Cascade quantum well structure based on regional conductivity difference and coherent coupling control method

Abstract

The invention relates to the technical field of quantum, and particularly discloses a cascade quantum well structure based on regional conductivity difference and a coherent coupling control method.The cascade quantum well structure is characterized in that a single-layer MoS2 nanobelt is used as a substrate, zigzag edges and armchair edges are alternately arranged in the length direction of the nanobelt, the zigzag edges are quantum well regions, and the armchair edges are arranged in the quantum well regions; the handrail type edge is a barrier region, and a well-barrier periodic structure is formed. According to the invention, the conductivity of different regions is spatially modulated to form a barrier region and a well region, so that a multi-well cascaded quantum structure is constructed; coherent coupling control and energy level controllable distribution of quantum states are realized by utilizing combined regulation and control of structural geometric parameters (quantum well width and barrier width) and an external electric field. External heterogeneous stacking or chemical modification is not needed, construction and adjustment of the coherent state are achieved only by adjusting the geometric structure of the material, and the method is suitable for design of integratable and high-stability quantum devices.

Description

Technical Field

[0001] This invention relates to the field of quantum technology, specifically to a cascaded quantum well structure based on regional conductivity differences and a coherent coupling control method. Background Technology

[0002] Coherent coupling between discrete quantum states in cascaded quantum wells is a core physical mechanism for many mesoscopic transport phenomena. This process enables the electron wavefunctions to interact in a controllable manner, thus providing diverse transport characteristics and manipulation techniques for quantum devices. In recent years, research on coherent coupling in multiple quantum wells has been widely used in the construction of molecular-like quantum devices and the construction of energy-selective filtering structures, especially providing a feasible path for the realization and manipulation of qubits. Coherent coupling between multiple quantum wells not only supports the functionalization of devices but also directly promotes the development of high-fidelity quantum computing.

[0003] Recent theoretical and experimental results demonstrate that band structure manipulation in nanoribbon structures offers new insights into achieving robust coherent coupling. For example, confinement effects significantly influence exchange interactions in dilute magnetic semiconductor quantum well nanoribbons, while interlayer hybridization enhances thermoelectric properties in twisted bilayer blue phosphorus nanoribbons. However, traditional methods largely rely on multi-material heterostructure stacking or chemical modification. For instance, graphene nanoribbons often require additional modifications or precursor chemical pathways to form stable coupled states. This can be achieved by introducing nanodots or anchoring groups at the edges to construct heterojunctions for narrowband photoemission, or by using substrate and interface effects to stabilize coherent electronic states and amplify coupling. This dependence on external modifications and interfaces increases the difficulty of structural realization and weakens stability in quantum computing due to interface scattering, limiting scalability and on-chip integration performance.

[0004] Therefore, there is an urgent need for a new design approach that can naturally form cascaded quantum well structures within a single two-dimensional semiconductor material based on regional conductivity differences, and achieve coherent coupling and programmable control through geometric parameters and an applied electric field, in order to realize highly stable, integrable, and multifunctional quantum devices. Summary of the Invention

[0005] To address the aforementioned problems, this invention presents a cascaded quantum well structure and coherent coupling control method based on regional conductivity differences. In a single two-dimensional semiconductor material, spatial modulation of the conductivity in different regions creates barrier and well regions, thereby constructing a multi-well cascaded quantum structure. By jointly controlling the structural geometric parameters (quantum well width, barrier width) and an applied electric field, coherent coupling control of the quantum states and controllable energy level distribution are achieved. No external heterostructure stacking or chemical modification is required; the construction and regulation of coherent states are achieved solely by adjusting the material's geometry, making it suitable for the design of integrable, highly stable quantum devices.

[0006] The technical solution of this invention is a cascaded quantum well structure based on regional conductivity differences, comprising the following steps: S1. Using a single-layer MoS2 nanoribbon as the structural substrate, zigzag edges and armchair edges are alternately arranged along the length of the nanoribbon. The zigzag edges are quantum well regions, and the armchair edges are potential barrier regions, forming a well-barrier unit (zigzag edge - armchair edge). S2, Define the well width With the width of the barrier zone Geometric parameters; S3. Based on the number of well-barrier units and geometric parameters of the target cascaded quantum well structure, the well-barrier units in S1 are continuously transitioned along the edge direction of the nanoribbon to obtain the cascaded quantum well structure.

[0007] Furthermore, the nanoribbon width maintains a distance of more than 2 nm between its upper and lower boundaries.

[0008] Furthermore, in S1, the serrated edge and the armrest edge are perpendicularly connected and alternately arranged.

[0009] Furthermore, the width of each well region in S2 The width of each barrier region is 3 nm to 6 nm. same.

[0010] Furthermore, the number of periods of the well-barrier units in the cascaded quantum well is 3 to 15.

[0011] This invention also relates to a coherent coupling control method for the aforementioned cascaded quantum well structure, comprising the following: 1) Change the sink width Or the barrier is wide Among them, regulation Achieve continuous switching between strong and weak coupling, and adjust Achieving energy level matching and anti-crossover control through rational design and The combination of these elements enables precise control over the energy level spacing and wavefunction reconstruction in multi-well systems. 2) Electrodes are set at both ends of the cascaded quantum well structure, and a horizontal electric field is applied to the structure to initially adjust the energy level detuning between the wells and realize coherent coupling based on spatial symmetry. Then, a vertical electric field is applied to the cascaded quantum well structure to precisely control the energy level position and coherent coupling strength between the wells. 3) In the above control steps, the transfer coefficient spectrum with an energy range of (-0.5 eV to 0.1 eV) is calculated. When energy level splitting, anti-crossover characteristics, or symmetric selective mixing are observed, it indicates that the system has entered the controllable coherent coupling region. Based on the test results, the energy range in which coherent coupling occurs is determined. , The applied electric field is fed back to correct the state and lock in a stable coherent state, thus achieving coherent coupling control of the cascaded quantum well structure.

[0012] Further, in step 2), the vertical electric field is a local electric field and / or a global electric field; applying a local electric field involves placing a local gate above or below one or more quantum well regions and applying the local electric field. or gate voltage When the local electric field causes two symmetry-matched energy levels to approach each other, an anti-crossing characteristic appears in the system, the wave function is reorganized and mixed, and coherent state switching is achieved, enabling precise addressing of specific quantum channels; when a global electric field is applied, an electric field is applied to the entire system. or gate voltage It is used for overall energy level shifting and system energy level equilibrium, achieving continuous adjustment while maintaining quantum state coherence.

[0013] Furthermore, in step 2), the local electric field is used for the fine selection and dynamic switching of specific energy levels, while the global electric field is used for the coordinated translation and initial registration of the overall energy band. The combination of the two can realize a two-layer electric control mode of "coarse adjustment first, then fine adjustment".

[0014] Furthermore, in step 3) [ , Within -0.5eV to 0.1eV.

[0015] This invention also relates to the application of the cascaded quantum well structure based on regional conductivity differences or the control method described herein in on-chip quantum state modulation, logic qubit construction, and / or tunable bandgap structure design.

[0016] The present invention has the following beneficial effects: This invention constructs a multi-quantum-well structure based on a single molybdenum disulfide (MoS2) material. It fully utilizes the natural conductivity difference between the handrail-shaped and sawtooth-shaped edges to achieve spatial partitioning of the potential barrier and quantum wells. It eliminates the need for heterojunctions or complex interfaces, avoiding the problems of lattice mismatch and interface state interference in traditional heterostructures, and significantly improving the stability and consistency of the device.

[0017] This invention enables coherent control and energy level alignment of the electronic wavefunction across multiple wells by synergistically adjusting the well width, barrier width, and applied electric field parameters (local or global). This allows for precise adjustment of the coherent switching, coupling strength, and energy level matching of quantum states, exhibiting excellent physical controllability and engineering feasibility.

[0018] The technical solution of this invention adopts the idea of ​​combining geometric partitioning design with electric field control. The structure realization does not rely on complex epitaxial processes. It can be realized by edge engineering and electrode placement in a single-layer MoS2 nanoribbon. It is directly compatible with traditional planar electronic device processes and has high integration potential. The coherent coupling mechanism of this cascaded quantum well can be applied to on-chip quantum state modulation, logical qubit construction and tunable band structure design, providing a new way for development in two-dimensional material systems and having the universality to be extended to other transition metal sulfides. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the three-level coupled quantum well structure of MoS2 nanoribbons used in Example 1. The diagram shows three coupled quantum well regions formed by alternating sawtooth (metallic) and armrest (semiconductor) regions along the edge direction. , , and its corresponding barrier ~ .

[0020] Figure 2 This is a schematic diagram of the full structure of serrated and handrail-shaped MoS2 nanoribbons, showing the alternating connection of the two edge structures.

[0021] Figure 3 This diagram illustrates the band alignment relationship between sawtooth and armrest-shaped MoS2 nanoribbons, indicating conduction band offset. Price band offset This indicates that the band difference between the quantum well region and the barrier region forms the condition for well state localization.

[0022] Figure 4 The hole transport spectrum shows the energy level distribution and discrete peak structure of the multi-well system under zero external field.

[0023] Figure 5 This is an electron transport spectrum, showing the distribution and coupling relationships of bound states in energy space.

[0024] Figure 6 for The spatial probability distribution diagram of the state shows that the wave function expands continuously in the three quantum well intervals, which is a characteristic of strongly coupled state.

[0025] Figure 7 for The spatial probability distribution diagram of the state shows that the wave function is mainly localized in the two quantum wells, and the distribution in the central well is weak, which is a characteristic of weakly coupled state.

[0026] Figure 8 For different barrier widths The electron transport spectrum comparison diagram below shows the trend of coupling strength as geometric parameters change.

[0027] Figure 9 For different barrier widths The hole transport spectrum comparison diagram below illustrates the variation of energy level splitting with barrier thickness.

[0028] Figure 10 for The local magnified transmission spectrum at 12.1 nm shows a weak splitting peak, confirming that the system still maintains limited coupling.

[0029] Figure 11 For different central sink widths The electron transport spectrum under the given conditions shows the locations where energy levels approach each other and where anti-crossing occurs.

[0030] Figure 12 For different central sink widths Hole transport spectrum under certain conditions reflects the influence of geometric modulation on coherent coupling.

[0031] Figure 13 For local electric field The diagram showing the changes in the electron transport spectrum under the influence of the electric field strength illustrates the relationship between energy level shifts and anti-crossover characteristics.

[0032] Figure 14 For local electric field The hole transport spectrum changes under the influence of the action, correspondingly showing the enhanced coupling and coherent switching behavior.

[0033] Figure 15 For the global electric field The electron transport spectrum changes under the influence of the action, showing the linear shift and parallel slope characteristics of the entire band.

[0034] Figure 16 For the global electric field The hole transport spectrum changes under the influence of the action show that the energy levels shifted as a whole and no local anti-crossing phenomenon occurred. Detailed Implementation

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.

[0036] Example 1: like Figure 1As shown, this embodiment utilizes the cascaded quantum well construction method proposed in this invention to realize a three-level coupled quantum well (TCQW) structure in a monolayer MoS2 nanoribbon. To quantitatively analyze the electron transport behavior of this structure, calculations were performed using the kwant software platform combined with a six-band tight-binding model. The system alternately incorporates serrated (metallic) and armrest-shaped (semiconductor) edge segments along the same edge direction, with the serrated portion constituting the quantum well region. , , The armrest-shaped section forms a barrier zone. ~ .

[0037] like Figure 2 As shown, there are significant differences in the band structure characteristics of serrated and armrest-shaped MoS2 nanoribbons. The band gap contrast and band alignment relationship between the two edge types are as follows: Figure 3 As shown. Its conduction band offset 0.28 eV, valence band offset 0.55 eV. This band difference causes the charge carriers to be localized within the sawtooth region, thus spontaneously forming three couplerable quantum wells in our system.

[0038] In this embodiment, the three-level coupled quantum well structure has five serrated edges, with the first serrated edge handling electron input and the fifth handling electron collection. The nanoribbon width is approximately 8 nm; L1 and L2 serve as the front and rear ends of the cascaded quantum wells, ranging from 2 nm to 4 nm; Lw1, Lwc, and Lw3 are the widths of the three quantum wells in the cascaded quantum wells, with no clear size relationship between them, ranging from 3 nm to 6 nm; in this embodiment, the width of each well... 3.0nm, barrier width approximately 2.2nm = 3.0 nm. In the absence of an external electric field, since the potential barrier has a finite height and width, charge carriers can couple between the wells through quantum tunneling to form a cluster of energy levels with long-range coherent characteristics. The wave function is continuously distributed along the edge of the nanoribbon. The calculation results below will directly prove the existence of this coherent coupling feature in this system.

[0039] Based on the 6-band tight-binding model, the carrier transport characteristics of this system are solved using the non-equilibrium Green's function (NEGF) method. The electron-hole transport spectrum of this system is as follows: Figure 4 and Figure 5 As shown, a series of discrete peaks appear in the transmission spectrum, indicating that bound quantum states do indeed exist in the sawtooth edge region. To further verify the coherent coupling between these quantum states, i.e., the existence of coupled states in the system, this embodiment selects... Figure 4 Two typical energy levels in the hollow hole transport spectrum -0.432eV and Spatial probability distribution calculation is performed using -0.420eV.

[0040] The calculation results show that: (1) For The state, whose probability density is in three quantum wells , , The distribution is significant in all cases, such as Figure 6 As shown in the figure. This result indicates that the state is formed by the coherent superposition of three well states, which is a typical strongly coupled state and fully reflects the characteristics of the multi-well cascaded coupled quantum structure in the system.

[0041] (2) and The states exhibit significant localization only in the first and third quantum wells, while they are almost undistributed in the central well, such as... Figure 7 This indicates that the state mainly originates from two side wells ( , The coupling of the neutron bands did not form an effective mixture with the intermediate trap.

[0042] Therefore, the MoS2 nanoribbon three-level coupled quantum well constructed in this embodiment achieves coherent multi-well coupling in a single material system. Its electronic states are controlled by both geometric boundaries and band shifts, exhibiting tunable coupling characteristics and a stable wavefunction superposition form. These results verify that the cascaded quantum well structure proposed in this invention can stably achieve coherent multi-well coupling in a MoS2 monolayer material, providing a reliable physical basis for subsequent geometric and electric field manipulation.

[0043] Example 2: Coupling characteristics under geometric parameter control (1) Barrier width control Based on the structure described in Example 1, to verify the influence of geometric parameters on the coherent coupling strength, the barrier width was adjusted. and the width of the central quantum well The two main parameters were systematically regulated and calculated.

[0044] The electron and hole transport spectra of this system follow The results of the changes are as follows Figure 8 , 9 As shown, this is a 3D heatmap, where x is the barrier width. y represents energy, and z represents the transport coefficient. When the internal barrier... , width At smaller sizes (around 2 nm), the wavefunctions of adjacent quantum wells overlap significantly, the tunneling channels are fully open, and the coupling strength is large, exhibiting a "strong coupling" characteristic. With... With increasing density (e.g., to 10–12 nm), the tunneling probability decreases, coherent coupling is limited, and energy level splitting decreases rapidly, even approaching a degenerate state. At this point, the structure tends to be a "weakly coupled" approximately independent quantum well system. However, in… At 12.1 nm, the transmission spectrum at this time is amplified as follows: Figure 10 Slight splitting can still be observed, indicating that the quantum tunneling effect has not completely subsided, and the system maintains finite coherent coupling. These results demonstrate that continuous manipulation from strong to weak coupling can be achieved through geometric design.

[0045] (2) Quantum well width modulation Furthermore, the electron and hole transport spectra of this system were calculated as follows: The results of the changes are as follows Figure 11 (Electrons), 12 (holes). This is a three-dimensional heatmap, where x is the barrier width. y represents Energy, and z represents the transport coefficient. The width of the central quantum well. It has a direct impact on the coherent coupling and wavefunction reconstruction of quantum states. Taking the electron as an example, as... The changes at approximately 1.8 nm and 3.9 nm show that the relevant energy levels gradually approach each other and exhibit obvious anti-crossing characteristics, indicating that the quantum coherent coupling of the system can be effectively regulated through geometric parameters.

[0046] In summary, Example 2 demonstrates that adjusting the barrier width It can continuously switch between strong and weak coupling; the width of the central trap can be adjusted. Energy level matching and anti-crossover control can be achieved through reasonable design. and The combination of these parameters allows for precise control of the energy level spacing and wavefunction reconstruction in multi-well systems. This geometric control mechanism provides a fundamental parameter window for subsequent electric field manipulation.

[0047] Example 3: Quantum Coupling Regulation under Electric Field Control Based on the geometric control described in Example 2, this example further adjusts the coupling strength and energy level matching of the multi-well system by applying an external electric field.

[0048] (1) Local electric field regulation A localized gate is arranged in the central quantum well region, and a localized electric field is applied. The local electric field primarily acts on the middle well, significantly altering its energy level positions, while having a smaller impact on the two side wells. We calculated the transmission spectrum as a function of the local electric field. Changes such as Figure 13 (electrons), 14 (holes), where x is the electric field. y represents energy, and z represents the transport coefficient. Calculation results show that, with... As the electric field increases, the central well level gradually shifts, approaching the energies of the two side well states and exhibiting a significant anti-crossover, resulting in enhanced inter-well coupling. When the electric field is removed from the resonance condition, the energy levels separate again, and the coupling is suppressed. This result demonstrates that a local electric field can rapidly and reversibly control the opening and closing of coherent states, enabling precise addressing of specific quantum channels.

[0049] (2) Global electric field control Apply a uniform global electric field Throughout the system, the energy levels of the three quantum wells and the barrier region undergo a global linear translation. We calculated the transmission spectrum as a function of the global electric field. Changes such as Figure 15 (electrons), 16 (holes), where x is the electric field. y represents energy, and z represents the transport coefficient. The results show that the energy levels move in the same direction and with similar slopes under the influence of the electric field, and no local anti-crossing phenomenon occurs, indicating that the global electric field is mainly used for overall energy level regulation.

[0050] (3) Overall adjustable features Local and global electric fields have complementary control functions: the former is used for fine selection and dynamic switching of specific energy levels, while the latter is used for coordinated translation and initial registration of the overall energy band. The combination of the two can realize a two-layer electric control mode of "coarse adjustment first, then fine adjustment", giving complex coupled systems more flexible adjustment characteristics than traditional methods.

[0051] In summary, Example 3 demonstrates that a local electric field can achieve selective modulation of specific energy levels and rapid switching of coherent states, while the global electric field is responsible for the coordinated shift of the overall energy band and the setting of initial conditions. By rationally combining the two electric field modes, precise control of energy level matching, coupling strength, and quantum state distribution in multi-well systems can be achieved. This electric field modulation mechanism enables the system to have dynamic adjustment capabilities driven by an external field, providing an effective means for the programmability and on-chip functional integration of quantum devices.

[0052] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A cascaded quantum well structure based on the difference of regional conductivity, characterized in that: S1, using a single-layer MoS2 nanoribbon as a structural base, zigzag edges and armchair edges are alternately arranged along the length direction of the nanoribbon, the zigzag edges are quantum well regions, and the armchair edges are barrier regions, forming a well-barrier unit; S2, defining the width of the well region and the width of the barrier region are geometric parameters; S3, according to the number and geometric parameters of the well-barrier units of the target cascaded quantum well structure, the well-barrier units in S1 are continuously transitioned along the edge direction of the nanoribbon to obtain the cascaded quantum well structure.

2. The cascade quantum well structure according to claim 1, wherein: The width of the nanoribbon keeps the distance between the upper and lower boundaries greater than 2 nm.

3. The cascade quantum well structure of claim 1, wherein: The zigzag edges and armchair edges in S1 are vertically connected and alternately arranged.

4. The cascade quantum well structure of claim 1, wherein: S2 each well region width 3 nm~ 6 nm, each barrier region width same.

5. The cascade quantum well structure of claim 1, wherein: The number of periods of the well-barrier unit of the cascaded quantum well structure is 3-15.

6. The method for coherent coupling control of the cascade quantum well structure according to any one of claims 1 to 5, characterized in that, It includes the following contents: 1) change the well width or the barrier width where the width is adjusted to achieve continuous switching between strong and weak coupling, the width is adjusted to achieve energy level matching and anti-crossing phenomenon control, and through reasonable design and combination, precise control of the energy level spacing of the multi-well system and wave function reconstruction is achieved; 2) electrodes are arranged at both ends of the cascaded quantum well structure, a horizontal electric field is applied to the structure to preliminarily adjust the energy level detuning between wells, coherent coupling based on spatial symmetry is realized, and then a vertical electric field is applied to the cascaded quantum well structure to accurately control the energy level position and coherent coupling strength between wells; 3) In the above control step, the transmission coefficient spectrum of the energy interval (-0.5eV~0.1eV) is calculated, and when the energy level splitting, anti-crossing characteristics or symmetric selective mixing are observed, it indicates that the system enters the controllable coherent coupling region. According to the test results, the coherent coupling energy interval [ , ] is determined, and the applied electric field is feedback corrected to lock the stable coherent state;​ Coherent coupling control of the cascaded quantum well structure is realized.

7. The control method according to claim 6, characterized in that: The vertical electric field in step 2) is a local electric field and / or a global electric field; Applying a local electric field is to set a local gate above or below one or more quantum well regions or gate voltage ; the local electric field causes two symmetry-matched energy levels to approach, and the system exhibits energy level anti-crossing characteristics, the wave function is reorganized and mixed, the coherent state switching is realized, and the specific quantum channel is accurately addressed; Applying a global electric field, an electric field is applied to the whole system or gate voltage , for overall energy level translation and system energy level balance, to achieve continuous adjustment while maintaining quantum state coherence.

8. The control method according to claim 6, characterized in that: The local electric field in step 2) is used for fine selection and dynamic switching of specific energy levels, and the global electric field is used for cooperative translation and initial registration of the overall energy band, and the combination of the two can realize a double-layer electric control mode of "rough adjustment first and then fine adjustment".

9. The control method according to claim 6, characterized in that: In step 3) the value of V is within -0.5 eV ~ 0.1 eV. , ] In step 3) the value of V is within -0.5 eV ~ 0.1 eV.

10. Application of the cascaded quantum well structure based on the difference of regional conductivity according to any one of claims 1-5 or the control method according to any one of claims 6-9 in on-chip quantum state modulation, logic quantum bit construction and / or design of adjustable energy band structure.

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