaches the coupling grating through the terahertz emitter; a detection mechanism, the detection mechanism includes a polarizer, a first beam splitter, a polarization beam splitter and a balanced detector, and the light in the laser light source Another light path passes through the polarizer and irradiates the reflection area, so that the detection polarized laser carrying the oscillation information of the reflection area is split by the polarization beam splitter and then input into the two probe ends of the balanced detector respectively; the detection process includes: step S1, dividing the grating area and the reflection area on the surface of the sample to be detected, and preparing a coupling grating in the grating area; step S2, continuously irradiating the coupling grating with terahertz light, and at the same time, irradiating the reflection area with the detection polarized laser to obtain the detection polarized laser carrying the oscillation information of the reflection area; step S3, after polarization splitting the detection polarized laser carrying the oscillation information of the reflection area, respectively measure the light signal intensity of each separated light beam, when the light signal intensity of each separated light beam is the same, it is considered that no spin wave oscillation occurs on the surface of the sample to be detected; when the light signal intensity of each separated light beam is different, it is considered that spin wave oscillation occurs on the surface of the sample to be detected.

[0007] In one embodiment of the present invention, in step S1, the sample to be detected is a three-dimensional topological insulator Bi2Se3 thin film, the thickness of which is not less than 300nm, the grating area and the reflection area have the same area, and the coupling grating period is 400-700nm.

[0008] In one embodiment of the present invention, step S1 specifically comprises: firstly growing a three-dimensional topological insulator Bi2Se3 thin film by molecular beam epitaxy, and then making a coupled grating on the grating region by electron beam etching and electron beam evaporation.

[0009] In one embodiment of the present invention, in step S2: the terahertz light is guided to the coupling grating, until the Dirac plasmon is excited in the grating area to form a spin wave, and when the sample to be detected undergoes spin wave oscillation, the grating area transmits the spin wave to the reflection area.

[0010] In one embodiment of the present invention, in step S2, the detection polarization laser is a pulsed laser with a wavelength of 750-800 nm; a pulse duration of less than 100 femtoseconds, and a repetition frequency of 75-85 MHz.

[0011] In one embodiment of the present invention, in step S2, before the detection polarized laser beam is split, the detection polarized laser is subjected to fixed frequency modulation and noise filtering in sequence.

[0012] In one embodiment of the present invention, it also includes step S4, creating an optical path difference between the terahertz light and the detection polarized laser to generate a time delay between the two, and when the spin wave oscillates in the sample to be detected, the relationship between the spin wave and time is calculated through the time delay.

[0013] In one embodiment of the present invention, the detection mechanism also includes an optical chopper and a phase-locked amplifier. The optical chopper is arranged on the transmission light path between the second beam splitter and the polarizer. The phase-locked amplifier is arranged at the output end of the balanced detector and is connected to the optical chopper signal.

[0014] In one embodiment of the present invention, the excitation mechanism further includes at least one spherical reflector; the detection mechanism further includes a movable reflective component and at least one fixed reflector, and the movable reflective component moves relative to at least one of the fixed reflectors.

[0015] In one embodiment of the present invention, the movable reflective assembly comprises a slide rail, a driver and a movable reflective mirror, and the movable reflector is connected to one end of the slide rail to drive the movable reflective mirror to move along the slide rail.

[0016] In one embodiment of the present invention, it also includes a central control system, and the detection mechanism is connected to the central control system.

[0017] The above technical solution of the present invention has the following advantages compared with the prior art:

[0018] The three-dimensional topological insulator spin plasma detection device described in the present invention uses terahertz light to excite surface plasma of special materials, and uses a laser to detect the spin wave characteristics of the plasma oscillation to realize a spin wave detection process based on the magneto-optical Kerr effect. This invention technology can effectively excite the electrons in the surface state of the material to be detected to form a propagating Dirac plasmon, and detect the corresponding spin oscillation waves, which fills the gap in current spin wave detection methods and has important enlightenment and guiding significance for the generation and utilization of spin plasmons. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0020] Figure 1 is a schematic diagram of the structure of a sample to be detected in a preferred embodiment of the present invention;

[0021] Figure 2 It is a schematic structural diagram of a three-dimensional topological insulator spin plasma detection device in a preferred embodiment of the present invention;

[0022] Figure 3 yes Figure 2 Schematic diagram of the structure of the movable reflective component and the fixed reflector.

[0023] Explanation of the reference numerals in the specification: 100, supporting mechanism; 110, sample stage; 120, sample to be detected; 121, main body; 122, grating area; 123, reflection area; 200, laser emitting mechanism; 210, laser emitter; 220, first beam splitter; 300, excitation mechanism; 310, terahertz emitter; 320, spherical reflector; 400, detection mechanism; 410, fixed reflector; 420, movable reflector assembly; 421, slide rail; 422, driver; 423, movable reflector; 430, optical chopper; 440, polarizer; 450, second beam splitter; 460, polarization beam splitter; 470, balanced detector; 480, phase-locked amplifier; 490, computer. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0025] Example

[0026] See also Figure 1 and Figure 2 As shown, this embodiment provides a three-dimensional topological insulator spin plasma detection device, which is used to perform spin plasma detection of a three-dimensional topological insulator Bi2Se3 film, and includes:

[0027] A carrying mechanism 100, in which a sample 120 to be detected is disposed. The sample 120 to be detected includes a body 121, a grating region 122, and a reflection region 123. The grating region 122 and the reflection region 123 are respectively disposed on the surface of the body 121, wherein the grating region 122 is configured as a coupling grating;

[0028] An excitation mechanism 300, which is disposed between the sample to be detected 120 and the laser light source, and includes a terahertz emitter 310, through which a beam of light in the laser light source reaches the coupling grating;

[0029] The detection mechanism 400 includes a polarizer 440, a first beam splitter 220, a polarization beam splitter 460 and a balanced detector 470. After another light beam in the laser light source passes through the polarizer 440, it irradiates the reflection area 123 through the first beam splitter 220, so that the detection polarized laser carrying the oscillation information of the reflection area is split by the polarization beam splitter 460 and then input into the two probe ends of the balanced detector 470 respectively.

[0030] The three-dimensional topological insulator spin plasma detection device described in this embodiment uses terahertz light to excite the plasma on the surface of the three-dimensional topological insulator Bi2Se3 film, and uses a laser to detect the spin wave characteristics of the plasma oscillation to realize a spin wave detection process based on the magneto-optical Kerr effect. This invention technology can effectively excite the electrons in the surface state of the material to be detected to form a propagating Dirac plasmon, and detect the corresponding spin oscillation waves, which fills the gap in the current spin wave detection means and has important enlightenment and guiding significance for the generation and utilization of spin plasmons.

[0031] In this embodiment, the carrier mechanism 100 also includes a sample stage 110, and the three-dimensional topological insulator Bi2Se3 film is placed on the sample stage 110. Specifically, the sample stage 110 in this embodiment is preferably a liquid helium refrigeration stage, which can be used to accommodate a sample to be tested with a size of 1cm×1cm. In other embodiments, other low-temperature sample stages 110 can also be selected, and this application does not make specific restrictions on this. Further, in this embodiment, the light-transmitting window of the sample stage 110 needs to be able to simultaneously transmit 3-5THz (60-100um) and 780nm short-wave infrared lasers, thereby adapting to the subsequent detection process.

[0032] See also Figure 1As shown, the sample 120 to be detected in this embodiment is obtained by molecular beam epitaxy. To ensure the detection quality, its thickness needs to reach 300nm or more. Further, the grating area 122 and the reflection area 123 in this embodiment are arranged on the same surface of the body 121, wherein the coupling grating is made on the grating area 122 by a method combining electron beam lithography (E-beam lithography) and electron beam evaporation (E-beam evaporation), thereby providing a platform for exciting propagating Dirac plasmons with a specific oscillation period. Furthermore, the period of the coupling grating in this embodiment is 400-700nm, wherein the width of any metal grid and the width of the gap are half of its period, thereby generating a relatively uniform optical response, thereby improving its use stability. At the same time, the uniform distribution of metal grids and gaps helps to enhance the coupling of electromagnetic fields on the grating surface, thereby improving the efficiency of optical devices.

[0033] See also Figure 2 As shown, this embodiment further includes a laser emitting mechanism 200, the laser emitting mechanism 200 includes a laser emitter 210 and a second beam splitter 450, the second beam splitter 450 divides the light source of the laser emitter 210 into at least two light paths, one of which is an excitation light path passing through the excitation mechanism 300, and the other is a detection light path passing through the excitation mechanism 300. Specifically, the laser emitter 210 in this embodiment can generate a pulsed laser with a wavelength of 780nm, a pulse duration of less than 100 femtoseconds, and a repetition frequency of 80MHz.

[0034] In this embodiment, the excitation mechanism 300 further includes two spherical mirrors 320, and the excitation light path of the terahertz emitter 310 is guided by the two spherical mirrors 320 to guide the transmission direction of the light path. Specifically, in this embodiment, a femtosecond pulse laser beam generated by the laser emitter 210 enters the terahertz emitter 310 to generate parallel terahertz pulse radiation, and then reaches the coupling grating in the sample to be detected 120 under the guidance of the spherical mirror 320, so as to achieve the excitation of the Dirac plasmon in the surface state of the topological insulator. Specifically, the working principle of the terahertz emitter 310 in this embodiment is: the irradiation of the high-speed pulse laser generates electron-hole pairs in the semiconductor crystal (GaAs or InGaAs material grown at low temperature) inside it, and then these photoexcited carriers are accelerated by the applied external electric field, and the physical separation of electrons and holes forms a macroscopic field opposite to the bias electric field. The rapid rise and decay of the electric field generates a transient current, which in turn generates an electromagnetic radiation pulse with the same or similar frequency in the terahertz frequency range.

[0035] Furthermore, in this embodiment, when the terahertz pulse radiation reaches the coupled grating in the sample to be detected 120, a specific electron spin arrangement will be generated on the grating region 122 of the sample to be detected 120, and the polarization state and intensity of the light reflected from the surface of the material with the specific electron spin arrangement will change. Therefore, this change can be detected by the magneto-optical Kerr effect MOKE to intuitively infer the spin wave state of the material surface.

[0036] See also Figure 2 As shown, the detection polarized laser passes through the first beam splitter 220 and is transmitted to the polarization beam splitter 460 and reaches the reflection area 123. At this time, its polarization state and intensity will change, so it can be confirmed that there are spin waves on the surface of the material to be detected. Next, the detection polarized laser carrying the oscillation information of the reflection area reaches the polarization beam splitter 460, and the polarization beam splitter 460 separates the different light signals. Therefore, by comparing the light signal intensities of each light beam after separation, it can be known whether there are spin oscillations on the surface of the sample 120 to be detected, as well as the relative intensity of the spin oscillations.

[0037] Furthermore, the detection mechanism 400 further includes a mobile reflection component 420 and at least one fixed reflection mirror 410, and the mobile reflection component 420 moves relative to at least one fixed reflection mirror 410. In this embodiment, based on the setting of the mobile reflection component 420, the present application can reflect the spin wave intensity, phase and other information of the sample 120 to be detected by comparing the changes in the light beam state at different positions and under different excitation-detection time delay conditions. Specifically, see Figure 3 As shown, the mobile reflective assembly 420 in this embodiment includes a slide rail 421, a driver 422 and a mobile reflector 423. The mobile reflector is connected to one end of the slide rail 421 to drive the mobile reflector 423 to move along the slide rail 421. During the transmission of the detection light path, the displacement direction and size of the mobile reflective assembly 420 can be used to achieve micron-level control of the optical path of the entire detection light path. Furthermore, in this embodiment, as the mobile reflector 423 moves, a micron to millimeter optical path difference can be generated between the detection light path and the excitation light path, thereby generating a femtosecond level delay. It should be noted that in actual operation, the actual position of the fixed reflector 410 for receiving the light reflected by the mobile reflector 423 will be adjusted accordingly with the mobile reflector 423 to ensure that the subsequent light path is not affected.

[0038] See also Figure 2As shown, the detection mechanism 400 in this embodiment also includes an optical chopper 430 and a phase-locked amplifier 480. The optical chopper 430 is arranged on the transmission optical path between the second beam splitter 450 and the polarizer 440. The phase-locked amplifier 480 is arranged at the output end of the balanced detector 470 and is connected to the optical chopper 430 signal. The optical chopper 430 generates a frequency modulation on the detection optical path laser by periodically covering the light source, and the modulation frequency is synchronously input into the phase-locked amplifier 480. Further, after the detection laser passes through the material surface and passes through the polarization beam splitter 460, it is divided into two beams of light with perpendicular polarization states, and is guided to the two ends of the balanced detector 470 at the same time. The balanced detector 470 can output the signal difference of the two beams of orthogonal polarized light. The signal generated by the balanced detector 470 is introduced into the phase-locked amplifier 480, so as to minimize the noise in the process of extracting the signal information of the modulation frequency of the optical chopper 430. Furthermore, the present application also includes a central control system 490, the detection mechanism 400 is connected to the central control system 490, the modulation signal generated by the optical chopper 430 is input from the phase-locked amplifier 480 to the central control system 490, and the optical signal is read, thus completing a complete detection process. The driver 422 is also connected to the central control system 490 to facilitate the adaptive adjustment of the reflective moving component. Specifically, the central control system 490 is preferably a computer.

[0039] The specific detection process of this embodiment includes the following steps:

[0040] Step S1, divide the surface of the sample 120 to be detected into a grating area 122 and a reflection area 123, and prepare a coupling grating in the grating area 122; in this embodiment, the sample 120 to be detected is a three-dimensional topological insulator Bi2Se3 film, whose thickness is not less than 300nm, the grating area 122 and the reflection area 123 have the same area, and the coupling grating period is 400-700nm. Further, in the above process, the three-dimensional topological insulator Bi2Se3 film is first grown by molecular beam epitaxy, and then the coupling grating is made on the grating area 122 by electron beam etching and electron beam evaporation.

[0041] Step S2, continuously irradiate the coupling grating with terahertz light, and at the same time, irradiate the reflection area with the detection polarization laser to obtain the detection polarization laser carrying the oscillation information of the reflection area; in this embodiment, the detection polarization laser is a pulsed laser with a wavelength of 750-800nm; its pulse duration is less than 100 femtoseconds, and the repetition frequency is 75-85MHz. Specifically, the terahertz light is guided to the coupling grating, and the Dirac plasmon is excited in the grating area 122 to form a spin wave. When the spin wave oscillates in the sample 120 to be detected, the grating area 122 transmits the spin wave to the reflection area 123. Furthermore, in step S2, before the detection polarization laser is split, the detection polarization laser is sequentially subjected to fixed frequency modulation and noise filtering.

[0042] Step S3, after polarization splitting the mixed light beam, respectively measure the light signal intensity of each separated light beam,

[0043] When the light signal intensities of the separated light beams are the same, it is considered that no spin wave oscillation occurs on the surface of the sample 120 to be detected;

[0044] When the light signal intensities of the separated light beams are different, it is considered that spin wave oscillation occurs on the surface of the sample 120 to be detected;

[0045] This embodiment also includes step S4, creating an optical path difference between the terahertz light and the detection polarized laser to generate a time delay between the two, and calculating the time-dependent relationship of the spin wave when the spin wave oscillates in the sample to be detected 120. In addition, the irradiation position of the detection beam can be controlled by moving the reflective component 420, thereby generating an intensity map of the spin wave under a certain time delay state.

[0046] In summary, the three-dimensional topological insulator spin plasma detection device described in the present invention uses terahertz light to excite surface plasma of special materials, and uses laser to detect the spin wave characteristics of the plasma oscillation to realize the spin wave detection process based on the magneto-optical Kerr effect. This invention technology can effectively excite the electrons in the surface state of the material to be detected to form propagating Dirac plasmons, and detect the corresponding spin oscillation waves, which fills the gap in current spin wave detection methods and has important enlightenment and guiding significance for the generation and utilization of spin plasmons.

[0047] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A three-dimensional topological insulator spin plasma detection device, characterized in that: include: A carrying mechanism, in which a sample to be detected is arranged, the sample to be detected comprises a body, a grating area and a reflection area, the grating area and the reflection area are respectively arranged on the surface of the body, wherein the grating area is arranged as a coupling grating; A laser emitting mechanism, the laser emitting mechanism comprising a laser emitter and a second beam splitter, the second beam splitter splitting the light source of the laser emitter into at least two light paths; An excitation mechanism, which is disposed between the sample to be detected and the laser light source and includes a terahertz emitter, through which a beam of light in the laser light source reaches the coupling grating; A detection mechanism, the detection mechanism includes a polarizer, a first beam splitter, a polarization beam splitter and a balanced detector, another light path of the laser light source passes through the polarizer and then irradiates the reflection area, so that the detection polarization laser carrying the oscillation information of the reflection area is split by the polarization beam splitter and then respectively input into two probe ends of the balanced detector; The detection process includes: Step S1, dividing the surface of the sample to be detected into a grating area and a reflection area, and preparing a coupling grating in the grating area; Step S2, continuously irradiating the coupling grating with terahertz light, and at the same time irradiating the reflection area with detection polarized laser light, thereby obtaining detection polarized laser light carrying oscillation information of the reflection area; Step S3, after polarization splitting the detection polarized laser light carrying the oscillation information of the reflection area, respectively measure the optical signal intensity of each separated light beam, When the light signal intensities of the separated light beams are the same, it is considered that no spin wave oscillation occurs on the surface of the sample to be detected; When the light signal intensities of the separated light beams are different, it is considered that spin wave oscillation occurs on the surface of the sample to be detected.

2. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: In step S1, the sample to be detected is a three-dimensional topological insulator Bi2Se3 thin film, the thickness of which is not less than 300nm, the grating area and the reflection area have the same area, and the coupling grating period is 400-700nm.

3. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: Step S1 specifically comprises: firstly growing a three-dimensional topological insulator Bi2Se3 thin film by molecular beam epitaxy, and then manufacturing a coupled grating on the grating region by electron beam etching and electron beam evaporation.

4. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: In step S2: the terahertz light is guided to the coupling grating, until the Dirac plasmon is excited in the grating area to form a spin wave, and when the sample to be detected undergoes spin wave oscillation, the grating area transmits the spin wave to the reflection area.

5. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: In step S2, the detection polarization laser is a pulsed laser with a wavelength of 750-800 nm; a pulse duration of less than 100 femtoseconds, and a repetition frequency of 75-85 MHz.

6. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: In step S2, before the detection polarized laser beam is split, the detection polarized laser is subjected to fixed frequency modulation and noise filtering in sequence.

7. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: It also includes step S4, creating an optical path difference between the terahertz light and the detection polarized laser to generate a time delay between the two, and calculating the relationship between the spin wave and time through the time delay when the spin wave oscillates in the sample to be detected.

8. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: The detection mechanism also includes an optical chopper and a phase-locked amplifier. The optical chopper is arranged on the transmission light path between the second beam splitter and the polarizer. The phase-locked amplifier is arranged at the output end of the balanced detector and is connected to the optical chopper signal.

9. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: The excitation mechanism also includes at least one spherical reflector; the detection mechanism also includes a movable reflective component and at least one fixed reflector, and the movable reflective component moves relative to at least one of the fixed reflectors.

10. The three-dimensional topological insulator spin plasma detection device according to claim 9, characterized in that: The movable reflective assembly comprises a slide rail, a driver and a movable reflective mirror. The movable reflector is connected to one end of the slide rail to drive the movable reflective mirror to move along the slide rail.

11. The three-dimensional topological insulator spin plasma detection device according to claim 1, characterized in that: It also includes a central control system, and the detection mechanism is connected to the central control system.

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