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

Abstract

The invention discloses a superconducting current density measurement method, a control system, a storage medium and electronic equipment, and the method comprises the steps: determining a corresponding relation between the superconducting current density of a to-be-measured sample and dynamic inductance, and connecting the to-be-measured sample with a resonant circuit; obtaining dynamic inductance, and determining resonant frequency according to the dynamic inductance; monitoring the resonant frequency, determining the change of the dynamic inductance according to the change of the resonant frequency, and obtaining the superconducting current density corresponding to the resonant frequency according to the corresponding relation; the measuring method designed by the invention is not limited by the volume of the sample to be measured, the change of the superconducting current density can be directly monitored by monitoring the change of the resonant frequency temperature or the magnetic field, the superconducting current density can be accurately measured on the mesoscale (micro-nano scale) sample, and the measurement accuracy is high. The problem of inaccurate measurement caused by weak signals in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of circuit quantum electrodynamics, and in particular to a superconducting current density measurement method, a control system, a storage medium and an electronic device. Background Art

[0002] The pairing mechanism of unconventional superconductors is a mystery in physics that has not yet been fully revealed. Unlike conventional superconductors, unconventional superconducting materials can exhibit superconducting properties at relatively high temperatures, which provides 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 the superconducting current directly reflects the energy dependence of the quasiparticle state density, thereby reflecting the node structure of the superconducting order parameter.

[0003] The commonly used technique for measuring superconducting current density is to consider its fundamental relationship with the penetration depth, namely, λ -2 =μ0ρ s The temperature dependence of the penetration depth is then measured directly using well-established experimental techniques such as two-coil mutual inductance, tunnel diode oscillators, neighbor diode oscillators or cavity perturbation measurements. In fact, these measurements have proven to be extremely powerful tools for identifying and probing unconventional superconductors, and are especially crucial for the identification of the d-order parameter in cuprates.

[0004] There is a major limitation in the traditional superconducting current density measurement technology, that is, the size of the measurement signal is directly affected by the sample volume. When the sample volume is very small, the measurement signal becomes very weak, or even impossible to measure effectively. This limits the ability of existing technologies to measure superconducting current density on mesoscopic scale (i.e., micro-nanoscale) samples. At the same time, with the emergence of two-dimensional non-traditional superconducting materials (such as mole graphene and other van der Waals materials), traditional measurement techniques cannot meet the demand for superconducting current density measurements of these new materials. These new materials may have different physical properties and superconducting mechanisms from traditional materials, so new measurement techniques are needed to accurately characterize their superconducting current density. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a superconducting current density measurement method, control system, storage medium and electronic equipment.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a method for measuring superconducting current density, comprising:

[0007] Determine the corresponding relationship between the superconducting current density and the dynamic inductance of the sample to be tested, and connect the sample to be tested to the resonant circuit;

[0008] Acquire dynamic inductance, and determine the resonant frequency according to the dynamic inductance;

[0009] The resonant frequency is monitored, a change in the dynamic inductance is determined according to a change in the resonant frequency, and then the superconducting current density corresponding to the resonant frequency is obtained according to the corresponding relationship.

[0010] As a further description of the above technical solution: the corresponding relationship between the superconducting current density and the dynamic inductance is determined according to 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 to be tested, and 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 inductance and the dynamic inductance, and one end of the capacitor is grounded.

[0013] As a further description of the above technical solution: the parameters of the resonant circuit include temperature and external magnetic field. In an 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] The temperature and / or the external magnetic field are changed, and 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 the dynamic inductance to the total inductance in the initial state and the ratio of the change value of the resonant frequency to the resonant frequency in the initial state is obtained by calculation, so that when monitoring the change of the resonant frequency, the change of the dynamic inductance is determined according to the change of the resonant frequency.

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

[0017] Also included is a control system, which is applicable to the measurement method described in any one of the above technical solutions, including:

[0018] An acquisition module is used to acquire the resonant frequency of the resonant circuit;

[0019] An adjustment module, which adjusts the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample to be tested;

[0020] The monitoring module determines the change of superconducting current density by monitoring the change of resonance frequency and outputs a change result.

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

[0022] Also included is 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 are configured to be executed by the one or more processors, and the programs include a method for executing the measurement method described in any one of the above technical solutions.

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

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

[0027] 2. The measurement method designed in this application is not limited by the volume of the sample to be measured, and can accurately measure the superconducting current density on samples at the mesoscopic scale (micro-nano level), overcoming the problem of inaccurate measurement caused by weak signals in traditional technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart of the measurement method proposed by the present invention;

[0029] Figure 2 It is a structural schematic diagram of the control system proposed by the present invention;

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

[0031] Figure 4 A schematic diagram of the relationship between the resonant circuit parameters and the resonant frequency in the present invention;

[0032] Figure 5 Schematic diagram of the temperature dependence of the resonant frequency and superconducting current density in the present invention.

[0033] Legend:

[0034] 1. Acquisition module; 2. Adjustment module; 3. Monitoring module. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Reference Figure 1 An embodiment of the present invention provides: a method for measuring superconducting current density, comprising: determining the corresponding relationship between the superconducting current density and the dynamic inductance of a sample to be measured, connecting the sample to be measured to a resonant circuit; obtaining the dynamic inductance, and determining the resonant frequency according to the dynamic inductance; monitoring the resonant frequency, determining the change of the dynamic inductance according to the change of the resonant frequency, and then obtaining the superconducting current density corresponding to the resonant frequency according to the corresponding relationship.

[0037] The applicant discovered in the study that the pairing mechanism of unconventional superconductors is a mystery in physics that has not yet been fully revealed. Unconventional superconductors refer to materials whose superconducting properties do not conform to the traditional superconductivity theory (i.e., BCS theory). The BCS theory mainly explains the superconductivity phenomenon in metals caused by electron-phonon coupling, but the superconductivity mechanism of unconventional superconductors is more complicated and has not yet been fully revealed. In unconventional superconductors, the pairing mechanism of electrons is different from that of traditional superconductors. In addition to the traditional s-wave pairing, there are also p-wave pairing, d-wave pairing, etc. These pairing mechanisms may be related to factors such as strong correlations between electrons, magnetic interactions, and spin fluctuations. At the same time, in unconventional superconductors, the specific form and description of the superconducting order parameter may be different from those of traditional superconductors because the high-temperature superconductivity mechanism is different from the BCS theory.

[0038] Unlike conventional superconductors, unconventional superconducting materials can exhibit superconducting properties at relatively high temperatures, which provides 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 the superconducting current directly reflects the energy dependence of the quasiparticle state density, thereby reflecting the node structure of the superconducting order parameter. For example, for a system of point nodes, we find that δρ s (T) / ρ s (0)∝T 2 , and for line nodes, we find that δρ s (T) / ρ s (0)∝T, where δ represents a small amount of change and ∝ represents a relationship proportional to .

[0039] In this proposal, we design a measurement method for probing superconducting current density based on the principle of circuit quantum electrodynamics (cQED), and then describe an experimental scheme to demonstrate its technical feasibility.

[0040] cQED is a technology that combines quantum optics and circuit electrodynamics, and has shown great potential in fields such as quantum information processing and quantum computing. By using the dynamic inductance measurement method of cQED, the present invention achieves accurate measurement of superconducting current density of mesoscopic samples, which 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 method for measuring superconducting current density are as follows:

[0042] S1: Determine the corresponding relationship between the superconducting current density and the dynamic inductance of the sample to be tested, and connect the sample to be tested to the resonant circuit;

[0043] S2: Obtain dynamic inductance and determine the resonant frequency according to the dynamic inductance;

[0044] S3: monitor the resonant frequency, determine the change of dynamic inductance according to the change of the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency according to the corresponding relationship.

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

[0046] The corresponding relationship between superconducting current density and dynamic inductance is determined according to the ratio of the cross-sectional area to the length of the sample to be tested.

[0047] In this embodiment, the size of the sample to be measured is mesoscopic, and the relationship between superconducting current density and dynamic inductance is used to achieve measurement. The algorithm formula is as follows:

[0048]

[0049] 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 is the dynamic inductance, ρ s is the superconducting current density.

[0050] The dynamic inductance will be large in the following two cases: (1) When the geometric factor (1) In a small sample; (2) In a material with a low superconducting current density. These two situations will apply to the mesoscopic scale materials concerned by the present invention, so that the dynamic inductance occupies a considerable proportion of the total inductance of the research device.

[0051] Reference Figure 3 The resonant circuit includes a resonant cavity inductor and a dynamic inductor of the sample to be tested, the resonant cavity inductor and the dynamic inductor are connected in series; the resonant circuit also includes a capacitor connected in parallel with the resonant cavity inductor and the dynamic inductor, one end of the capacitor is grounded.

[0052] In this embodiment, the sample to be tested is connected to the LC resonant circuit as a component, and the dynamic inductance of the sample to be tested is connected in series with the resonant cavity inductance. The total inductance of the resonant circuit is composed of the resonant cavity inductance (Lr) of the circuit and the dynamic inductance (Lr) of the material to be tested. K ) are jointly determined. Usually, the dynamic inductance is a function of temperature, magnetic field or other parameters (such as the gate voltage-adjustable carrier density in the material to be tested). Therefore, these two inductors jointly determine the resonant frequency of the resonant circuit. The resonant frequency algorithm formula is as follows:

[0053] L tot =L r +L K ;

[0054] ω r =(L tot C r ) -1 / 2 ;

[0055] Among them, ω r is the resonant frequency, L tot is the total inductance, Cr is the capacitance of the resonant circuit, and the capacitance is a constant that is independent of temperature and magnetic field.

[0056] Then, the total inductance L tot =L r +L K The formula is changed:

[0057] L tot (T, H) = L0 + δL K (T, H);

[0058] Where T is temperature, H is magnetic field, L0 = L r +L K (0, 0) is the total inductance when the temperature is room temperature and the external magnetic field is zero. Ltot(T, H) is the total inductance of the resonant circuit when the temperature is T and the magnetic field is H, δL K A small amount representing the change in dynamic inductance.

[0059] In the initial state, the temperature is room temperature and the external magnetic field is zero, and the total inductance of the resonant circuit is calculated to obtain a first result; the temperature or the external magnetic field is changed, and the total inductance is calculated to obtain a second result, and the difference in dynamic inductance change is calculated based on the first result and the second result.

[0060] In this embodiment, the dynamic inductance changes with temperature and magnetic field. Since the size of the sample to be tested is mesoscopic, δL K (T, H) = L K (T, H)-L K (0,0) can be assumed to be a small amount,

[0061] Further, based on the first result and the second result, the relationship between the ratio of the change value of the dynamic inductance to the total inductance in the initial state and the ratio of the change value of the resonant frequency to the resonant frequency in the initial state is obtained by calculation, so that when monitoring the change of the resonant frequency, the change of the dynamic inductance is determined according to the change of the resonant frequency, specifically:

[0062] The change in resonant frequency is:

[0063] δω r =ω r (T, H)-ω0;

[0064]

[0065] δω r It represents the change in resonant frequency, which is usually a small amount, and is expanded into:

[0066]

[0067] in The ratio is usually small, about 10 -6 -10 -5 .

[0068] Further, use By correlating the dynamic inductance with the superconducting current density and expanding it to the linear order again, we can get the relationship between the change of the resonant frequency and the change of the superconducting current density, as follows:

[0069]

[0070] Where α is the dynamic inductance fraction, defined as:

[0071]

[0072] Furthermore, by monitoring the change of the resonant frequency with temperature and / or magnetic field, based on the above relationship between the change of the resonant frequency and the change of the superconducting current density, the superconducting current density can be accurately measured by monitoring the change of the resonant frequency.

[0073] Specifically, in some embodiments, a material such as NiPS3 or other two-dimensional van der Waals magnetic material with a thickness of 10-50nm is used as a sample to be tested and connected to an LC resonant circuit. According to the resonant cavity inductance Lr and capacitance Cr of the resonant circuit, the relationship formula between the resonant frequency and the dynamic inductance is calculated, wherein the resonant cavity inductance Lr and the capacitance Cr are constants independent of temperature and magnetic field. According to the actual circuit connection settings, in order to ensure that the resonant cavity frequency is 3.8GHz, the capacitance Cr is generally designed to be 90-110fF, the resonant cavity inductance Lr is 7600-8000nH, and the dynamic inductance Lk is 0-100nH. By monitoring the change of the resonant frequency with temperature, the corresponding superconducting current density is obtained, such as Figure 4 Specifically, when the temperature is 0.05K, the resonant frequency is 3.80002e 9 When the superconducting current density changes to 6.57e -6 , see Table 1 for details:

[0074] Table 1

[0075]

[0076] It overcomes the problem of inaccurate measurement caused by weak signals in traditional technologies. Figure 4 In the case of S21, the insertion loss is described, which measures the power attenuation of the signal after it passes through the system. In particular, by monitoring the change in resonant frequency with temperature, the temperature dependence of the superconducting current density can be determined (see Figure 5 ), with the emergence of non-traditional superconducting materials, traditional measurement technology cannot meet the measurement needs of their superconducting current density. The present invention provides a new measurement technology for the physical properties and superconducting mechanism of these new materials, which can accurately characterize their superconducting current density, which helps to understand the node structure of superconductors and provides important support for studying their physical properties.

[0077] In some embodiments:

[0078] Reference Figure 2 , a control system, the control system is applicable to the measurement method of any one of the above technical solutions, including:

[0079] Acquisition module 1, collecting the resonant frequency of the resonant circuit;

[0080] The regulating module 2 regulates the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample to be tested;

[0081] The monitoring module 3 determines the change of the superconducting current density by monitoring the change of the resonant frequency and outputs a change result.

[0082] It is understandable that the control system provided in the embodiment of the present invention corresponds to the above-mentioned measurement method, and the explanations, examples, beneficial effects and other parts of the relevant contents can refer to the corresponding contents in the measurement method, which will not be repeated here.

[0083] In some embodiments:

[0084] A computer-readable storage medium stores a computer program for executing a measurement method, wherein the computer program causes a computer to execute the following steps:

[0085] S1: Determine the corresponding relationship between the superconducting current density and the dynamic inductance of the sample to be tested, and connect the sample to be tested to the resonant circuit;

[0086] S2: Obtain dynamic inductance and determine the resonant frequency according to the dynamic inductance;

[0087] S3: monitor the resonant frequency, determine the change of dynamic inductance according to the change of the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency according to the corresponding relationship.

[0088] In some embodiments:

[0089] An electronic device, comprising:

[0090] one or more processors; memory; and

[0091] 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 comprising steps for performing the following steps:

[0092] S1: Determine the corresponding relationship between the superconducting current density and the dynamic inductance of the sample to be tested, and connect the sample to be tested to the resonant circuit;

[0093] S2: Obtain dynamic inductance and determine the resonant frequency according to the dynamic inductance;

[0094] S3: monitor the resonant frequency, determine the change of dynamic inductance according to the change of the resonant frequency, and then obtain the superconducting current density corresponding to the resonant frequency according to the corresponding relationship.

[0095] It should be noted that, through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiment. In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or device. Without more constraints, an element defined by the phrase "comprising a..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

[0096] Finally, it should be noted that the above 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 aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring superconducting current density, characterized in that: include: Determine the corresponding relationship between the superconducting current density and the dynamic inductance of the sample to be tested, and connect the sample to be tested to the resonant circuit; Acquire dynamic inductance, and determine the resonant frequency according to the dynamic inductance; The resonant frequency is monitored, a change in the dynamic inductance is determined according to a change in the resonant frequency, and then the superconducting current density corresponding to the resonant frequency is obtained according to the corresponding relationship.

2. The measuring method according to claim 1, characterized in that: The corresponding relationship between the superconducting current density and the dynamic inductance is determined according to the ratio of the cross-sectional area to the length of the sample to be tested.

3. The measuring method according to claim 1, characterized in that: The resonant circuit comprises a resonant cavity inductor and a dynamic inductor of the sample to be tested, and the resonant cavity inductor and the dynamic inductor are connected in series.

4. The measuring 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, and one end of the capacitor is grounded.

5. The measuring method according to claim 1, characterized in that: The parameters of the resonant circuit include temperature and external magnetic field. In an 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. The temperature and / or the external magnetic field are changed, and the total inductance is calculated to obtain a second result.

6. The measuring method according to claim 5, characterized in that: Based on the first result and the second result, a relationship between a ratio of a change value of the dynamic inductance to the total inductance in an initial state and a ratio of a change value of the resonant frequency to the resonant frequency in an initial state is obtained by calculation, so that when monitoring the change of the resonant frequency, the change of the dynamic inductance is determined according to the change of the resonant frequency.

7. The measuring 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 described in any one of claims 1 to 7, including: An acquisition module is used to acquire the resonant frequency of the resonant circuit; An adjustment module, which adjusts the temperature of the resonant circuit or the external magnetic field to control the dynamic inductance change of the sample to be tested; The monitoring module determines the change of superconducting current density by monitoring the change of resonance frequency and outputs a change result.

9. A computer-readable storage medium, characterized in that: The computer stores a computer program for running the measurement method, wherein the computer program enables a computer to execute the measurement method according to any one of claims 1 to 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 comprising instructions for executing the measurement method according to any one of claims 1 to 7.

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