High-sensitivity superconducting magnetic detection device and method based on NV color center under high pressure and low temperature

Abstract

The invention provides a high-sensitivity superconducting magnetic detection device and method based on an NV color center under high pressure and low temperature. The high-sensitivity superconducting magnetic detection device comprises a microwave emission module, an optical excitation module, an imaging module, a fluorescence collection module, a data collection and control module, a diamond anvil cell, a low-temperature test module and a magnet module. The method has the beneficial effects that the diamond injected with the NV color center serves as the anvil cell of the diamond anvil cell, and high-pressure and low-temperature conditions are synchronously obtained in liquid helium and liquid nitrogen temperature zones; according to the invention, in-situ pressure measurement can be realized under high pressure, and ruby or Raman standard pressure is not needed; a sample is placed in the diamond anvil cell, the diamond anvil cell is placed in the low-temperature cavity, the lowest temperature of 4K and in-situ pressurization can be realized by using the low-temperature test module, and the quality of a microwave signal transmitted by the low-temperature semi-steel cable is higher and the loss is smaller by using the low-temperature semi-steel cable. And the superconducting property of the material at low temperature and high pressure is quantitatively tested under the condition of high integration.

Description

Technical Field

[0001] This invention relates to the field of physical property measurement and characterization technology under extreme conditions, and in particular to a highly sensitive superconducting magnetic detection device and method based on NV color centers under high pressure and low temperature. Background Technology

[0002] Superconductors are a class of materials that exhibit zero electrical resistance and perfect diamagnetism (Meissner effect) under specific conditions. Their research significance encompasses multiple levels, including scientific exploration, technological innovation, and industrial applications. At ambient pressure, the critical temperature of most superconducting materials is relatively low (e.g., 23.2 K for Nb3Ge). However, high pressure can significantly increase the critical temperature (T) by enhancing electron correlation or introducing new quantum states. C In addition, some materials that are not superconducting at normal pressure can become superconducting under high pressure, such as hydrides (e.g., H3S, LaH2O) under high pressure. 10 The superconductivity exhibited near-room temperature (above 200K) and provided new clues for understanding the mechanism of high-temperature superconductivity. Therefore, in recent years, high-pressure technology has become an important means of studying superconducting materials.

[0003] The diamond anvil cell (DAC) is a widely used experimental device for generating high pressures, capable of achieving static pressures of hundreds of GPa. Experiments have demonstrated that optically probed magnetic resonance spectroscopy using diamond nitrogen-vacancy centers (NV centers) can be used to detect localized magnetic fields. Therefore, integrating NV centers with a DAC allows for the detection of one of the key conditions for superconductivity—the Meissner effect. However, due to limitations in high-pressure technology, current high-pressure superconducting NV center detection systems are difficult to directly connect to cryogenic conditions; current cryogenic NV center detection systems suffer from significant microwave losses; conventional cryogenic cavities cannot directly pressurize the compressor under cryogenic conditions; and diamond and ruby ​​standard voltage (DSV) systems require redesigned optical paths or external instruments, making integration less straightforward. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a high-sensitivity superconducting magnetic detection device and method based on NV centers under high pressure and low temperature, so as to solve the problem that the current NV center system for high pressure superconducting detection is difficult to directly connect with low temperature conditions.

[0005] To achieve the above and other related objectives, the present invention provides the following technical solution:

[0006] A high-sensitivity superconducting magnetic detection device based on NV centers under high pressure and low temperature includes a microwave emission module, an optical excitation module, an imaging module, a fluorescence collection module, a data collection and control module, a diamond anvil cell, a low-temperature testing module, and a magnet module. The microwave emission module generates microwaves of a specific frequency, which are transmitted to the diamond anvil cell to manipulate the spin state of the NV centers. The optical excitation module generates laser light to modulate the spin state of the NV centers, enabling them to initialize and undergo radiative transitions. The imaging module acquires the relative position information between the laser light transmitted from the optical excitation module and the sample, and feeds this information back to the data collection and control module. The fluorescence collection module collects relevant information generated in the diamond anvil cell under the manipulation of the microwave emission module and the optical excitation module, and transmits the collected information to the data collection and control module.

[0007] The data collection and control module is used to control the microwave emission module and receive information from the imaging module and the fluorescence collection module. Based on the information from the imaging module, it adjusts the relative position of the laser emitted by the optical excitation module and the sample. Based on the information from the fluorescence collection module, it determines the photodetector magnetic resonance spectrum of the sample at different temperatures. The diamond anvil cell is used to place the sample and generate a high-pressure environment. The low-temperature testing module is used to place the diamond anvil cell, provide low-temperature conditions, and transmit the microwave signal from the microwave emission module to the diamond anvil cell. The magnet module is used to apply a magnetic field to the diamond anvil cell.

[0008] In one embodiment of the present invention, the microwave transmitting module includes a microwave source for generating microwaves, a microwave switch for controlling the microwave switch, a power amplifier for amplifying microwave signal power, a load for preventing amplifier damage, and a circulator for realizing unidirectional signal transmission, all electrically connected in sequence along the microwave transmission path via wires. The microwave source is electrically connected to the data collection and control module via wires.

[0009] In one embodiment of the present invention, the optical excitation module includes a laser for generating laser light, arranged sequentially along the laser emission optical path, a dichroic mirror for separating light into different wavelengths and propagating in different directions, a first lens and a second lens for focusing and diffusing the optical path, and an objective lens for focusing the laser beam onto the sample.

[0010] In one embodiment of the present invention, the imaging module includes a camera for observing the relative position of the laser transmitted from the optical excitation module and the sample, and the camera is electrically connected to the data collection and control module via a wire.

[0011] In one embodiment of the present invention, the fluorescence collection module includes a three-dimensional electric displacement stage for scanning NV color center counting. The fluorescence collection module also includes a reflector located on the side of the dichroic mirror away from the first lens and used to reflect fluorescence, a third lens and a fourth lens for focusing and diffusing the light path, and a single-photon detector for collecting and counting fluorescence, arranged sequentially along the fluorescence collection light path. The single-photon detector is electrically connected to the data collection and control module via a wire.

[0012] In one embodiment of the present invention, the diamond anvil cell includes a first diamond and a second diamond for applying pressure to the sample. NV color centers are injected into the anvil surface of the second diamond near the first diamond. An insulating pad is provided between the first diamond and the second diamond. A sample cavity for placing the sample is formed between the first diamond, the second diamond and the insulating pad. A platinum wire is provided in the sample cavity for transmitting microwaves and is in contact with the sample.

[0013] In one embodiment of the present invention, the low-temperature testing module includes a three-dimensional displacement stage, a thermostat disposed on the three-dimensional displacement stage, a low-temperature cavity disposed in the thermostat for placing a diamond anvil cell, and an in-situ pressure plate for applying pressure to the diamond anvil cell. The low-temperature testing module also includes a temperature controller connected to the low-temperature cavity, and a low-temperature semi-steel cable connected to the platinum wire and used for transmitting microwaves is disposed in the low-temperature cavity.

[0014] A high-sensitivity superconducting magnetic detection method based on NV centers under high pressure and low temperature, and based on the aforementioned high-sensitivity superconducting magnetic detection device based on NV centers under high pressure and low temperature, includes the following steps: correctly connecting each device in the microwave emission module, adjusting to the microwave sequence to be applied through the data collection and control module, correctly assembling the optical excitation module, imaging module, and fluorescence collection module, and debugging the data collection and control module to ensure the normal operation of the entire system; integrating the NV center onto the second diamond in the diamond anvil cell, aligning the two diamonds, then placing the insulating pad and the sample to be tested for superconducting properties in sequence, and placing platinum wires for transmitting microwaves on the sample;

[0015] A diamond anvil cell is placed in a cryogenic chamber, and the anvil cell and the cryogenic chamber are connected by a cryogenic semi-steel cable. The in-situ pressure plate is aligned with the diamond anvil cell. A magnetic field is applied through a magnet module. After adjusting the magnetic field to the target magnetic field, the temperature is changed by a temperature controller, and the pressure is changed by the in-situ pressure plate. Under the action of the microwave emission module, optical excitation module, imaging module, fluorescence collection module, and data collection and control module, the photodetector magnetic resonance spectrum of the sample at different temperatures is obtained. The superconducting transition temperature and pressure of the sample are obtained through the photodetector magnetic resonance spectrum.

[0016] As described above, the high-sensitivity superconducting magnetic detection device and method based on NV centers under high pressure and low temperature of the present invention has the following beneficial effects: The present invention injects NV centers into a diamond stage, and then integrates the diamond and NV centers onto a diamond anvil cell. Different stage sizes are used to provide different pressure environments. Insulating pads are used to place the sample, and platinum wire is used as the microwave transmission line. The present invention places the diamond anvil cell in a low-temperature cavity, and uses a low-temperature semi-steel cable to connect the diamond anvil cell and the low-temperature cavity. Compared with ordinary coaxial cables, the low-temperature semi-steel cable has less microwave transmission loss at low temperatures, thus obtaining better optical detection magnetic resonance spectrum signals, and thus obtaining more accurate superconducting transitions. The present invention replaces the ordinary low-temperature cavity sealing plate with a sealing plate that can be pressurized in situ, thus enabling in-situ pressurization at low temperatures, thereby achieving arbitrary pressure loading and unloading at any temperature, which is more in line with actual experimental requirements. The present invention replaces the ordinary diamond and ruby ​​pressure calibration with pressure calibration using the optical detection magnetic resonance spectrum of NV centers, which can achieve a more compact and convenient pressure calibration method, and the obtained local pressure is also more accurate. Attached Figure Description

[0017] Figure 1 The diagram shows the overall structural module of the high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature disclosed in the embodiments of the present invention.

[0018] Figure 2 The diagram shows the main component connections of the high-pressure, low-temperature, NV-center-based high-sensitivity superconducting magnetic detection device disclosed in this embodiment of the invention.

[0019] Figure 3 The diagram shows a diamond anvil cell in a high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature as disclosed in an embodiment of the present invention.

[0020] Figure 4 The diagram shows a diamond anvil cell and a cryogenic testing module in a high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature as disclosed in an embodiment of the present invention.

[0021] Figure 5 The diagram shows the overall flowchart of the high-sensitivity superconducting magnetic detection method based on NV color centers under high pressure and low temperature disclosed in the embodiments of the present invention.

[0022] Figure 6 The image shown is a schematic diagram of the optically detected magnetic resonance spectrum at 28K in the high-pressure, low-temperature, high-sensitivity superconducting magnetic detection method based on NV color centers disclosed in this embodiment of the invention.

[0023] Component designation explanation

[0024] 1. Microwave transmitting module; 101. Microwave source; 102. Microwave switch; 103. Power amplifier; 104. Load; 105. Circulator; 2. Optical excitation module; 201. Laser; 202. Dichroic mirror; 203. First lens; 204. Second lens; 205. Objective lens; 3. Imaging module; 301. Camera; 4. Fluorescence collection module; 401. Three-dimensional electric stage; 402. Mirror; 403. Third lens; 404. ... Four lenses; 405. Single-photon detector; 5. Data collection and control module; 6. Diamond anvil cell; 601. First diamond; 602. Second diamond; 603. NV color center; 604. Insulating gasket; 605. Sample; 606. Sample chamber; 607. Platinum wire; 7. Low-temperature testing module; 701. Three-dimensional displacement stage; 702. Thermostat; 703. Low-temperature semi-steel cable; 704. In-situ pressure plate; 705. Low-temperature chamber; 8. Magnet module. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0026] The first embodiment of the present invention relates to a highly sensitive superconducting magnetic detection device based on NV color centers under high pressure and low temperature. Please refer to [link to relevant documentation]. Figures 1 to 4 It includes a microwave emission module 1, an optical excitation module 2, an imaging module 3, a fluorescence collection module 4, a data collection and control module 5, a diamond anvil cell 6, a low-temperature testing module 7, and a magnet module 8.

[0027] Microwave transmitting module 1 generates microwaves of a specific frequency. By transmitting these microwaves to the diamond anvil cell 6, the spin state of the NV center 603 can be manipulated. Because the ground state of the NV center 603 is a spin triplet, the Zeeman effect causes further energy level splitting after an external static magnetic field is applied (the energy difference is proportional to the magnetic field strength). The microwave frequency needs to match the energy level difference between the two spin states, typically on the order of GHz. Microwaves are emitted through a frequency-tunable solid-state microwave generator—microwave source 101—and the microwave field is efficiently transmitted to the NV center 603, interacting with laser pulses (initialization / readout) and magnetic fields. With proper field coordination, pulse sequences can be achieved. The microwave transmitting module 1 includes a microwave source 101, a microwave switch 102, a power amplifier 103, a load 104, and a circulator 105, all electrically connected sequentially along the microwave transmission path via wires. The microwave source 101 is electrically connected to the data collection and control module 5 via wires. It should be noted that the microwave source 101 generates microwaves; the microwave switch 102 controls the switching of the microwaves; the power amplifier 103 amplifies the microwave signal power; the circulator 105 enables unidirectional signal transmission; and the load 104 prevents damage to the power amplifier 103.

[0028] Optical excitation module 2 is used to generate lasers to modulate the spin states of NV center 603, which can initialize NV center 603 and induce radiative transitions; continuous or pulsed 532nm lasers excite NV centers, and all spin states m s All were excited to the excited state, m s =±1 decays preferentially to m via ISC s =0, while m s =0 directly returns to the ground state. After multiple loops, the ground state is almost entirely concentrated in m. s =0 (polarizability > 90%), excited state 3 E's m s =0 returns to the ground state through a radiative transition (wavelength ~637-800nm), emitting red fluorescence; wherein, the optical excitation module 2 includes a laser 201, a dichroic mirror 202, a first lens 203, a second lens 204, and an objective lens 205 arranged sequentially along the laser emission path. It should be noted that the 532nm laser 201 is used to generate laser light to excite the sample 605; the dichroic mirror 202 is used to separate light into different wavelengths, so that light of different wavelengths propagates in different directions. In this invention, green light with a wavelength of 532nm is only reflected, while red light with a wavelength of 637nm is transmitted; the lens is used for focusing and diffusing the light path; the objective lens 205 is used to provide a magnified field of view and to focus the laser beam onto the sample 605.

[0029] Imaging module 3 is used to acquire the relative position information between the laser transmitted from optical excitation module 2 and sample 605, and feed it back to data collection and control module 5. Imaging module 3 includes camera 301 for observing the relative position between the laser transmitted from optical excitation module 2 and sample 605. Camera 301 is electrically connected to data collection and control module 5 through wires. It should be noted that observing the relative position between the laser transmitted from optical excitation module 2 and sample 605 through camera 301 and feeding it back to data collection and control module 5 means that camera 301 is focused on sample 605, and the position of the laser irradiating sample 605 is observed by the imaging software in data collection and control module 5 (hereinafter referred to as data collection and control module 5). The laser is adjusted to the required position by adjusting the three-dimensional displacement stage 701 under low temperature cavity 705 (hereinafter referred to as data collection and control module 5).

[0030] The fluorescence collection module 4 is used to collect relevant information generated in the diamond anvil cell 6 under the control of the microwave emission module 1 and the optical excitation module 2, and transmits the collected relevant information to the data collection and control module 5; excited state 3 E's m s =0 returns to the ground state via a radiative transition (wavelength ~637-800nm), emitting red fluorescence; m s The fluorescence intensity at 0 is significantly higher than that at m. s = ±1, therefore, contrast data in the optically detected magnetic resonance spectrum can be obtained: the typical fluorescence intensity difference is about 10-30%, which can be detected by the single-photon detector 405 or confocal microscope described below, and can be read out by the optically detected magnetic resonance spectrum; wherein, the fluorescence collection module 4 includes a three-dimensional electric displacement stage 401, and the fluorescence collection module 4 also includes a reflector 402, a third lens 403, a fourth lens 404 and a single-photon detector 405 arranged sequentially along the fluorescence collection optical path. The single-photon detector 405 is electrically connected to the data collection and control module 5 through wires. The fluorescence collection module 4 also includes a dichroic mirror 202, a first lens 203, a second lens 204, and an objective lens 205 shared with the optical excitation module 2. It should be noted that the three-dimensional electric displacement stage 401 is used to control the position of the objective lens 205 and to scan and count the NV color centers 603; the reflector 402 is used to reflect the light carrying information from the sample 605 to the single-photon detector 405 to obtain relevant information; the third lens 403 and the fourth lens 404 are used for focusing and diffusing the light path; and the single-photon detector 405 is used to collect and count the fluorescence.

[0031] The data collection and control module 5 controls the microwave emission module 1 to obtain the desired microwave sequence, and receives information from the imaging module 3 and the fluorescence collection module 4. Based on the information from the imaging module 3, it adjusts the relative position of the laser transmitted from the optical excitation module 2 with respect to the sample 605. Based on the information from the fluorescence collection module 4, it determines the photodetector magnetic resonance spectrum of the sample 605 at different temperatures. This data collection and control module 5 includes scanning software, imaging software, and spectral acquisition software. It should be noted that the fluorescence collection module 4 obtains the photodetector magnetic resonance spectrum, thereby obtaining information on contrast and peak positions. Furthermore, based on the linear relationship between the relative peak positions and pressure and magnetic field, it can deduce the pressure and magnetic field environment of the sample 605 in the DAC at that time. The imaging module 3 obtains the position information of the sample 605.

[0032] The diamond anvil cell 6 is used to place the sample 605 and generate a high-pressure environment. The anvil surface is composed of diamonds with injected NV color centers 603. In this invention, the NV color centers 603 are injected on the anvil surface of the second diamond 602 closest to the first diamond 601. In practical applications, it is only necessary to inject the NV color centers 603 on the anvil surface of one of the two diamonds. The optical excitation module 2 and the microwave emission module 1 directly control the NV color centers 603 to obtain relevant information, which is then transmitted to the imaging module 3 and the fluorescence collection module 4, and then to the data collection and control terminal to obtain data. The diamond anvil cell 6 includes a first diamond 601 and a second diamond 602, with a space between the first diamond 601 and the second diamond 602. An insulating spacer 604 forms a sample cavity 606 between the first diamond 601, the second diamond 602, and the insulating spacer 604. A platinum wire 607, in contact with the sample 605, is located within the sample cavity 606. It should be noted that the diamonds provide pressure to the two opposing diamonds, and NV color centers 603 are injected into the diamond anvils. The two diamonds are placed opposite each other and need to be properly aligned to avoid diamond loss. The insulating spacer 604 provides the sample cavity 606, holds the sample 605, and prevents conductivity with the platinum wire 607. The insulating spacer 604 is placed between the two diamonds. The sample 605 is the sample whose superconducting properties are to be tested. The NV color center 603 is integrated into the opposing anvils. The platinum wire 607 is used to transmit microwaves.

[0033] The low-temperature testing module 7 is used to place the diamond anvil 6 and provide low-temperature conditions. A low-temperature semi-steel cable 703 transmits the signal from the microwave transmitting module 1 to the diamond anvil 6. In-situ pressure plate 704 enables pressurization at low temperatures. The low-temperature testing module 7 includes a three-dimensional displacement stage 701, a thermostat 702 mounted on the three-dimensional displacement stage 701, a low-temperature chamber 705 within the thermostat 702, and an in-situ pressure plate 704. The low-temperature testing module 7 also includes a temperature controller. The low-temperature chamber 705 contains a low-temperature semi-steel cable 703 connected to the platinum wire 607. It should be noted that the three-dimensional displacement stage... 701 is used to adjust the relative position of sample 605 and laser; the cryogenic cavity 705 is used to provide a cryogenic environment, generally capable of providing temperatures up to the liquid helium temperature range, that is, temperatures as low as 4K; the cryogenic semi-steel cable 703 is used to transmit microwave signals. Compared with ordinary coaxial cables, this cryogenic cable is more suitable for cryogenic experiments, with less microwave loss, better NV light detection magnetic resonance spectrum peaks, and better signals; the temperature controller can control the temperature of sample 605 in DAC; the in-situ pressure plate 704 can pressurize the diamond anvil 6 at low temperatures, avoiding the repeated work of removing the press for pressurization, simplifying the process and saving time.

[0034] The magnet module 8 is used to apply a magnetic field to the diamond anvil cell 6; wherein the magnet module 8 includes a magnet that provides a magnetic field of different magnitudes to the sample chamber 606 in the cryogenic chamber 705.

[0035] The second embodiment of the present invention relates to a highly sensitive superconducting magnetic detection method based on NV color centers under high pressure and low temperature, the process of which is as follows: Figure 5 As shown, the specific steps include:

[0036] Step 101: Correctly connect the various devices in the microwave transmitting module 1, adjust to the desired microwave sequence through the data collection and control module 5, correctly build the optical excitation module 2, imaging module 3, and fluorescence collection module 4, and debug the data collection and control module 5 to ensure the normal operation of the entire system.

[0037] Step 102: Integrate the NV color center 603 onto the second diamond 602 in the diamond anvil cell 6, then center the two diamonds, and then place the insulating pad 604 and the sample 605 to be tested for superconductivity in sequence, and place the platinum wire 607 for transmitting microwaves on the sample 605.

[0038] Step 103: Place the diamond anvil 6 into the cryogenic chamber 705, connect the diamond anvil 6 and the cryogenic chamber 705 with a cryogenic semi-steel cable 703, and align the in-situ pressure plate 704 with the diamond anvil 6.

[0039] Step 104: Apply a magnetic field through the magnet module 8, adjust the magnetic field size to the target magnetic field, change the temperature through the temperature controller, change the pressure through the in-situ pressure plate 704, and obtain the photodetector magnetic resonance spectrum of sample 605 at different temperatures under the action of microwave emission module 1, optical excitation module 2, imaging module 3, fluorescence collection module 4, and data collection and control module 5. Obtain the superconducting transition temperature and pressure of sample 605 through the photodetector magnetic resonance spectrum.

[0040] Specifically, before conducting the low-temperature, high-pressure superconducting detection example, it is necessary to... Figure 1 The eight structural modules need to be assembled and adjusted, including the microwave emission module 1, the optical excitation module 2, and the data collection and control module.

[0041] First, the microwave transmitting module 1 needs to be constructed according to the microwave section of the optical detection magnetic resonance system. Different microwave sources 101 can output microwave signals of different frequencies. The microwave signals pass through the microwave switch 102, power amplifier 103, load 104, and circulator 105, and are finally transmitted to the platinum wire 607 in the diamond anvil cell 6 through the low-temperature semi-steel cable 703, where the emitted microwaves act on the NV color center 603. The optical excitation module 2 emits laser light from the 532nm laser 201, which passes through the dichroic mirror 202, lens, and objective lens 205 before being focused onto the sample 605.

[0042] Imaging module 3 mainly transmits images from camera 301 to data collection and control module 5, and adjusts the position of the displacement stage of cryogenic cavity 705 by observing the imaging. Fluorescence collection module 4 collects the fluorescence emitted by the color center, which enters the single-photon detector 405 after passing through dichroic mirror 202, reflector 402 and lens. Single-photon detector 405 collects and processes the signal, which is reflected in the spectrum in the software of data collection and control module 5. Data collection and control module 5 mainly includes imaging, scanning and testing software. It first confirms the relative position of sample 605 and laser before scanning, and finally selects the NV color center 603 point to collect the photodetector magnetic resonance spectrum.

[0043] First, the NV color center 603 in the diamond needs to be injected into the diamond anvil 6. The NV color center 603 is integrated into the diamond anvil 6. Then, the two diamonds are aligned, spacers are pressed, insulation is done, and the sample 605 and platinum wire 607 are placed. Then, the diamond anvil 6 is placed in the low temperature chamber 705. The diamond anvil 6 and the low temperature chamber 705 are connected by a low temperature semi-steel cable 703. The in-situ pressure plate 704 is aligned with the diamond anvil 6, and the entire chamber is sealed. The magnet module 8 is placed and the magnet is directly opposite the diamond anvil 6 to ensure the uniformity of the magnetic field.

[0044] After the experimental setup is installed, the cooling process can begin. Once the target temperature is reached, the imaging module 3 and laser 201 are activated. The relative positions of the laser and sample 605 in the DAC are confirmed, and scanning is performed. A selected point is scanned using optically detected magnetic resonance (ODMR) to determine the peak position. The real-time pressure value is obtained using the relationship between the D value in the ODMR spectrum of the NV color center 603 and the pressure. Pressure is then applied using the in-situ pressure plate 704, and the position of the D value is observed to confirm the applied pressure value until the target pressure is reached. This operation avoids the use of diamond and ruby ​​pressure standards. The magnitude of the magnetic field is determined using the magnet module 8, and the actual magnetic field magnitude of sample 605 is confirmed based on the E value in the ODMR spectrum.

[0045] Measurement Procedure: After cooling to the minimum temperature under the target pressure, a target magnetic field is applied, and the photodetector magnetic resonance spectrum is measured. The temperature is then gradually increased, and the photodetector magnetic resonance spectrum is measured at different temperatures. The superconducting transition temperature of the material at that pressure is confirmed by the change in the E value in the photodetector magnetic resonance spectrum. For details, please refer to [link to relevant documentation]. Figure 6 , Figure 6 The image shows the optically detected magnetic resonance spectrum at 28 K. From this image, we can obtain that the pressure is 30.5 GPa and the magnetic field is 21.7 Gs.

[0046] In summary, this invention discloses a method for measuring the superconducting transition of materials under low-temperature and high-pressure conditions by measuring photodetector magnetic resonance spectroscopy based on NV centers implanted on the anvil surface of a diamond anvil cell. The method uses a diamond anvil cell (NV center 603) as the anvil of a DAC module, simultaneously achieving high-pressure and low-temperature conditions in liquid helium and liquid nitrogen temperature ranges. Photodetector magnetic resonance spectroscopy measures the superconducting transition of sample 605 under different pressures and temperatures. This method can achieve in-situ pressure measurement under high pressure, has no impact on sample 605 compared to conventional methods, and does not require ruby ​​or Raman pressure calibration. Sample 605 is placed in a diamond anvil cell 6, which is then placed in a low-temperature chamber 705. A minimum temperature of 4K and in-situ pressurization can be achieved using a low-temperature testing module 7. Microwave transmission is achieved using a low-temperature semi-steel cable 703, which, compared to other types of coaxial cables, offers higher quality microwave signal transmission with less loss. This allows for quantitative testing of the superconducting properties of materials under low-temperature and high-pressure conditions in a highly integrated manner.

[0047] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature, characterized in that: It includes a microwave emission module (1), an optical excitation module (2), an imaging module (3), a fluorescence collection module (4), a data collection and control module (5), a diamond anvil cell (6), a low-temperature testing module (7), and a magnet module (8); The microwave transmitting module (1) is used to generate microwaves of a specific frequency. By transmitting the microwaves of the specific frequency to the diamond anvil cell (6), the spin state of the NV color center (603) can be manipulated. The optical excitation module (2) is used to generate lasers to regulate the spin state of the NV color center (603), which can initialize the NV color center (603) and generate radiative transitions. The imaging module (3) is used to collect the relative position information of the laser transmitted from the optical excitation module (2) and the sample (605), and feed it back to the data collection and control module (5); the fluorescence collection module (4) is used to collect the relevant information generated in the diamond anvil cell (6) under the control of the microwave emission module (1) and the optical excitation module (2), and transmit the collected relevant information to the data collection and control module (5); The data collection and control module (5) is used to control the microwave emission module (1), and receive information sent by the imaging module (3) and the fluorescence collection module (4). According to the information sent by the imaging module (3), it adjusts the relative position of the laser transmitted by the optical excitation module (2) and the sample (605). According to the information sent by the fluorescence collection module (4), it determines the photodetector magnetic resonance spectrum of the sample (605) at different temperatures. The diamond anvil cell (6) is used to place the sample (605) and generate a high-pressure environment; the low-temperature testing module (7) is used to place the diamond anvil cell (6) and provide low-temperature conditions, and can transmit the microwave signal of the microwave transmitting module (1) to the diamond anvil cell (6); the magnet module (8) is used to apply a magnetic field to the diamond anvil cell (6).

2. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 1, characterized in that: The microwave transmitting module (1) includes a microwave source (101) for generating microwaves, a microwave switch (102) for controlling the microwave switch, a power amplifier (103) for amplifying the microwave signal power, a load (104) for preventing damage to the amplifier, and a circulator (105) for realizing unidirectional signal transmission, all connected in sequence along the microwave transmission path by wires. The microwave source (101) is electrically connected to the data collection and control module (5) by wires.

3. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 1, characterized in that: The optical excitation module (2) includes a laser (201) for generating laser light, arranged sequentially along the laser emission light path, a dichroic mirror (202) for separating light into different wavelengths and propagating in different directions, a first lens (203) and a second lens (204) for focusing and diffusing the light path, and an objective lens (205) for focusing the laser beam onto the sample (605).

4. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 1, characterized in that: The imaging module (3) includes a camera (301) for observing the relative position of the laser transmitted from the optical excitation module (2) and the sample (605), and the camera (301) is electrically connected to the data collection and control module (5) via a wire.

5. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 3, characterized in that: The fluorescence collection module (4) includes a three-dimensional electric displacement stage (401) for scanning and counting NV color centers (603). The fluorescence collection module (4) also includes a reflector (402) arranged sequentially along the fluorescence collection optical path, located on the side of the dichroic mirror (202) away from the first lens (203) and used for reflecting fluorescence; a third lens (403) and a fourth lens (404) for focusing and diffusing the optical path; and a single-photon detector (405) for collecting and counting fluorescence. The single-photon detector (405) is electrically connected to the data collection and control module (5) via a wire.

6. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 1, characterized in that: The diamond anvil cell (6) includes a first diamond (601) and a second diamond (602) for applying pressure to the sample (605). NV color centers (603) are injected into the anvil surface of the second diamond (602) near the first diamond (601). An insulating gasket (604) is provided between the first diamond (601) and the second diamond (602). A sample cavity (606) for placing the sample (605) is formed between the first diamond (601), the second diamond (602), and the insulating gasket (604). A platinum wire (607) is provided in the sample cavity (606) for transmitting microwaves and is in contact with the sample (605).

7. The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature according to claim 6, characterized in that: The low-temperature testing module (7) includes a three-dimensional displacement stage (701), a thermostat (702) disposed on the three-dimensional displacement stage (701), a low-temperature chamber (705) disposed in the thermostat (702) for placing a diamond anvil (6), and an in-situ pressure plate (704) for applying pressure to the diamond anvil (6). The low-temperature testing module (7) also includes a temperature controller connected to the low-temperature chamber (705). The low-temperature chamber (705) is provided with a low-temperature semi-steel cable (703) connected to the platinum wire (607) for transmitting microwaves.

8. A high-sensitivity superconducting magnetic detection method based on NV color centers under high pressure and low temperature, characterized in that: The high-sensitivity superconducting magnetic detection device based on NV color centers under high pressure and low temperature as described in any one of claims 1-7 includes the following steps: After correctly connecting the various devices in the microwave transmitting module (1) and adjusting them to the microwave sequence to be applied through the data collection and control module (5), the optical excitation module (2), imaging module (3) and fluorescence collection module (4) are correctly assembled, and the data collection and control module (5) is debugged to ensure the normal operation of the entire system. The NV color center (603) is integrated onto the second diamond (602) in the diamond anvil cell (6), and the two diamonds are then aligned. Then, an insulating pad (604) and a sample (605) to be tested for superconductivity are placed in sequence, and a platinum wire (607) for transmitting microwaves is laid on the sample (605). Place the diamond anvil (6) into the cryogenic chamber (705), connect the diamond anvil (6) and the cryogenic chamber (705) with a cryogenic semi-steel cable (703), and align the in-situ pressure plate (704) with the diamond anvil (6); A magnetic field is applied by the magnet module (8), and the magnetic field size is adjusted to the target magnetic field. The temperature is changed by the temperature controller, and the pressure is changed by the in-situ pressure plate (704). Under the action of the microwave emission module (1), optical excitation module (2), imaging module (3), fluorescence collection module (4), and data collection and control module (5), the photodetector magnetic resonance spectrum of the sample (605) at different temperatures is obtained. The superconducting transition temperature and pressure of the sample (605) are obtained by the photodetector magnetic resonance spectrum.

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