A spin terahertz emitter and a chiral regulation method and a preparation method thereof

Abstract

The application discloses a spin terahertz emitter and a chiral regulation method and a preparation method thereof, and belongs to the field of terahertz emission. The spin terahertz emitter is a three-layer structure including a ferromagnetic material layer, a non-ferromagnetic material layer and an antiferromagnetic layer. The antiferromagnetic layer adopts a preset crystal phase NiO single crystal antiferromagnetic material, CrSb or Mn3Sn. Under the irradiation of a femtosecond laser, the antiferromagnetic layer generates a laser impact magnetic moment. The precession of the laser impact magnetic moment generates a spin polarization current. The spin polarization current is injected into the non-ferromagnetic layer to generate a transient charge current, and then radiate terahertz, thereby realizing efficient spin terahertz radiation. Further, the magnetic moment direction of the ferromagnetic material layer in the spin terahertz emitter is reversed by rotating the direction of an external magnetic field or by a spin-orbit moment effect, thereby realizing efficient regulation of terahertz chirality.

Description

Technical Field

[0001] This invention relates to the field of terahertz emission, and in particular to a spin terahertz emitter and its chiral control method and preparation method. Background Technology

[0002] For terahertz emission, commonly used THz sources include photoconductive antenna terahertz sources and other spin terahertz sources. The photoconductive antenna terahertz source consists of a semiconductor substrate and electrodes. Its working principle is that an ultrashort laser pulse is focused onto the semiconductor material between the electrodes. If the laser photon energy is greater than the band gap width of the semiconductor substrate, electrons can be excited into the conduction band to form photogenerated carriers. These photogenerated carriers move under the influence of a bias electric field, forming a transiently changing current within the laser penetration depth, thus radiating terahertz waves. The spin terahertz source is generally composed of a ferromagnetic / non-ferromagnetic heterojunction. Its working principle is that when a femtosecond laser pulse irradiates the ferromagnetic / non-ferromagnetic heterobilayer, an ultrafast spin current is excited in the ferromagnetic layer. When the spin current enters the heavy metal layer, the inverse spin Hall effect converts it into a transient charge current, thereby radiating terahertz waves.

[0003] Regarding the structure of spin terahertz emission, in 2018, Professor Jin Zuanming of Shanghai University proposed a high-efficiency terahertz emission chip based on electron spin and its fabrication method. This method uses a ferromagnetic layer / metal layer / oxide barrier layer / pinning layer / antiferromagnetic pinning layer as the basic emission structure. Without applying an external magnetic field, the terahertz radiation efficiency, bandwidth and polarization state can be controlled by controlling different materials and film thicknesses in the composite film structure. In 2020, the Institute of Physics at the University of Augsburg, Germany, achieved the control of terahertz amplitude by changing the direction of the external magnetic field in a structure of ferromagnetic layer / non-ferromagnetic layer / ferromagnetic layer / antiferromagnetic pinning layer and utilizing the tunneling magnetoresistance effect.

[0004] Regarding the generation of terahertz waves in antiferromagnetic / nonferromagnetic heterojunctions, Tsinghua University emitted terahertz waves in a Mn3Sn / Pt heterojunction in 2019. In 2021, Nanjing University successfully emitted spin terahertz waves in a Nio(111) / Pt(W) heterojunction and proved that the emission was independent of an external magnetic field. In 2022, Paris-Saclay University and the Free University of Berlin collaborated to realize terahertz radiation in NiO(001) / Pt.

[0005] However, existing technologies have the following drawbacks:

[0006] 1. Current antiferromagnetic terahertz experiments only focus on whether field-free emission is possible, without paying attention to the emission of chiral terahertz.

[0007] 2. There is currently no research on terahertz emission using antiferromagnetic / ferromagnetic / nonferromagnetic structures;

[0008] 3. Currently, there is no research on using spin orbital moment reversal to control the magnetic moment on this structure. Summary of the Invention

[0009] The purpose of this invention is to provide a spin terahertz emitter and its chiral control method and preparation method, which can realize efficient terahertz radiation and efficient and rapid chiral control based on spin materials.

[0010] To achieve the above objectives, the present invention provides the following solution:

[0011] A spin terahertz emitter, the spin terahertz emitter comprising: a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer;

[0012] A non-ferromagnetic material layer is disposed between the ferromagnetic material layer and the antiferromagnetic layer;

[0013] The antiferromagnetic layer is made of NiO single-crystal antiferromagnetic material with a preset crystal phase, CrSb or Mn3Sn.

[0014] Under femtosecond laser irradiation, the antiferromagnetic layer generates a laser-impact magnetic moment. The precession of the laser-impact magnetic moment generates a spin-polarized current. After the spin-polarized current is injected into the nonferromagnetic layer, it generates a transient charge flow, which then radiates terahertz waves.

[0015] A chiral modulation method for a spin terahertz transmitter, wherein the chiral modulation method applies the aforementioned spin terahertz transmitter, and the chiral modulation method includes:

[0016] Terahertz chirality can be controlled by reversing the direction of the magnetic moment of the ferromagnetic material layer in the spin terahertz transmitter by rotating the direction of the external magnetic field or by using the spin orbital moment effect.

[0017] A method for fabricating a spin terahertz transmitter includes:

[0018] A ferromagnetic thin film or an antiferromagnetic thin film is grown on a substrate; the antiferromagnetic thin film is a NiO thin film, a CrSb thin film or a Mn3Sn thin film.

[0019] Non-ferromagnetic thin films are grown on ferromagnetic or antiferromagnetic thin films;

[0020] An antiferromagnetic or ferromagnetic thin film is grown on a non-ferromagnetic thin film to form a three-layer film.

[0021] The three-layer film is annealed in an annealing furnace to obtain a spin terahertz emitter comprising a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer.

[0022] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0023] This invention discloses a spin terahertz emitter and its chiral control and fabrication method. The spin terahertz emitter has a three-layer structure comprising a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer. The antiferromagnetic layer is made of a NiO single-crystal antiferromagnetic material with a predetermined crystal phase, CrSb, or Mn3Sn. Under femtosecond laser irradiation, the antiferromagnetic layer generates a laser-impact magnetic moment. The laser-impact magnetic moment precession generates a spin-polarized current. After the spin-polarized current is injected into the non-ferromagnetic layer, a transient charge current is generated, which then radiates terahertz waves, achieving efficient spin terahertz radiation. Furthermore, by rotating the direction of the external magnetic field or by using the spin orbital moment effect to flip the direction of the magnetic moment of the ferromagnetic material layer in the spin terahertz emitter, efficient control of terahertz chirality is achieved. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The spin terahertz transmitter provided in Embodiment 2 of the present invention has a magnetic field angle of 90° in an external magnetic field. ° Schematic diagram of terahertz wave modulation at time;

[0026] Figure 2 The magnetic field angle of the spin terahertz transmitter provided in Embodiment 2 of the present invention relative to the external magnetic field is... Figure 1 The magnetic field direction changed 180 degrees ° Schematic diagram of terahertz wave modulation afterward;

[0027] Figure 3 Another spin terahertz transmitter provided in Embodiment 2 of the present invention has a magnetic field angle of 90° in the external magnetic field. ° Schematic diagram of terahertz wave modulation at time;

[0028] Figure 4 The magnetic field angle of another spin terahertz transmitter provided in Embodiment 2 of the present invention relative to the external magnetic field is... Figure 3 The direction of the magnetic field changed by 180 degrees. ° Schematic diagram of terahertz wave modulation afterward;

[0029] Figure 5 This is a schematic diagram of the terahertz wave modulation of a spin terahertz transmitter provided in Embodiment 2 of the present invention;

[0030] Figure 6 This is a schematic diagram of the terahertz wave modulation of another spin terahertz transmitter by the spin orbital moment effect provided in Embodiment 2 of the present invention;

[0031] Figure 7 This is a flowchart illustrating the fabrication method of the spin terahertz transmitter provided in Embodiment 3 of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The purpose of this invention is to provide a spin terahertz emitter and its chiral control method and preparation method, which can realize efficient terahertz radiation and efficient and rapid chiral control based on spin materials.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] This invention provides a spin terahertz transmitter, comprising: a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer. The non-ferromagnetic material layer is disposed between the ferromagnetic material layer and the antiferromagnetic layer. The antiferromagnetic layer is made of a NiO single-crystal antiferromagnetic material with a predetermined crystal phase, CrSb, or Mn3Sn.

[0037] Under femtosecond laser irradiation, the antiferromagnetic layer generates a laser-impact magnetic moment. The precession of the laser-impact magnetic moment generates a spin-polarized current. After the spin-polarized current is injected into the nonferromagnetic layer, it generates a transient charge flow, which then radiates terahertz waves.

[0038] The spin terahertz emitter of this invention is independent of the direction of the external magnetic field; that is, when the direction of the external magnetic field changes, the amplitude and phase of the emitted terahertz radiation remain unchanged. Highly efficient spin terahertz radiation can be achieved using antiferromagnetic / nonferromagnetic heterojunctions with specific crystalline phases, such as NiO(111) / Pt, NiO(001) / Pt, Mn3Sn(0001) / Pt, and CrSb(111) / Pt.

[0039] For example, the ferromagnetic material layer is made of a two-dimensional ferromagnetic material or a ferromagnetic metal. The non-ferromagnetic material layer is made of a topological material, including a topological insulator, a topological half-metal, or a heavy metal with a spin Hall angle greater than the Hall angle threshold.

[0040] This application employs a three-layer structure—a ferromagnetic layer, a non-ferromagnetic layer, and an antiferromagnetic layer—as a spin terahertz emitter. The antiferromagnetic layer utilizes a pre-defined crystal phase of NiO single-crystal antiferromagnetic material, CrSb, or Mn3Sn. The ferromagnetic layer uses two-dimensional ferromagnetic materials (FexGeTe2, CrTe2), ferromagnetic metals (Co, Fe, Ni, etc., and their alloys), and the non-ferromagnetic layer uses topological materials such as topological insulators (Bi2Se3, Bi2Te3, BixSb1-x, Sb2Te3, (BixSb1-x)2Te3, and their alloys), topological half-metals (PtTe2, WTe2), and heavy metals with large spin Hall angles (W, Ta, Pt, etc.) to fabricate a three-layer heterojunction spin terahertz source. The materials selected in this invention have a wide applicable temperature range and are stable within the temperature range of 0K to 300K, enabling wide-bandwidth, high-efficiency spin terahertz radiation and ensuring device reliability.

[0041] Furthermore, the spin terahertz emitter also includes a substrate. The substrate is disposed beneath a ferromagnetic material layer or an antiferromagnetic layer.

[0042] Figure 1 The spin terahertz emitter shown comprises, from bottom to top, a sapphire substrate, a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer. Figure 2 Another spin terahertz emitter is shown, which, from bottom to top, includes a sapphire substrate, an antiferromagnetic layer, a nonferromagnetic material layer, and a ferromagnetic material layer.

[0043] Example 2

[0044] This invention provides a chiral modulation method for a spin terahertz transmitter. The chiral modulation method applies the spin terahertz transmitter of Embodiment 1 and includes:

[0045] Terahertz chirality can be controlled by reversing the direction of the magnetic moment of the ferromagnetic material layer in the spin terahertz transmitter by rotating the direction of the external magnetic field or by using the spin orbital moment effect.

[0046] For example, the magnetic moment direction of the ferromagnetic material layer in a spin terahertz transmitter is reversed through the spin orbital moment effect, specifically by applying -30 MA / cm to the spin terahertz transmitter. 2 ~30MA / cm 2 The current is used to 180° adjust the magnetic moment direction of the ferromagnetic material layer in the spin terahertz transmitter. ° Flip it.

[0047] For example, the magnetic moment direction of the ferromagnetic material layer in the spin terahertz transmitter is reversed by rotating the direction of the external magnetic field. Specifically, this includes applying an external magnetic field of -200mT to 200mT to the spin terahertz transmitter and rotating the external magnetic field to reverse the magnetic moment direction of the ferromagnetic material layer in the spin terahertz transmitter.

[0048] The spin terahertz emitter was placed in a variable-temperature (0–300 K) terahertz time-domain spectroscopy system for performance testing. Within the experimental temperature range of 0 K–300 K, under irradiation with an 800 nm or 1560 nm femtosecond laser, the emitter was subjected to rotation of the magnetic field or the application of a -30 MA / cm² magnetic field. 2 ~30MA / cm 2 The current then flips the magnetic moment of the ferromagnetic layer through the spin orbital moment effect, thereby achieving the control of terahertz chirality.

[0049] Figures 1 to 4 In the diagram, the line connecting the two electrodes is in the x-direction, the femtosecond laser emitted from below the spin terahertz emitter is in the z-direction, and the line connecting the external magnetic fields NS is in the y-direction. Figure 1 and Figure 2 It can be seen that the direction of the magnetic field changed by 180 degrees. ° This allows for left-hand to right-hand control of terahertz polarization. (By...) Figure 3 and Figure 4 It can be seen that the direction of the magnetic field changed by 180 degrees. ° This enables the control of terahertz polarization from left-handed to right-handed.

[0050] Figure 5 and Figure 6 The effect of spin orbital moment on the terahertz wave modulation of two types of spin terahertz transmitters is shown.

[0051] This invention is based on the property of non-collinear antiferromagnetism. First, for an antiferromagnetic thin film with a specific crystal phase, taking the 111 crystal phase as an example, under femtosecond laser irradiation, the antiferromagnetic thin film generates a laser-impacted magnetic moment M through magnetic difference frequency, and the precession of M generates a spin-polarized current J. s1 After a spin current is injected into an adjacent nonferromagnetic layer, a transient charge flow J is generated due to the inverse spin Hall effect. c This process radiates terahertz waves, and this radiation method does not depend on the direction of the external magnetic field. That is, when the direction of the external magnetic field changes, the amplitude and phase of the radiated terahertz waves remain unchanged.

[0052] In this invention, when the direction of the magnetic moment of the ferromagnetic layer is changed by altering the direction of the external magnetic field and the spin orbital moment effect, the terahertz phase radiated by the ferromagnetic / non-ferromagnetic heterojunction will also change accordingly. When the magnetic moment direction is changed by a rotating magnetic field, the picosecond charge flow J generated by the ferromagnetic / non-ferromagnetic heterojunction... c1Picosecond charge flow J generated by antiferromagnetic / nonferromagnetic heterojunction c2 This will generate an angle whose value is the rotation angle of the magnetic field, thus radiating terahertz waves with a certain phase difference in the x and y directions, where:

[0053] When the magnetic field angle of the external magnetic field is 0 ° Or 180 ° At that time, the terahertz waves emitted by the spin terahertz transmitter are linearly polarized.

[0054] When the magnetic field angle of the external magnetic field is greater than 0 ° Less than 180 ° And not equal to 90 ° When, or when the magnetic field angle of the external magnetic field is greater than 180° ° Less than 360 ° And not equal to 270 ° At that time, the spin terahertz transmitter radiates obliquely elliptical polarized terahertz waves.

[0055] When the magnetic field angle of the external magnetic field is equal to 90° ° Or 270 ° Furthermore, the picosecond charge flow J generated by the ferromagnetic / nonferromagnetic heterojunction c1 Picosecond charge flow J generated by antiferromagnetic / nonferromagnetic heterojunction c2 When they are not equal, the spin terahertz emitter radiates positively elliptically polarized radiation; the ferromagnetic / nonferromagnetic heterojunction is a heterojunction formed by a ferromagnetic material layer and a nonferromagnetic material layer; the antiferromagnetic / nonferromagnetic heterojunction is a heterojunction formed by an antiferromagnetic layer and a nonferromagnetic material layer.

[0056] When the magnetic field angle of the external magnetic field is equal to 90° ° Or 270 ° Furthermore, the picosecond charge flow J generated by the ferromagnetic / nonferromagnetic heterojunction c1 Picosecond charge flow J generated by antiferromagnetic / nonferromagnetic heterojunction c2 When they are equal, the spin terahertz transmitter radiates circularly polarized terahertz waves.

[0057] When the external magnetic field and the antiferromagnetic layer are at an angle to each other, and the external magnetic field rotates 180 degrees... ° Then, by controlling the terahertz wave with the opposite rotation direction, the conversion from left (right) spiral (elliptical) polarization to right (left) spiral (elliptical) polarization can be achieved.

[0058] Similarly, if the spin orbital moment effect is used to 180° adjust the magnetic moment of the ferromagnetic layer... ° By flipping the radiated terahertz wave, its rotation direction can also be changed, enabling rapid and efficient chiral control of the spin terahertz wave at the transmitting end. This invention can achieve efficient terahertz chiral control through multiple methods.

[0059] This invention has made significant innovations in terahertz emission and control methods, enabling on-chip ultrafast and low-power terahertz control.

[0060] Example 3

[0061] This invention provides a method for fabricating a spin terahertz transmitter, such as... Figure 7 As shown, it includes:

[0062] Step 1: Grow a ferromagnetic thin film or an antiferromagnetic thin film on a substrate; the antiferromagnetic thin film is a NiO thin film, a CrSb thin film or a Mn3Sn thin film.

[0063] Step 2: Grow a non-ferromagnetic thin film on a ferromagnetic thin film or an antiferromagnetic thin film.

[0064] Step 3: Grow an antiferromagnetic thin film or a ferromagnetic thin film on a non-ferromagnetic thin film to form a three-layer film.

[0065] Step 4: Anneal the three-layer film in an annealing furnace to obtain a spin terahertz emitter containing a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer.

[0066] In one example, the growth thickness of the ferromagnetic thin film ranges from 2 nm to 10 nm. The growth thickness of the antiferromagnetic thin film ranges from 15 nm to 100 nm. The growth thickness of the nonferromagnetic thin film ranges from 2 nm to 10 nm.

[0067] The methods for growing ferromagnetic thin films, antiferromagnetic thin films, and nonferromagnetic thin films include molecular beam epitaxy, magnetron sputtering, and pulsed laser deposition.

[0068] The detailed process of fabricating a spin terahertz transmitter is as follows:

[0069] Step 1: First, ferromagnetic thin films of 2 nm to 10 nm, such as two-dimensional ferromagnetic materials (FexGeTe2, CrTe2), ferromagnetic metals (Co, Fe, Ni, etc. and their alloys), or antiferromagnetic thin films with a thickness range of 15 nm to 100 nm are grown on double-polished alumina substrates or double-polished magnesium oxide substrates by growth methods such as molecular beam epitaxy, magnetron sputtering or pulsed laser deposition.

[0070] Step 2: Grow non-ferromagnetic thin films with a thickness range of 2nm to 10nm using growth methods such as molecular beam epitaxy, magnetron sputtering, or pulsed laser deposition. These include topological insulators (Bi2Se3, Bi2Te3, BixSb1-x, Sb2Te3, (BixSb1-x)2Te3 and their alloys), topological half-metals (PtTe2, WTe2), and heavy metals with large spin Hall angles (W, Ta, Pt, etc.).

[0071] Step 3: Grow antiferromagnetic thin films with a thickness range of 10 nm to 200 nm or ferromagnetic thin films with a thickness range of 2 nm to 10 nm using growth methods such as molecular beam epitaxy, magnetron sputtering or pulsed laser deposition, such as two-dimensional ferromagnetic materials (FexGeTe2, CrTe2) and ferromagnetic metals (Co, Fe, Ni and their alloys).

[0072] Step 4: Anneal the film at 800°C in an annealing furnace and apply a magnetic field of more than 1T, with the magnetic field direction along the x-direction.

[0073] This application proposes a spin terahertz emission mechanism based on antiferromagnetic / nonferromagnetic / ferromagnetic heterostructures, which achieves efficient terahertz radiation and efficient and rapid chiral control based on spin materials by using ordinary spin terahertz emission mechanisms, antiferromagnetic terahertz emission mechanisms, and spin orbital moment effects.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for chiral control of a spin terahertz transmitter, characterized in that, The chiral regulation method includes: The direction of the magnetic moment of the ferromagnetic material layer in the spin terahertz emitter is reversed by rotating the direction of the external magnetic field to achieve the control of terahertz chirality. The spin terahertz emitter includes: a ferromagnetic material layer, a non-ferromagnetic material layer, and an antiferromagnetic layer. The non-ferromagnetic material layer is disposed between the ferromagnetic material layer and the antiferromagnetic layer. The antiferromagnetic layer adopts a NiO single crystal antiferromagnetic material with a preset crystal phase, CrSb, or Mn3Sn. Under the irradiation of a femtosecond laser, the antiferromagnetic layer generates a laser-impacted magnetic moment. The precession of the laser-impacted magnetic moment generates a spin-polarized current. After the spin-polarized current is injected into the non-ferromagnetic layer, a transient charge flow is generated, which then radiates terahertz waves. The magnetic moment direction of the ferromagnetic material layer in the spin terahertz transmitter is reversed by rotating the direction of the external magnetic field, specifically including: An external magnetic field of -200mT to 200mT is applied to the spin terahertz transmitter, and the external magnetic field is rotated to reverse the magnetic moment direction of the ferromagnetic material layer in the spin terahertz transmitter. When the magnetic field angle of the external magnetic field is 0 ° Or 180 ° At that time, the terahertz waves emitted by the spin terahertz transmitter are linearly polarized; When the magnetic field angle of the external magnetic field is greater than 0 ° Less than 180 ° And not equal to 90 ° When, or when the magnetic field angle of the external magnetic field is greater than 180° ° Less than 360 ° And not equal to 270 ° At that time, the spin terahertz transmitter radiates obliquely elliptical polarized terahertz waves; When the magnetic field angle of the external magnetic field is equal to 90° ° Or 270 ° Furthermore, the picosecond charge flow J generated by the ferromagnetic / nonferromagnetic heterojunction c1 Picosecond charge flow J generated by antiferromagnetic / nonferromagnetic heterojunction c2 When they are not equal, the spin terahertz emitter radiates positively elliptically polarized radiation; the ferromagnetic / nonferromagnetic heterojunction is a heterojunction formed by a ferromagnetic material layer and a nonferromagnetic material layer; the antiferromagnetic / nonferromagnetic heterojunction is a heterojunction formed by an antiferromagnetic layer and a nonferromagnetic material layer. When the magnetic field angle of the external magnetic field is equal to 90° ° Or 270 ° Furthermore, the picosecond charge flow J generated by the ferromagnetic / nonferromagnetic heterojunction c1 Picosecond charge flow J generated by antiferromagnetic / nonferromagnetic heterojunction c2 When they are equal, the spin terahertz transmitter radiates circularly polarized terahertz waves; When the external magnetic field and the antiferromagnetic layer are at an angle to each other, and the external magnetic field rotates 180 degrees... ° Then, terahertz waves with opposite rotation directions are generated.

2. The chiral control method for a spin terahertz transmitter according to claim 1, characterized in that, The ferromagnetic material layer is made of two-dimensional ferromagnetic material or ferromagnetic metal; The non-ferromagnetic material layer is made of a topological material, which includes a topological insulator, a topological half-metal, or a heavy metal with a spin Hall angle greater than the Hall angle threshold.

3. The chiral control method for a spin terahertz transmitter according to claim 1, characterized in that, The spin terahertz emitter further includes: a substrate; The substrate is disposed below the ferromagnetic material layer or the antiferromagnetic layer.

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