Heterostructure of three-layer transition metal sulfide

Abstract

The invention relates to a three-layer transition metal sulfide heterostructure and a preparation method thereof, and the method comprises the steps: placing two layers of same two-dimensional transition metal sulfide in the outermost two layers, and placing a different two-dimensional transition metal sulfide in the middle, the two-dimensional transition metal sulfides on the outermost layers are rotated by theta / 2 and-theta / 2 respectively relative to the two-dimensional transition metal sulfide on the middle layer, so that the two-dimensional transition metal sulfides on the outermost layers are rotated by theta relatively, and a mirror surface torsion symmetrical three-layer corner TMD heterostructure of M01X2 / M02X2 / M01X2 is formed; the electron and hole layer separation of the interlayer excitons of the heterostructure enables the optical dipole moment to nearly disappear, so that the service life of the topological excitons is prolonged, and the conflict between the topological structure and the long service life is solved; the mirror torsional symmetry of the heterostructure provides an efficient Bose continuous medium model for interlayer Moire excitons, and quadrupole excitons with mirror symmetry and dipole excitons with opposite dipole moments can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum moiré superlattices, and particularly to a heterostructure of a three-layer transition metal sulfide. Background Art

[0002] Semiconductors based on two-dimensional transition metal dichalcogenides (TMDs) have become a platform for realizing strongly correlated electrons and topological non-triviality due to their narrow bandwidth and intertwined electron wave function characteristics. In TMD superlattices with non-trivial band topologies, many strongly correlated electron phenomena have been experimentally observed, such as Mott Insulators and Generalized Wigner Crystals; in TMD superlattices with topological bands, experimentally observed correlated phases with topological non-triviality, such as integer quantum anomalous Hall states and fractional quantum anomalous Hall states. The above experimental observations indicate that TMD moiré superlattices are a real material platform for fermionic quantum simulation.

[0003] The periodic characteristics of TMD superlattices enable exciton bands to obtain specific Chern numbers in an effective valley Zeeman field. Currently, incompressible correlated states of excitons and bosonic Mott insulators have been observed in TMD moiré superlattice heterobilayers, opening up new research fields for studying many-body states of bosons. In these superlattices, the modulation of moiré stripes causes excitons to be localized on a triangular lattice with significant on-site energy, effectively simulating the Bose-Hubbard model. For example, a research team found excitons with strong Hubbard interactions in a WSe / WS bilayer moiré superlattice. These excitons occupy the same moiré lattice position and exhibit correlated bosonic states similar to the electronic Mott insulating state.

[0004] However, in bilayer moiré superlattices, the relatively large optical dipole moment of in-layer excitons results in a short exciton lifetime. For this reason, some research has proposed adding a third layer of MoSe on the basis of a twisted homojunction tWSe 2 to form a three-layer TMD model of WSe 2 / WSe 2 / MoSe 2 2 to form interlayer excitons with a longer lifetime than in-layer excitons. However, this WSe 2 / WSe 2 2 / MoSe three-layer TMD model is not conducive to constructing a Hamiltonian for a continuous model. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a heterostructure of a three-layer transition metal sulfide.

[0006] A heterostructure of a three - layer transition metal sulfide, comprising:

[0007] A first two - dimensional transition metal sulfide layer M 01 X 2 stacked in sequence, a second two - dimensional transition metal sulfide layer M 02 X 2 and a third two - dimensional transition metal sulfide layer M 03 X 2 The first two - dimensional transition metal sulfide layer M 01 X 2 is rotated by θ / 2 relative to the second two - dimensional transition metal sulfide layer M 02 X 2 The third two - dimensional transition metal sulfide layer M 03 X 2 is rotated by -θ / 2 relative to the second two - dimensional transition metal sulfide layer M 02 X 2 and the first two - dimensional transition metal sulfide layer M 01 X 2 is the same as the third two - dimensional transition metal sulfide layer M 03 X 2 .

[0008] Furthermore, the first two - dimensional transition metal sulfide layer M 01 X 2 is rotated by θ relative to the third two - dimensional transition metal sulfide layer M 03 X 2 to form a two - dimensional transition metal sulfide with mirror - twist symmetry of M 01 X 2 / M 02 X 2 / M 03 X 2 .

[0009] Furthermore, the first two - dimensional transition metal sulfide layer M 01 X 2 , the second two - dimensional transition metal sulfide layer M 02 X 2 and the third two - dimensional transition metal sulfide layer M 03 X 2 are all single - layer.

[0010] Furthermore, the second two - dimensional transition metal sulfide layer M 02 X 2 is different from both the first two - dimensional transition metal sulfide layer M 01 X 2 and the third two - dimensional transition metal sulfide layer M 03 X 2 .

[0011] Further, the θ is 0.9° to 1.9°.

[0012] Further, M 01 、M 02 、M 03 is one of Ti, In, Ta, Mo, W, Re, and M 01 、M 03 is different from M 02 .

[0013] Further, X is S or Se.

[0014] Further, the first two-dimensional transition metal sulfide layer M 01 X 2 、the third two-dimensional transition metal sulfide layer M 03 X 2 is WSe 2 ; the second two-dimensional transition metal sulfide layer M 02 X 2 is MoSe 2 .

[0015] Compared with the prior art, the proposed three-layer twisted transition metal sulfide heterostructure of the present invention places two identical two-dimensional transition metal sulfides on the outermost two layers, places a different two-dimensional transition metal sulfide in the middle, and rotates the outermost two two-dimensional transition metal sulfides by θ / 2 and -θ / 2 relative to the two-dimensional transition metal sulfide in the middle layer, respectively, so that the outermost two two-dimensional transition metal sulfides rotate relative to each other by θ, forming a mirror-twisted symmetric M 01 X 2 / M 02 X 2 / M 01 X 2 three-layer twisted TMD heterostructure; the separation of electrons and hole layers of the interlayer excitons in this heterostructure makes the optical dipole moment nearly disappear, thereby increasing the lifetime of topological excitons and solving the conflict between the topological structure and the long lifetime; the mirror-twisted symmetry of this heterostructure ensures that the moiré potential energy generated by the moiré superlattice can be processed by harmonic approximation, thereby providing an efficient boson continuum model for the interlayer moiré excitons, that is, obtaining a continuous-type topological exciton energy band, and realizing quadrupole excitons with mirror symmetry and dipole excitons with opposite dipole moments. Long-lived excitons are beneficial to many application fields, especially the efficiency and stability of optoelectronic devices, directly affecting the development of new materials, the reliability of quantum information, and the improvement of the performance of optoelectronic systems.

[0016] Meanwhile, the present invention proposes a preparation method for a three-layer transition metal sulfide heterostructure, which is characterized by including the following steps:

[0017] S10 Attach a polymethyl methacrylate (PPC) film to the center of a polydimethylsiloxane (PDMS) pad on a glass slide to obtain a PDMS / PPC layer;

[0018] S20 Place monolayer M 01 X 2 , monolayer M 03 X 2 and monolayer M 02 X 2 at the center of the sample displacement stage of the microscope;

[0019] S30 Mount the PDMS / PPC layer on the glass slide to the cantilever of the microscope, and adjust the height of the microscope and the sample displacement stage. Locate monolayer M 01 X 2 in the eyepiece. Adjust the cantilever so that the lowest point of the PDMS / PPC layer aligns with monolayer M 01 X 2 , and slowly lower it until colored Newton's rings appear; Control the heating stage to heat, and observe the adhesion of PDMS / PPC and monolayer M 01 X 2 to obtain a PDMS / PPC / M 01 X 2 layer;

[0020] S40 Adjust the cantilever so that the lowest point of the PDMS / PPC / M 01 X 2 layer aligns with monolayer M 02 X 2 , and slowly lower it until colored Newton's rings appear; Control the heating stage to heat, and adjust the rotation angle of the platform to control the stacking angle between the PDMS / PPC / M 01 X 2 layer and monolayer M 02 X 2 . Observe the adhesion of the PDMS / PPC / M 01 X 2 layer and monolayer M 02 X 2 to obtain a PDMS / PPC / M 01 X 2 / M 02 X 2 layer;

[0021] S50 Adjust the cantilever so that the lowest point of the PDMS / PPC / M 01 X 2 / M 02 X 2 layer aligns with monolayer M 03 X 2, slowly decrease until the appearance of colored Newton's rings; control the heating of the heating stage and adjust the rotation angle of the stage to control the stacking angle of the PDMS / PPC / M 01 X 2 / M 02 X 2 layer and the single-layer M 03 X 2 ; observe the bonding of the PDMS / PPC / M 01 X 2 / M 02 X 2 layer and the single-layer M 03 X 2 through the CCD, and prepare the PDMS / PPC / M 01 X 2 / M 02 X 2 / M 03 X 2 layer;

[0022] S60 Adjust the cantilever to move along the positive half-axis direction of the Z-axis and remove the PDMS / PPC layer on the glass slide; remove the residual PPC of the M 01 X 2 / M 02 X 2 / M 03 X 2 layer by acetone immersion or annealing to prepare the three-layer M 01 X 2 / M 02 X 2 / M 03 X 2 heterojunction trench.

[0023] To better understand and implement the present invention, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the heterostructure of a WSe 2 / MoSe 2 / / WSe 2 of the present invention;

[0025] Figure 2 is Figure 1 a schematic diagram of exciton formation;

[0026] Figure 3 is a schematic diagram of the exciton Moiré energy band structure when the rotation angle is 1°;

[0027] Figure 4 is the Berry curvature diagram of the lowest exciton energy band when the Chern number is -1;

[0028] Figure 5 The real-space distribution map of the bottom layer component of Wannier A;

[0029] Figure 6 The real-space distribution map of the top layer component of Wannier A;

[0030] Figure 7 The real-space distribution map of the bottom layer component of Wannier B;

[0031] Figure 8 The real-space distribution map of the top layer component of Wannier B;

[0032] Figure 9 The real-space distribution map of the bottom layer component of Wannier O;

[0033] Figure 10 The real-space distribution map of the top layer component of Wannier O;

[0034] Figure 11 The ground state diagrams of sites A, B, and O when the filling number is 1 / 3;

[0035] Figure 12 The ground state diagrams of sites A, B, and O when the filling number is 1. Detailed implementation manners

[0036] Please refer to Figure 1 and Figure 2 The heterostructure of the three-layer transition metal sulfide according to the present invention includes a first two-dimensional transition metal sulfide layer M 01 X 2 , a second two-dimensional transition metal sulfide layer M 02 X 2 and a third two-dimensional transition metal sulfide layer M 03 X 2 , wherein the first two-dimensional transition metal sulfide layer M 01 X 2 is rotated by θ / 2 relative to the second two-dimensional transition metal sulfide layer M 02 X 2 , and the third two-dimensional transition metal sulfide layer M 03 X 2 is rotated by -θ / 2 relative to the second two-dimensional transition metal sulfide layer M 02 X 2 so that the first two-dimensional transition metal sulfide layer M 01 X 2 is rotated by θ relative to the third two-dimensional transition metal sulfide layer M 03 X 2 to form a mirror-twist symmetric M 01 X 2 / M 02 X2 / M 03 X 2 of two-dimensional transition metal sulfide.

[0037] Among them, the first two-dimensional transition metal sulfide layer M 01 X 2 , the second two-dimensional transition metal sulfide layer M 02 X 2 and the third two-dimensional transition metal sulfide layer M 03 X 2 are all single layers; the first two-dimensional transition metal sulfide layer M 01 X 2 is the same as the third two-dimensional transition metal sulfide layer M 03 X 2 , and the second two-dimensional transition metal sulfide layer M 02 X 2 is different from the first two-dimensional transition metal sulfide layer M 01 X 2 and the third two-dimensional transition metal sulfide layer M 03 X 2 .

[0038] Among them, M 01 , M 02 , M 03 is one of Ti, In, Ta, Mo, W, Re, and M 01 and M 03 are the same, M 01 , M 03 are different from M 02 ; X is S or Se.

[0039] At the same time, set θ to 0.9° - 1.9°.

[0040] At the same time, the present invention provides a preparation method for the heterostructure of the three-layer transition metal sulfide, including the following steps.

[0041] S10 Stick a polymethyl methacrylate (PPC) film to the center of a polydimethylsiloxane (PDMS) pad on a glass slide to obtain a PDMS / PPC layer.

[0042] S20 Place a single layer of M 01 X 2 , a single layer of M 03 X 2 and a single layer of M 02 X 2 at the center of the sample displacement stage of a microscope.

[0043] S30 Mount the PDMS / PPC layer on the glass slide to the cantilever of the microscope, and adjust the height of the microscope and the sample displacement stage to find a single layer of M in the eyepiece01 X 2 , adjust the cantilever to align the lowest point of the PDMS / PPC layer with monolayer M 01 X 2 , slowly lower it until colored Newton's rings appear; control the heating stage to heat, and observe the bonding of PDMS / PPC and monolayer M through the CCD 01 X 2 to obtain the PDMS / PPC / M 01 X 2 layer.

[0044] S40 Adjust the cantilever to align the lowest point of the PDMS / PPC / M 01 X 2 layer with monolayer M 02 X 2 , slowly lower it until colored Newton's rings appear; control the heating stage to heat, and adjust the rotation angle of the platform to control the stacking angle between the PDMS / PPC / M 01 X 2 layer and monolayer M 02 X 2 , observe the bonding of PDMS / PPC / M 01 X 2 layer and monolayer M 02 X 2 to obtain the PDMS / PPC / M 01 X 2 / M 02 X 2 layer.

[0045] S50 Adjust the cantilever to align the lowest point of the PDMS / PPC / M 01 X 2 / M 02 X 2 layer with monolayer M 03 X 2 , slowly lower it until colored Newton's rings appear; control the heating stage to heat, and adjust the rotation angle of the platform to control the stacking angle between the PDMS / PPC / M 01 X 2 / M 02 X 2 layer and monolayer M 03 X 2 , observe the bonding of PDMS / PPC / M 01 X 2 / M 02 X 2 layer and monolayer M 03 X 2 to obtain the PDMS / PPC / M 01 X 2 / M 02 X2 / M 03 X 2 layer.

[0046] S60 adjusts the cantilever to move along the positive half-axis direction of the Z-axis to remove the PDMS / PPC layer on the glass slide; the residual PPC of the M 01 X 2 / M 02 X 2 / M 03 X 2 layer is removed by acetone immersion or annealing to obtain a three-layer M 01 X 2 / M 02 X 2 / M 03 X 2 heterojunction trench.

[0047] In specific implementation, the first two-dimensional transition metal sulfide layer M 01 X 2 , the third two-dimensional transition metal sulfide layer M 03 X 2 is WSe 2 , the second two-dimensional transition metal sulfide layer M 02 X 2 is MoSe 2 , forming a three-layer twisted TMD heterostructure of WSe 2 / MoSe 2 / WSe 2 , and the preparation method is as follows:

[0048] S10 uses a tape with small holes to pick up the polymethyl methacrylate (PPC) film spin-coated on the silicon wafer, and pastes the PPC film at the center of the polydimethylsiloxane (PDMS) pad on the glass slide to obtain the PDMS / PPC layer.

[0049] S20 places two single-layer WSe 2 and single-layer MoSe 2 at the center of the sample displacement stage of the microscope.

[0050] S30 installs the PDMS / PPC layer on the glass slide at the cantilever of the microscope, and adjusts the height of the microscope and the sample displacement stage. Find a single-layer WSe 2 area in the eyepiece, adjust the cantilever so that the lowest point of the PDMS / PPC layer aligns with this single-layer WSe 2 area, and slowly lower it until colored Newton's rings appear; control the temperature of the heating stage to 40°C, heat for 10 minutes when it reaches 40°C, and observe the bonding of PDMS / PPC and single-layer WSe 2 through the CCD to obtain PDMS / PPC / WSe 2Layer.

[0051] Furthermore, make WSe 2 The single-layer region is located at the edge of the Newton's rings.

[0052] S40 adjusts the cantilever to align the lowest point of the PDMS / PPC / WSe 2 layer with the single-layer MoSe 2 region, slowly lower it until colored Newton's rings appear; control the temperature of the heating stage to increase by 10 °C as a superposition unit in turn until it reaches 110 °C, after reaching 110 °C, heat for 10 min, adjust the rotation angle of the platform to control the PDMS / PPC / WSe 2 layer and the single-layer MoSe 2 stacking angle, observe the PDMS / PPC / WSe through the CCD 2 layer and the single-layer MoSe 2 adhesion, and prepare the PDMS / PPC / WSe 2 / MoSe 2 layer.

[0053] S50 adjusts the cantilever to align the lowest point of the PDMS / PPC / WSe 2 / MoSe 2 layer with another single-layer WSe 2 region, slowly lower it until colored Newton's rings appear; control the temperature of the heating stage to remain at 110 °C, adjust the rotation angle of the platform to control the PDMS / PPC / WSe 2 / MoSe 2 layer and the single-layer WSe 2 stacking angle, observe the PDMS / PPC / WSe through the CCD 2 / MoSe 2 layer and the single-layer WSe 2 adhesion, and prepare the PDMS / PPC / WSe 2 / MoSe 2 / WSe 2 layer.

[0054] S60 adjusts the cantilever to move along the positive half-axis direction of the Z-axis, and remove the PDMS / PPC layer on the glass slide; remove the residual PPC of the WSe 2 / MoSe 2 / WSe 2 layer by annealing, and prepare the three-layer WSe 2 / MoSe 2 / WSe 2 heterojunction trench, where keep a low-pressure state during annealing, the gas introduced is 300 sccm Ar, the annealing temperature is 290 °C, and the time is 8 h.

[0055] The physical mechanism of the present invention is analyzed as follows.

[0056] (1) Obtaining excitonic topological energy bands

[0057] Since the exciton binding energy (about 100 meV) is much larger than the moiré potential and the interlayer hybridization potential (0 - 10 meV), the excitons in the moiré superlattice are approximated, and the physical effects brought by the moiré superlattice are ignored, and the Bethe - Salpeter equation (BXE) is solved.

[0058] The exciton state is described by the center - of - mass momentum, and the corresponding exciton wave function |X l (Q)> satisfies:

[0059]

[0060] where: |0> is the vacuum state with the valence band filled with electrons, A is the normalization coefficient, represents generating an electron in the conduction band of the +K valley in the MoSe 2 layer, represents generating a hole in the valence band of the +K valley in the top - layer WSe 2 layer, τ = ±1 refers to the ±K valleys, k is the relative momentum of the electron - hole pair, Q is the center - of - mass momentum of the electron - hole pair, where, is the effective mass of the exciton, is the relative - motion wave function of the electron - hole pair in momentum space, is normalized <X l (Q)|X l (Q)> = 1.

[0061] |X l (Q)> with 1 referring to the exciton wave function of the top - layer WSe 2 layer. Similarly, the exciton wave function |X 2 of the bottom - layer WSe 2 (Q)> satisfies:

[0062]

[0063] where: represents generating a hole in the valence band of the +K valley in the bottom - layer WSe 2 layer.

[0064] The electron and hole in an exciton are bound by the Coulomb interaction. In the parabolic - band approximation, when the binding energy is small compared to the band gap, the parabolic approximation is accurate. At this time, the relative wave function of the electron - hole pair is determined by the following formula:

[0065]

[0066] where: and are the conduction band dispersion and valence band dispersion of the monolayer under the effective mass approximation, E g is the band gap, S is the exciton energy band index, is the direct interlayer Coulomb interaction matrix, A is the normalization coefficient, ε = 3.8 is the effective dielectric constant, and d = 0.67 nm is the interlayer distance.

[0067] For MoSe 2 , For WSe 2 , Substitute the above parameters into the BXE equation and solve it to obtain the exciton energy E b,X = 161 meV.

[0068] According to the calculated exciton internal wave function used to construct the exciton moiré Hamiltonian.

[0069] Considering the moiré potential of the moiré superlattice and the influence of interlayer hybridization, the Hamiltonian of the interlayer exciton continuous model is derived.

[0070] Since the valence band is located in the tWSe 2 superlattice, the hole component of the exciton will experience moiré potential modulation. The form of the moiré potential:

[0071]

[0072] where: V and Φ are the amplitude and phase parameters of the moiré potential, s i,l = (-1) i+l-1 , and are the moiré reciprocal lattice vectors, is the counterclockwise rotation around the z-axis by

[0073] Project U l (r) onto the moiré potential through Fourier transform, and we obtain the moiré potential of the exciton:

[0074]

[0075] where: “+” represents considering the +K valley, and “-” reflects that the exciton experiences a moiré potential opposite to that of the valence electrons, depends on the overlap between the exciton internal wave function and the relative displacement α c g 1 and decreases with the increase of the twist angle.

[0076] Since there is real-space periodic interlayer hybridization between the holes in the valence band of tWSe 2 , X 1 and X2 Exciton hybridization leads to non-trivial layer pseudospin winding. In the lowest-order harmonic approximation, the interlayer hybridization potential of the +K valley is expressed as:

[0077]

[0078] where: t is the interlayer tunneling strength, q 1 = K 1 -K 2 is the momentum offset of the K point in the two layers of WSe 2 , and can be obtained by triple rotation of q 1 . By projecting onto the exciton vector, the interlayer hybridization potential of the +K valley can be obtained:

[0079]

[0080] Combining the above equations, the complete exciton moiré Hamiltonian with {|X 1 > + ,|X 2 > +} as the basis vectors is obtained:

[0081]

[0082] Please refer to Figure 3 , and the parameters used are (V, Φ) = (7.8 meV, 65.7°), t = 2 meV. Expand the Hamiltonian of this continuous model by plane waves and diagonalize it to obtain the exciton moiré band diagram at a twist angle of 1°. The band structure has three narrow low-energy bands isolated from the high-energy bands.

[0083] Please refer to Figure 4 , the Berry curvature of the lowest energy band shows a strong amplitude at the high-symmetry points γ and κ and a band inversion occurs at the high-symmetry points. Due to the hybridization between the X 1 and X 2 excitons, an energy gap is opened between the two lowest energy bands, and the Chern number combination of the two lowest energy bands is (-1, 1), indicating the presence of a pair of time-reversal symmetry-protected bosonic helical edge states in the gap.

[0084] (II) Construction of Wannier functions

[0085] Since the topological Chern number combination of the three lowest exciton moiré bands is 0, Wannier states are constructed for the three lowest exciton moiré bands at θ = 1°. The Wannier function (+K valley) at R = 0 is expressed as:

[0086]

[0087] where τ is the valley index, n are three Wannier orbits, N is the number of k points in the first Brillouin zone, is the Bloch-like state related to the Wannier state, is the Bloch state of the n-th moiré band at the k point, V kτ is fixed gauge unitary matrix, which can maximize polarization to the top layer and in real space is real,

[0088] polarization to the bottom layer and in real space is real, in real space O=(0,0)a M .

[0089] Please refer to Figures 5 to 8 , the Wannier function with θ = 1° was constructed using the above method, and W A , W B , W O The top and bottom components of the three were plotted. W A and W B are dominated by the bottom and top components respectively, indicating that the A and B sites in real space are interlayer excitons with downward and upward dipole moments respectively, and are mutually converted by operations plus lattice translation.

[0090] Please refer to Figure 9 , Figure 10 , W O has significant and equal weights on both layers, indicating that the O site is a quadrupole exciton composed of holes provided by the top and bottom layers respectively, and one electron provided by the middle layer, and satisfies symmetry.

[0091] (III) Constructing the tight-binding (TB) Hamiltonian to calculate the quantum many-body phase diagram

[0092] Based on the above results, an effective Hamiltonian of the Bose tight-binding model for the honeycomb lattice formed by W A , W B , W o orbits was constructed:

[0093]

[0094] where: is the boson creation (annihilation) operator acting on the function, the real-space nearest-neighbor vector and nearest-neighbor vector Hopping parameter E n″ (k) is the energy of the n-th moiré band in the +K valley, Together with constitute the Kane - Mele model. The dispersion of the effective KM model is in good agreement with the energy band structure of the continuous model, indicating the successful construction of the TB Hamiltonian model.

[0095] Considering the on-site R i The exciton interaction U is the on-site energy given by the following formula:

[0096]

[0097] where: α refers to the three lattice points A, B, and O,

[0098] Considering two sites R i and R j The Coulomb interaction U between the excitons is given by the following formula:

[0099]

[0100] where: α and β refer to the three lattice points A, B, and O, R i ≠R j , when α = β, calculate the next-nearest neighbor interaction between the same lattice points, and the same as above; when α ≠ β, calculate the nearest neighbor interaction between different lattice points d represents the layer spacing, ε r represents the relative dielectric constant.

[0102] Based on the three - orbital model, the many - body Hamiltonian considering the exciton Coulomb interaction can be expressed as:

[0103]

[0104] where: is the corresponding particle number operator, <i, j> represents the next - nearest neighbor lattice sites, and <<i, j>> represents the nearest neighbor lattice sites.

[0105] By calculating its ground state through the boson Gutzwiller variational method to study the quantum many - body phase of the three - layer twisted TMD superlattice, the variational ground - state wave function can be expressed in the following form:

[0106]

[0107] where: α are the three Wannier orbits of A, B, and O, N αis the total number of lattice sites related to W α The local wave function of W at site i is α where are variational parameters, and |n> iα represents the corresponding occupation number state.

[0108] Substituting the above variational wave function into the many-body Hamiltonian, the energy expression can be obtained:

[0109]

[0110] In the process of finding the minimum, the global energy minimum is obtained with different initial states.

[0111] Please refer to Figure 11 , where the case of filling number is plotted. For θ i = 0.9°, θ f = 1.9°, the order parameters φ iα = <b iα > of the three types of lattice points A, B, and O are all non-zero. When the filling number is , the weak exciton interaction leads to the emergence of superfluid characteristics.

[0112] Please refer to Figure 12 , where the case of filling number 1 is plotted. The order parameters φ iα = <b iα > of the three types of lattice points A, B, and O are all equal to 0, and the average particle number <n iα > are all equal to 1. The ratio of the nearest-neighbor hopping parameter t to the on-site energy U in the small rotation angle range is much less than 1, resulting in the three types of lattice points A, B, and O showing the characteristics of a Mott insulator.

[0113] Comparing the two plotted quantum many-body phase diagrams, it is obvious to notice the strong physical effects brought about by the difference in filling number.

[0114] The heterostructure of the three-layer twisted transition metal sulfide proposed by the present invention is formed by placing two identical two-dimensional transition metal sulfides on the outermost two layers, placing a different two-dimensional transition metal sulfide in the middle, and rotating the two outermost two-dimensional transition metal sulfides by θ / 2 and -θ / 2 respectively relative to the two-dimensional transition metal sulfide in the middle layer, so that the two outermost two-dimensional transition metal sulfides are rotated relative to each other by θ, forming a mirror-twisted symmetric M 01 X 2 / M 02 X 2 / M 01 X 2Three-layer twisted TMD heterostructure; the electron and hole layer separation of the interlayer excitons in this heterostructure makes the optical dipole moment nearly disappear, thereby increasing the lifetime of topological excitons and solving the conflict between the topological structure and long lifetime; the mirror-twist symmetry of this heterostructure ensures that the moiré potential energy generated by the moiré superlattice can be treated by harmonic approximation, thereby providing an efficient boson continuum model for interlayer moiré excitons, that is, obtaining a continuous-type topological exciton energy band, and enabling the realization of quadrupolar excitons with mirror symmetry and dipolar excitons with opposite dipole moments. Long-lived excitons are beneficial to many application fields, especially the efficiency and stability of optoelectronic devices, which directly affect the development of new materials, the reliability of quantum information, and the improvement of optoelectronic system performance.

[0115] On the other hand, the valley-projected exciton energy band structure of the heterostructure of three-layer twisted transition metal sulfides proposed in the present invention has a set of rich boson topological bands, and these topological bands have opposite Chern numbers with opposite valley pseudospins, indicating the existence of a pair of time-reversal symmetry-protected boson helical edge states in the energy gap. Due to the spin-momentum locking and topology of the boson helical edge states, they can be used for the technical development of quantum computing and information transmission and more stable electron and information processing in nanoscale electronic devices.

[0116] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, "a plurality" and "several" refer to two or more; "and / or" means any or all possible combinations including one or more of the associated listed items; "first", "second", "third", etc. are only used for distinction and not for describing a specific order or sequence, nor can they be understood as indicating or implying relative importance. When the above description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0117] The embodiments described above only represent some embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the scope included in the present invention.

Claims

1. A three-layer transition metal sulfide heterostructure comprising: The first two-dimensional transition metal sulfide layers M are stacked sequentially 01 X2, second two-dimensional transition metal sulfide layer M 02 X2 and the third two-dimensional transition metal sulfide layer M 03 X2, characterized in that the first two-dimensional transition metal sulfide layer M 01 X2 is relative to the second two-dimensional transition metal sulfide layer M 02 X2 rotates by θ / 2, the third two-dimensional transition metal sulfide layer M 03 X2 is relative to the second two-dimensional transition metal sulfide layer M 02 X2 rotates -θ / 2, and the first two-dimensional transition metal sulfide layer M 01 X2 and the third two-dimensional transition metal sulfide layer M 03 Same as X2.

2. The three-layer transition metal sulfide heterostructure according to claim 1, characterized in that: The first two-dimensional transition metal sulfide layer M 01 X2 relative to the third two-dimensional transition metal sulfide layer M 03 X2 rotates by θ to form a mirror-twist symmetric M 01 X2 / M 02 X2 / M 03 Two-dimensional transition metal sulfides of X2.

3. The three-layer transition metal sulfide heterostructure according to claim 2, characterized in that: The first two-dimensional transition metal sulfide layer M 01 X2, second two-dimensional transition metal sulfide layer M 02 X2 and the third two-dimensional transition metal sulfide layer M 03 X2 are all single-layer.

4. The three-layer transition metal sulfide heterostructure according to claim 2, characterized in that: The second two-dimensional transition metal sulfide layer M 02 X2 and the first two-dimensional transition metal sulfide layer M 01 X2, third two-dimensional transition metal sulfide layer M 03 X2 is different.

5. The three-layer transition metal sulfide heterostructure according to any one of claims 2 to 4, characterized in that: The θ is 0.9° to 1.9°.

6. The three-layer transition metal sulfide heterostructure according to claim 5, characterized in that: M 01 、M 02 、M 03 It is one of Ti, In, Ta, Mo, W, and Re. 01 、M 03 With M 02 Not the same.

7. The three-layer transition metal sulfide heterostructure according to claim 6, characterized in that: X is S or Se.

8. The three-layer transition metal sulfide heterostructure according to claim 7, characterized in that: The first two-dimensional transition metal sulfide layer M 01 X2, third two-dimensional transition metal sulfide layer M 03 X2 is WSe2; the second two-dimensional transition metal sulfide layer M 02 X2 is MoSe2.

9. A method for preparing a three-layer transition metal sulfide heterostructure, characterized in that: The following steps are involved: S10: a polymethyl methacrylate (PPC) film is attached to the center of a polydimethylsiloxane (PDMS) pad on a glass slide to prepare a PDMS / PPC layer; S20 will be a single-layer M 01 X2, single layer M 03 X2 and single-layer M 02 X2 is placed at the center of the sample translation stage of the microscope; S30 Install the PDMS / PPC layer on the glass slide to the cantilever of the microscope, adjust the microscope height and sample displacement stage, and find the single layer M in the eyepiece. 01 X2, adjust the cantilever so that the lowest point of the PDMS / PPC layer is aligned with the single layer M 01 X2, slowly descend until the colored Newton rings appear; control the heating stage to heat, and observe the PDMS / PPC and the single layer M through CCD 01 X2 bonding to obtain PDMS / PPC / M 01 X2 layer; S40 adjusts the cantilever to make PDMS / PPC / M 01 The lowest point of the X2 layer is aligned with the single layer M 02 X2, slowly descend until the colored Newton rings appear; control the heating stage to heat, and adjust the platform rotation angle to control PDMS / PPC / M 01 X2 layer and single layer M 02 Stacking angle of X2, PDMS / PPC / M observed by CCD 01 X2 layer and single layer M 02 X2 bonding to obtain PDMS / PPC / M 01 X2 / M 02 X2 layer; S50 adjusts the cantilever to make PDMS / PPC / M 01 X2 / M 02 The lowest point of the X2 layer is aligned with the single layer M 03 X2, slowly descend until the colored Newton rings appear; control the heating stage to heat, and adjust the platform rotation angle to control PDMS / PPC / M 01 X2 / M 02 X2 layer and single layer M 03 Stacking angle of X2, PDMS / PPC / M observed by CCD 01 X2 / M 02 X2 layer and single layer M 03 X2 bonding to obtain PDMS / PPC / M 01 X2 / M 02 X2 / M 03 X2 layer; S60 adjusts the cantilever to move along the positive semi-axis direction of the Z axis to remove the PDMS / PPC layer on the glass slide; M 01 X2 / M 02 X2 / M 03 The residual PPC of X2 layer is removed to obtain three layers of M 01 X2 / M 02 X2 / M 03 X2 heterojunction trench.

10. The method for preparing a three-layer transition metal sulfide heterostructure according to claim 9, characterized in that: The residual PPC was removed by annealing. The low pressure was maintained during annealing. 300 sccm of Ar was introduced. The annealing temperature was 290°C and the annealing time was 8 h.

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