Superconducting current density measurement method, control system, storage medium, and electronic device

Abstract

Disclosed in the present invention are a superconducting current density measurement method, a control system, a storage medium, and an electronic device. The method comprises: determining a correspondence between a superconducting current density and a dynamic inductance of a sample under test, and connecting the sample under test to a resonant circuit; obtaining the dynamic inductance, and determining a resonant frequency on the basis of the dynamic inductance; and monitoring the resonant frequency, determining the change in the dynamic inductance on the basis of the change in the resonant frequency, and then obtaining, on the basis of the correspondence, the superconducting current density corresponding to the resonant frequency. The measurement method designed in the present application is not limited by the volume of the sample under test, and by monitoring the change in the resonant frequency with temperature or magnetic field, the change of the superconducting current density can be directly detected, thereby achieving accurate measurement of superconducting current densities of mesoscopic-scale (micro-nano level) samples and overcoming the problem of inaccurate measurement caused by weak signals in the conventional technology.

Description

A method for measuring superconducting current density, a control system, a storage medium, and an electronic device. Technical Field

[0001] This invention relates to the field of circuit quantum electrodynamics, and more particularly to a method for measuring superconducting current density, a control system, a storage medium, and an electronic device. Background Technology

[0002] The pairing mechanism of unconventional superconductors remains a puzzle in physics that has not yet been fully revealed. Unlike conventional superconductors, unconventional superconducting materials exhibit superconducting properties at relatively high temperatures, opening up more possibilities for the application of superconducting technology. However, the superconducting mechanism of these high-temperature superconducting materials has always been a challenge for the scientific community. Theoretically, it is predicted that the temperature dependence of superconducting current directly reflects the energy dependence of the quasi-particle density of states, thus reflecting the nodal structure of the superconducting order parameter.

[0003] Common techniques for measuring superconducting current density are based on considering its fundamental relationship with penetration depth, i.e., λ. -2 =μ0ρ s Then, several well-established experimental techniques are used to directly measure the temperature dependence of the penetration depth, such as dual-coil mutual inductance, tunnel diode oscillators, proximity diode oscillators, or cavity perturbation measurements. In fact, these measurements have proven to be extremely effective tools for identifying and probing non-traditional superconductors, especially crucial for identifying d-wave sequence parameters in cuprates.

[0004] A major limitation of traditional superconducting current density measurement techniques is that the magnitude of the measurement signal is directly affected by the sample volume. When the sample volume is very small, the measurement signal becomes extremely weak, or even impossible to measure effectively. This limits the ability of existing techniques to measure superconducting current density in mesoscopic (i.e., micro-nano scale) samples. Furthermore, with the emergence of two-dimensional non-traditional superconducting materials (such as molar graphene and other van der Waals materials), traditional measurement techniques are insufficient to meet the requirements for measuring the superconducting current density of these new materials. These new materials may possess different physical properties and superconducting mechanisms than traditional materials, thus necessitating new measurement techniques to accurately characterize their superconducting current density. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for measuring superconducting current density, a control system, a storage medium, and an electronic device.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for measuring superconducting current density, comprising:

[0007] Determine the relationship between the superconducting current density and dynamic inductance of the sample under test, and connect the sample under test to the resonant circuit.

[0008] Obtain the dynamic inductance, and determine the resonant frequency based on the dynamic inductance;

[0009] The resonant frequency is monitored, and the change in dynamic inductance is determined based on the change in the resonant frequency. Then, the superconducting current density corresponding to the resonant frequency is obtained based on the correspondence.

[0010] As a further description of the above technical solution: the correspondence between the superconducting current density and the dynamic inductance is determined based on the ratio of the cross-sectional area to the length of the sample to be tested.

[0011] As a further description of the above technical solution: the resonant circuit includes a resonant cavity inductor and a dynamic inductor of the sample under test, wherein the resonant cavity inductor and the dynamic inductor are connected in series.

[0012] As a further description of the above technical solution: the resonant circuit also includes a capacitor connected in parallel with the resonant cavity inductor and the dynamic inductor, one end of the capacitor being grounded.

[0013] As a further description of the above technical solution: the parameters of the resonant circuit include temperature and external magnetic field. In the initial state, the temperature is room temperature and the external magnetic field is zero. The total inductance of the resonant circuit is calculated to obtain a first result.

[0014] By changing the temperature and / or the external magnetic field, the total inductance is calculated to obtain a second result.

[0015] As a further description of the above technical solution: Based on the first result and the second result, the relationship between the ratio of the change value of dynamic inductance to the total inductance in the initial state and the ratio of the change value of resonant frequency to the resonant frequency in the initial state is obtained by calculation, so as to determine the change of dynamic inductance according to the change of resonant frequency when monitoring the change of resonant frequency.

[0016] As a further description of the above technical solution: the size of the sample to be tested is mesoscopic.

[0017] It also includes a control system, which is applicable to the measurement method described in any one of the above technical solutions, comprising:

[0018] The acquisition module acquires the resonant frequency of the resonant circuit.

[0019] The adjustment module adjusts the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample under test.

[0020] The monitoring module determines the change in superconducting current density by monitoring the change in resonant frequency and outputs the change result.

[0021] It also includes a computer-readable storage medium storing a computer program for running a measurement method, wherein the computer program causes a computer to perform the measurement method as described in any of the above technical solutions.

[0022] It also includes an electronic device, comprising:

[0023] One or more processors; memory; and

[0024] One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including a measurement method as described in any of the above technical solutions.

[0025] The above technical solution has the following advantages or beneficial effects:

[0026] 1. By monitoring the change in resonant frequency, based on the first and second results, the relationship between the ratio of the change in dynamic inductance to the total inductance in the initial state and the ratio of the change in resonant frequency to the resonant frequency in the initial state is calculated. According to the correspondence between superconducting current density and dynamic inductance, the change in superconducting current density is linked to the measurable circuit resonant frequency in the experiment. By monitoring the change in resonant frequency with temperature or magnetic field, the change in superconducting current density can be directly monitored, thus achieving accurate measurement of superconducting current density.

[0027] 2. The measurement method designed in this application is not limited by the size of the sample to be tested, and can accurately measure the superconducting current density on samples at the mesoscale (micro-nano level), overcoming the problem of inaccurate measurement caused by weak signals in traditional techniques. Attached Figure Description

[0028] Figure 1 is a flowchart of the measurement method proposed in this invention;

[0029] Figure 2 is a schematic diagram of the control system proposed in this invention;

[0030] Figure 3 is a schematic diagram of the resonant circuit in this invention;

[0031] Figure 4 is a schematic diagram showing the relationship between the resonant circuit parameters and the resonant frequency in this invention.

[0032] Figure 5 is a schematic diagram showing the temperature dependence of resonant frequency and superconducting current density in this invention.

[0033] Legend:

[0034] 1. Data Acquisition Module; 2. Adjustment Module; 3. Monitoring Module. Detailed Implementation

[0035] 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.

[0036] Referring to Figure 1, one embodiment of the present invention provides a method for measuring superconducting current density, comprising: determining the correspondence between the superconducting current density of the sample to be tested and the dynamic inductance; connecting the sample to be tested to a resonant circuit; acquiring the dynamic inductance; determining the resonant frequency based on the dynamic inductance; monitoring the resonant frequency; determining the change in the dynamic inductance based on the change in the resonant frequency; and then obtaining the superconducting current density corresponding to the resonant frequency based on the correspondence.

[0037] The applicant discovered in their research that the pairing mechanism of unconventional superconductivity remains a puzzle in physics. Unconventional superconductors are materials whose superconducting properties do not conform to the conventional superconductivity theory (BCS theory). While the BCS theory primarily explains superconductivity in metals caused by electron-phonon coupling, the superconducting mechanism of unconventional superconductors is far more complex and remains incompletely understood. In unconventional superconductors, the electron pairing mechanism differs from that in conventional superconductors. Besides the traditional s-wave pairing, p-wave and d-wave pairing also exist. These pairing mechanisms may be related to strong electron correlation, magnetic interactions, spin fluctuations, and other factors. Furthermore, the specific form and description of the superconducting order parameter in unconventional superconductors may differ from those in conventional superconductors because the high-temperature superconductivity mechanism differs from the BCS theory.

[0038] Unlike conventional superconductors, unconventional superconducting materials exhibit superconducting properties at relatively high temperatures, offering more possibilities for the application of superconducting technology. However, the superconducting mechanism of these high-temperature superconducting materials has always been a challenge for the scientific community. Theoretically, it is predicted that the temperature dependence of superconducting current directly reflects the energy dependence of quasiparticle density of states, thus reflecting the nodal structure of the superconducting order parameter. For example, in a point-node system, we have found that δρ s (T) / ρ s (0)∝T 2 For line nodes, we find δρ s (T) / ρ s (0)∝T, where δ represents a small change and ∝ represents a proportional relationship.

[0039] In this scheme, we design a measurement method for detecting superconducting current density based on the principle of Circuit Quantum Electrodynamics (cQED), and then describe the experimental scheme to prove its technical feasibility.

[0040] cQED, a technique combining quantum optics and circuit electrodynamics, has shown great potential in fields such as quantum information processing and quantum computing. By utilizing the dynamic inductance measurement method of cQED, this invention achieves precise measurement of superconducting current density in mesoscopic samples. This will provide strong support for studying the physical properties and superconducting mechanisms of non-traditional superconducting materials and promote further development in related fields.

[0041] In this embodiment, the specific steps of the superconducting current density measurement method are as follows:

[0042] S1: Determine the relationship between the superconducting current density and dynamic inductance of the sample under test, and connect the sample under test to the resonant circuit.

[0043] S2: Obtain the dynamic inductance and determine the resonant frequency based on the dynamic inductance;

[0044] S3: Monitor the resonant frequency, determine the change in dynamic inductance based on the change in the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency based on the corresponding relationship.

[0045] The designed measurement method is not limited by the size of the sample. By monitoring the change of resonant frequency with temperature or magnetic field, the change of superconducting current density can be directly monitored. It can accurately measure the superconducting current density on samples at the mesoscale (micro-nano level), overcoming the problem of inaccurate measurement caused by weak signals in traditional techniques.

[0046] The relationship between superconducting current density and dynamic inductance is determined based on the ratio of the cross-sectional area to the length of the sample under test.

[0047] In this embodiment, the sample size is mesoscopic. The measurement is achieved using the relationship between superconducting current density and dynamic inductance. The algorithm formula is as follows:

[0048] Where l is the length of the sample to be tested, A is the cross-sectional area of ​​the sample to be tested, and L K For dynamic inductance, ρ S This represents the superconducting current density.

[0049] Dynamic inductance is large in the following two cases: (1) when the geometric factor is large (1) In smaller samples; (2) In materials with low superconducting current density. Both of these cases will apply to the mesoscale materials of interest in this invention, where dynamic inductance accounts for a significant proportion of the total inductance of the device under study.

[0050] Referring to Figure 3, the resonant circuit includes a resonant cavity inductor and a dynamic inductor of the sample under test, with the resonant cavity inductor and the dynamic inductor connected in series. The resonant circuit also includes a capacitor connected in parallel with the resonant cavity inductor and the dynamic inductor, with one end of the capacitor grounded.

[0051] In this embodiment, the sample under test is connected as a component in an LC resonant circuit. The dynamic inductance of the sample under test is connected in series with the resonant cavity inductance. The total inductance of the resonant circuit consists of the resonant cavity inductance (Lr) and the dynamic inductance (Ln) of the sample under test. K The resonant frequency of the resonant circuit is jointly determined by these two inductors. Typically, the dynamic inductance is a function of temperature, magnetic field, or other parameters (such as the carrier density in the test material where the gate voltage is adjustable). The formula for calculating the resonant frequency is as follows:

[0052] L tot =L r +L K ;

[0053] ω r =(L tot C r ) -1 / 2 ;

[0054] Where, ω r L is the resonant frequency. tot Let Cr be the total inductance, and Cr be the capacitance of the resonant circuit. Capacitance is a constant that is independent of temperature and magnetic field.

[0055] Then, the total inductance L tot =L r +L K The formula is changed as follows:

[0056] L tot (T, H) = L0 + δ LK (T, H);

[0057] Where T is temperature, H is magnetic field, and L0 = L r +L K (0, 0) is the total inductance at room temperature and zero external magnetic field. Ltot(T, H) is the total inductance of the resonant circuit at temperature T and magnetic field H, δL K It represents a small amount of dynamic inductance change.

[0058] In the initial state, with the temperature at room temperature and the external magnetic field at zero, the total inductance of the resonant circuit is calculated to obtain the first result; by changing the temperature or the external magnetic field, the total inductance is calculated to obtain the second result; and the difference between the dynamic inductance change is calculated based on the first and second results.

[0059] In this embodiment, the dynamic inductance changes with temperature and magnetic field. Since the size of the sample under test is mesoscopic, δL K (T, H) = L K (T, H)-L K (0,0) can be assumed to be a small quantity.

[0060] Furthermore, based on the first and second results, the relationship between the ratio of the change in dynamic inductance to the total inductance in the initial state and the ratio of the change in resonant frequency to the resonant frequency in the initial state is calculated. This enables the determination of the change in dynamic inductance based on the change in resonant frequency when monitoring the change in resonant frequency. Specifically:

[0061] The change in resonant frequency is as follows:

[0062] δω r =ω r (T,H)-ω0;

[0063] δω r This represents the change in resonant frequency, which is usually a small amount, and is expanded as follows:

[0064] in The ratio is usually very small, around 10. -6 -10 -5 .

[0065] Furthermore, use By relating the dynamic inductance to the superconducting current density and expanding it to the linear order, the relationship between the resonant frequency change and the superconducting current density change can be obtained, as follows:

[0066] Where α is the dynamic inductance fraction, defined as:

[0067] Furthermore, by monitoring the change of resonant frequency with temperature and / or magnetic field, and based on the above relationship between the change of resonant frequency and the change of superconducting current density, the superconducting current density can be accurately measured by monitoring the change of resonant frequency.

[0068] Specifically, in some embodiments, a two-dimensional van der Waals magnetic material such as NiPS3 with a thickness of 10-50 nm is used as the sample to be tested and connected to an LC resonant circuit. Based on the resonant cavity inductance Lr and capacitance Cr of the resonant circuit, the relationship between the resonant frequency and the dynamic inductance is calculated. Here, the resonant cavity inductance Lr and capacitance Cr are constants independent of temperature and magnetic field. Depending on the actual circuit connection, in this embodiment, to ensure the resonant cavity frequency is 3.8 GHz, the capacitance Cr is generally designed to be 90-110 fF, the resonant cavity inductance Lr to be 7600-8000 nH, and the dynamic inductance Lk to be 0-100 nH. By monitoring the change of the resonant frequency with temperature, the corresponding superconducting current density is obtained, as shown in Figure 4. Specifically, at a temperature of 0.05 K and a resonant frequency of 3.80002 eV / L, the superconducting current density is... 9 At that time, the superconducting current density changed by 6.57e -6 See Table 1 for details:

[0069] Table 1

[0070] This invention overcomes the measurement inaccuracies caused by weak signals in traditional techniques. In Figure 4, the S21 parameter describes the insertion loss, measuring the power attenuation of the signal after passing through the system. In particular, by monitoring the change in resonant frequency with temperature, the temperature dependence of superconducting current density can be determined (see Figure 5). With the emergence of non-traditional superconducting materials, traditional measurement techniques cannot meet the requirements for measuring their superconducting current density. This invention provides a novel measurement technique for the physical properties and superconducting mechanisms of these new materials, accurately characterizing their superconducting current density. This helps to understand the nodal structure of superconductors and provides important support for studying their physical properties.

[0071] In some implementation methods:

[0072] Referring to Figure 2, a control system is provided, which is applicable to the measurement method of any of the above-described technical solutions, comprising:

[0073] Acquisition module 1 acquires the resonant frequency of the resonant circuit;

[0074] Adjustment module 2 adjusts the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample under test;

[0075] Monitoring module 3 determines the change in superconducting current density by monitoring the change in resonant frequency and outputs a change result.

[0076] It is understood that the control system provided in the embodiments of the present invention corresponds to the above measurement method, and the explanation, examples, beneficial effects, etc. of its contents can be referred to the corresponding contents in the measurement method, which will not be repeated here.

[0077] In some implementation methods:

[0078] A computer-readable storage medium storing a computer program for running a measurement method, wherein the computer program causes a computer to perform the following steps:

[0079] S1: Determine the relationship between the superconducting current density and dynamic inductance of the sample under test, and connect the sample under test to the resonant circuit.

[0080] S2: Obtain the dynamic inductance and determine the resonant frequency based on the dynamic inductance;

[0081] S3: Monitor the resonant frequency, determine the change in dynamic inductance based on the change in the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency based on the corresponding relationship.

[0082] In some implementation methods:

[0083] An electronic device, comprising:

[0084] One or more processors; memory; and

[0085] One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including steps for performing the following:

[0086] S1: Determine the relationship between the superconducting current density and dynamic inductance of the sample under test, and connect the sample under test to the resonant circuit.

[0087] S2: Obtain the dynamic inductance and determine the resonant frequency based on the dynamic inductance;

[0088] S3: Monitor the resonant frequency, determine the change in dynamic inductance based on the change in the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency based on the corresponding relationship.

[0089] It should be noted that, through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the prior art, can be embodied in the form of software products. These computer software products can be stored in computer-readable storage media, such as ROM / RAM, magnetic disks, optical disks, etc., and include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or certain portions of the embodiments. In this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In the absence of further restrictions, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0090] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring superconducting current density, characterized in that, include: Determine the relationship between the superconducting current density and dynamic inductance of the sample under test, and connect the sample under test to the resonant circuit. Obtain the dynamic inductance, and determine the resonant frequency based on the dynamic inductance; The resonant frequency is monitored, and the change in dynamic inductance is determined based on the change in the resonant frequency. Then, the superconducting current density corresponding to the resonant frequency is obtained based on the correspondence.

2. The measurement method according to claim 1, characterized in that: The correspondence between the superconducting current density and the dynamic inductance is determined based on the ratio of the cross-sectional area to the length of the sample under test.

3. The measurement method according to claim 1, characterized in that: The resonant circuit includes a resonant cavity inductor and a dynamic inductor of the sample under test, wherein the resonant cavity inductor and the dynamic inductor are connected in series.

4. The measurement method according to claim 3, characterized in that: The resonant circuit further includes a capacitor connected in parallel with the resonant cavity inductor and the dynamic inductor, one end of which is grounded.

5. The measurement method according to claim 1, characterized in that: The parameters of the resonant circuit include temperature and external magnetic field. In the initial state, the temperature is room temperature and the external magnetic field is zero. The total inductance of the resonant circuit is calculated to obtain the first result. By changing the temperature and / or the external magnetic field, the total inductance is calculated to obtain a second result.

6. The measurement method according to claim 5, characterized in that: Based on the first and second results, the relationship between the ratio of the change in dynamic inductance to the total inductance in the initial state and the ratio of the change in resonant frequency to the resonant frequency in the initial state is calculated. This enables the determination of the change in dynamic inductance based on the change in resonant frequency when monitoring the change in resonant frequency.

7. The measurement method according to claim 1, characterized in that: The size of the sample to be tested is mesoscopic.

8. A control system, characterized in that, The control system is applicable to the measurement method according to any one of claims 1-7, comprising: The acquisition module acquires the resonant frequency of the resonant circuit. The adjustment module adjusts the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample under test. The monitoring module determines the change in superconducting current density by monitoring the change in resonant frequency and outputs the change result.

9. A computer-readable storage medium, characterized in that, It stores a computer program for running a measurement method, wherein the computer program causes a computer to perform the measurement method as described in any one of claims 1-7.

10. An electronic device, characterized in that, include: One or more processors; Memory; as well as One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including methods for performing the measurement method as described in any one of claims 1-7.

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