Electrical measurement sample rod in extreme environment based on microwave radio frequency rectification and application of electrical measurement sample rod

Abstract

The invention discloses an electrical measurement sample rod in an extreme environment based on microwave radio frequency rectification and application of the electrical measurement sample rod in the extreme environment, the sample rod is combined with a comprehensive physical property measurement system PPMS to integrate research of nonlinear rectification at normal temperature in the PPMS in the extreme environment, measurement in a high-intensity magnetic field from low temperature to 2K and 9T is realized, and the test is more sensitive; a customized transmitting antenna and a receiving antenna are integrated on a sample rod, microwaves with different frequencies are applied, the test frequency is set to be 600 MHz to 6000 MHz, a tested radio frequency rectified signal mainly comes from a topological electronic state, and a good test means is provided for researching the intrinsic physical property of a topological quantum material; compared with a sample rod of a PPMS system, due to the good thermal design, a thermometer of the PPMS system can represent the temperature of the sample, cost is greatly reduced, operation is easy, measuring means are diversified, and multiple samples can be measured at the same time.

Description

Technical Field

[0001] This invention relates to a sample holder for carrying a sample to be tested, and more particularly to a sample holder for measuring the intrinsic properties of topological quantum materials under microwave radio frequency rectification. Background Technology

[0002] Radio frequency (RF) rectification, also known as nonlinear rectification, refers to the physical process of directly converting alternating current or an alternating electric field without bias into a directional direct current by utilizing the nonlinear transport properties of materials. This is achieved by measuring the Hall effect at both ends. Its core difference lies in traditional semiconductor PN junction rectification, which relies on the asymmetry of carrier transport in the barrier region. RF rectification does not require a heterojunction structure; it achieves rectification solely through the material's own symmetry breaking, topological properties, geometric properties, or disorder. It offers advantages such as low power consumption, wide-band response, and simple structure. The physical essence of nonlinear rectification is the second-order nonlinear transport response of the material to an alternating electric field. Its core mechanism is deeply related to the intrinsic physical roots of the nonlinear Hall effect, and is mainly divided into intrinsic and extrinsic types. The intrinsic mechanism is centered on the Berry curvature dipole, which is dominated by geometric properties: when an alternating electric field acts on the material, the Berry curvature dipole induces a transverse second-order current response, the direction of which is determined by the spatial distribution characteristics of the Berry curvature, ultimately exhibiting a "unidirectional transport" rectification effect. Intrinsic mechanisms are closely related to disordered states in materials and sample defects, specifically including two sub-mechanisms: oblique scattering and side-jump scattering. Oblique scattering is dominant at higher temperatures, while the contribution of side-jump scattering depends on temperature scaling parameters at low temperatures.

[0003] Current research on nonlinear rectification has propelled the exploration of novel topological properties of topological quantum materials into the realm of nonlinear responses, opening up richer and more interesting areas for future research in this direction. Simultaneously, the core concept of the nonlinear Hall effect has spurred numerous unique physical phenomena that have been theoretically proposed and experimentally verified, laying a crucial foundation for the mechanism innovation and application exploration of nonlinear rectification. An important frontier research direction will be to gain a deeper understanding of the underlying mechanisms of the nonlinear Hall effect and further explore its potential applications. Generally, nonlinear rectification tests are conducted at room temperature. By studying the power of its rectification effect, the potential application value of the material's rectification effect can be evaluated, or multiple electrode Hall structures can be fabricated to study the underlying physical mechanism of the nonlinear Hall effect. However, external fields, such as temperature and magnetic fields, have a significant modulating effect on material properties. Therefore, measuring samples under low-temperature, high-magnetic-field conditions helps to more comprehensively understand the nonlinear transport effects of topological materials. The Power Proportional Measurement System (PPMS), developed by Quantum Design in the United States, is an instrument for studying the physical properties of materials, possessing a low-temperature and high-magnetic-field measurement environment, as well as strong scalability. By utilizing the low-temperature, high-magnetic-field environment of this system to study the nonlinear rectification effect of topological materials and evaluate its potential application in radio frequency rectification, we can advance the further development and application of the nonlinear rectification effect. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to study the intrinsic properties of topological quantum materials and to provide a sample rod for testing their intrinsic properties in a microwave radio frequency rectification environment; another purpose of this invention is to provide its application in the intrinsic property testing of topological quantum materials.

[0005] Technical Solution: The present invention relates to an electrical measurement sample rod based on microwave radio frequency rectification under extreme environments, comprising an adapter and a sample holder base, which are fixedly connected by a connecting rod; the adapter includes an adapter for connecting a measuring instrument and a microwave emission source; the sample holder base is a hollow structure, with a sample holder and a transmitting antenna disposed inside; the adapter for the measuring instrument on the adapter is electrically connected to the sample holder on the sample holder base, and the adapter for the microwave emission source on the adapter is electrically connected to the transmitting antenna on the sample holder base; multiple heat-resistant rings are fitted on the connecting rod, with the inner wall of the heat-resistant rings tightly attached to the connecting rod and the outer wall tightly attached to the sample chamber of the testing instrument, dividing the sample chamber into different temperature zones.

[0006] Furthermore, the heat-resistant ring is wrapped with a heat-conducting ring, which has a double-layer structure. The inner layer is tightly fitted to the heat-resistant ring, and the outer layer is a strip structure arranged circumferentially around the inner layer. The heat-resistant ring is made of aluminum alloy, and the heat-conducting ring is made of copper alloy, preferably beryllium copper spring sheet. The strip structure arranged circumferentially on the outer layer of the beryllium copper spring sheet has a certain elastic diameter change function to ensure that the heat-conducting ring is always in contact with the inner wall of the PPMS sample chamber during thermal expansion and contraction, thereby improving thermal connection.

[0007] Furthermore, the adapter also includes an oscilloscope adapter and a receiving antenna inside the sample holder, which are electrically connected to facilitate monitoring of changes and fluctuations in the transmitted microwave.

[0008] Furthermore, the transmitting and receiving antennas are patch-type structures, their size matching the narrow operating range of PPMS, with an operating frequency of 600MHz to 6000MHz. Theoretically, a wider microwave frequency range can be further achieved through the design of the transmitting antenna. The patch antenna can be customized as needed; there are no special requirements for its internal structure. Its preferred dimensions are 34mm*12mm and a thickness of 2mm. The back of the antenna can be easily attached to the inner wall of the sample holder using adhesive. The transmitting and receiving antennas can be arranged adjacent to each other or on opposite sides of the sample holder; the closer they are to the sample, the more accurate the test results.

[0009] Furthermore, the adapter is a three-dimensional hollow structure with circular or square openings on its side walls. A blind plate is sealed over these openings, and the adapters for the measuring instruments, microwave transmitter, and oscilloscope pass through the blind plate and are fixedly connected to its outer side. The bottom of the adapter has a slot that connects to the upper end of the connecting rod via a connecting flange, and also includes clearance holes to facilitate the passage of connecting wires for electrical connection at both ends. A flange at the bottom of the adapter mates with the sample chamber of the PPMS system, achieving a sealed connection between the sample rod and the PPMS system sample chamber.

[0010] Furthermore, the heat-resistant ring is provided with clearance holes to facilitate the passage of wires. The connecting wire passes through the heat-resistant ring and the heat-conducting ring and is wound around the connecting rod, or the measuring wire and the RF coaxial cable pass through the connecting rod and connect to the two ends of the interface. It is preferable to wrap the measuring wire and the RF coaxial cable around the connecting rod. On the one hand, this facilitates the fixation of the wires and prevents the wires from shaking at low temperatures, which would affect signal measurement. On the other hand, considering that the wires generate heat when current is applied and that all wires are connected to the instrument through the adapter and exposed to the air, when the sample cavity reaches a certain low temperature, the insulation layer of the external Remo connector and the conductive copper core of the SMA RF interface will leak heat into the sample cavity, causing the sample cavity temperature to rise. Wrapping the wires around the connecting rod can quickly conduct heat to the sample cavity, acting as a heat sink.

[0011] Furthermore, the sample holder base is a hollow cylindrical structure. The sample holder is located in the middle of the hollow cylindrical structure, and the transmitting and receiving antennas are set on the inner wall of the hollow cylindrical structure. Thermally conductive rings are fitted onto the outer walls of the upper and lower ends of the hollow cylindrical structure. These thermally conductive rings are in contact with the sample cavity wall, facilitating thermal bonding, accelerating the cooling of the sample on the sample holder, and simultaneously suppressing the thermal effect brought by the radio frequency antenna, ensuring the system temperature is maintained. The sample holder base is made of oxygen-free copper, which has good thermal conductivity and is non-magnetic, facilitating heat sinking.

[0012] Furthermore, the sample holder includes multiple horizontally and / or vertically arranged samples to meet the measurement needs of multiple samples or different directions; the bottom of the sample holder is provided with multiple pins for connecting the sample to the measuring leads, which facilitates the connection of the sample to be tested to the measuring leads.

[0013] Furthermore, the connecting rod has a hollow structure with vent holes. After the sample rod is placed, the PPMS system performs a vacuum evacuation to remove the air inside the connecting rod, maintaining the same vacuum level as the PPMS system and preventing air from affecting the temperature drop of the sample rod. The connecting rod is preferably made of aluminum alloy with an outer diameter of 8mm and an inner diameter of 6mm, providing a certain load-bearing capacity. At least four sets of heat-resistant and heat-conducting rings are fitted onto the connecting rod. When the sample rod is placed in the PPMS sample chamber, the heat-conducting rings contact the inner wall of the PPMS sample chamber. The heat-resistant and heat-conducting rings work together to divide the sample chamber into multiple temperature zones, while simultaneously preventing temperature fluctuations in the sample chamber caused by the vertical convection of helium gas.

[0014] Furthermore, the adapter of the measuring instrument on the adapter section is connected to one or more instruments for testing voltage, current or resistance, for studying the different electrical properties of the material under the test environment.

[0015] This invention also provides the application of the above-mentioned microwave radio frequency rectification-based electrical measurement sample rod in extreme environments for intrinsic property testing of topological quantum materials, which can be used to study the transport properties of materials in condensed matter physics.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0017] 1. This invention creatively integrates the study of nonlinear rectification at room temperature into a comprehensive physical property measurement system (PPMS) for extreme environments, enabling measurements at temperatures down to 2K and in strong magnetic fields up to 9T. The testing technology provided by this invention can more sensitively determine abnormal resistance peaks (voltage values ​​changing from negative to positive near 128K), provides clearer and more intuitive visualization of microwave radio frequency signal-induced oscillations under magnetic fields, and more clearly demonstrates the Zeeman splitting effect of the sample. This is crucial for measuring minute signals indicating changes in the electronic states of materials and has significant application potential.

[0018] 2. Applying the study of nonlinear rectification at room temperature to a low-temperature, high-magnetic-field environment, microwave radio frequency measurements under magnetic fields are more sensitive to phase transitions. In topological materials and space-broken material systems, the contribution of the nontrivial electron-hole band is often masked by the contributions of electrons and holes in other bands. Theoretically, the RF rectified signal tested in this invention is mainly contributed by Berry curvature, i.e., mainly by nontrivial electronic states, with other electronic states contributing very little. This provides an excellent testing method for studying the intrinsic properties of topological materials.

[0019] 3. By integrating a custom-designed transmitting and receiving antenna onto the sample rod, the fundamental physical properties of the sample under low-temperature, high-magnetic-field conditions can be studied at a low cost. Compared to the sample rods of PPMS systems, which often cost tens of thousands of yuan, this invention can perform not only ordinary electrical transport measurements but also microwave and radio frequency measurements at low temperatures. The custom-designed transmitting and receiving antennas are cost-effective, and the most expensive component on the sample rod, the thermometer, can be replaced by the thermometer integrated into the PPMS system due to its excellent thermal design, significantly reducing costs.

[0020] 4. By integrating a custom-designed transmitting and receiving antenna onto the sample rod, and applying microwaves of different frequencies, the DC response is measured. This method offers a wide testing frequency range, from 600MHz to 6000MHz, and is simple to operate. Compared to ordinary electrical measurements, the system only requires a microwave transmitter and a DC meter, resulting in a simpler system. However, it offers high testing accuracy. The measurement methods are diverse, and several samples can be measured simultaneously, further improving research efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a cross-sectional view of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the adapter of the present invention;

[0024] Figure 4 This is a schematic diagram of the sample holder base of the present invention;

[0025] Figure 5 This is a schematic diagram of the structure of the heat-conducting ring and the heat-resistant ring of the present invention;

[0026] Figure 6 The graph shows the resistance measurement results of the ZrTe5 crystal under normal conditions and the voltage change measured under the applied RF microwave signal of 2160MHz in this embodiment.

[0027] Figure 7The graphs show the resistive oscillations of a ZrTe5 crystal at 2K and the voltage oscillations measured under an applied RF microwave signal of 2160MHz. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0029] Example 1

[0030] like Figure 1-2 The diagram illustrates an electrical measurement sample rod for extreme environments based on microwave radio frequency rectification. It includes an adapter 1 and a sample holder 3. The upper end of the connecting rod 2 is connected to a slot below the adapter 1, and the lower end is fixedly connected to the sample holder 3. (Example:) Figure 3 As shown, the adapter 1 is a three-dimensional hollow structure with a circular opening on its side wall. A blind plate 12 is sealed and connected to the circular opening. The adapter 11 of the voltage measuring instrument and the adapter 13 of the microwave emission source pass through the blind plate 12 and are fixedly connected to the outside of the blind plate 12. The bottom of the adapter 1 is provided with a slot and is fixedly connected to the upper end of the connecting rod 2 through a connecting flange. At the same time, a wire avoidance hole is provided. Figure 4 As shown, the sample holder base 3 is a hollow cylindrical structure made of oxygen-free copper. The sample holder 31 is located in the middle of the hollow cylindrical structure. The transmitting antenna 32 is set on the inner wall of the hollow cylindrical structure. The upper and lower outer walls of the hollow cylindrical structure are fitted with heat-conducting rings 24, which are in contact with the sample cavity wall. The transmitting antenna 32 is a patch structure, and its size matches the narrow working range of PPMS (PPMS sample cavity diameter 26mm). The working frequency is 600MHz to 6000MHz. The sample holder 31 includes two horizontal and two vertical ones. Each sample holder 31 has eight pins at the bottom, which can fix 2 to 4 samples for simultaneous testing. The voltage measuring instrument adapter 11 on the adapter section 1 uses a Remo connector to connect to a Keithley 2182A nanovoltmeter, and is connected to the pin on the bottom of the sample tray 31 on the sample tray base 3 via the measuring lead 22; the microwave transmitter adapter 13 on the adapter section 1 uses an SMA RF interface, and is connected to the transmitting antenna 32 on the sample tray base 3 via the RF coaxial cable 21; Figure 5 As shown, four sets of heat-resistant rings are fitted onto the connecting rod 2. The heat-resistant rings 23 are made of aluminum alloy and are preferably two-stage reducing tubes. The smaller diameter tube is fitted onto the outer wall of the connecting rod 2, and the larger diameter tube is in close contact with the inner wall of the sample chamber. The heat-resistant rings 23 divide the sample chamber into multiple temperature zones. The connecting rod 2 is a hollow stainless steel tube with three vent holes. The heat-resistant rings 23 have clearance holes to facilitate the passage of wires. The measuring wires 22 are made of braided copper wires. The measuring wires 22 and the RF coaxial cable 21 pass through the clearance holes on the heat-resistant rings 23 and are wound around the connecting rod 2. They also pass through the clearance holes at the bottom of the adapter 1 to achieve connection at both ends. The bottom of the adapter 1 has a KF40 flange for docking with the sample chamber of the PPMS system.

[0031] Example 2

[0032] Unlike Example 1, the heat-insulating ring 23 is also wrapped with a heat-conducting ring 24. The heat-conducting ring 24 has a double-layer structure, with its inner layer tightly attached to the heat-insulating ring 23 and its outer layer being a strip structure arranged circumferentially around the inner layer. It is preferably made of beryllium copper spring sheet. The strip structure arranged circumferentially on the outer layer of the beryllium copper spring sheet has a certain elastic diameter change function to ensure that the heat-conducting ring 24 is always in contact with the inner wall of the PPMS sample chamber during thermal expansion and contraction. The outer wall of the large-diameter heat-insulating ring 23 is inserted into the middle of the double-layer structure of the heat-conducting ring 24 and fixed with a small amount of epoxy resin to prevent it from falling off when inserting or removing the sample rod. The heat-insulating ring 23 and the heat-conducting ring 24 work together to successfully divide the sample chamber into multiple temperature zones.

[0033] Compared with Examples 1 and 2, the heat-insulating ring 23 is wrapped with a heat-conducting ring 24. The strip structure set in the outer circumference of the beryllium copper spring sheet has a certain elastic diameter change function, ensuring that the heat-conducting ring 24 is always in contact with the inner wall of the PPMS sample chamber when thermally expanding and contracting, blocking convection between different temperature zones while improving the thermal connection between the PPMS sample chamber and the sample rod.

[0034] Example 3

[0035] Unlike Example 1, as Figure 3 As shown, an oscilloscope adapter is also installed on the side wall of the adapter section 1, and a receiving antenna 33 is installed on the inner wall of the sample holder 3. The oscilloscope adapter also uses an SMA RF interface and is connected to the receiving antenna 33 on the sample holder 3 via another RF coaxial cable 21. The receiving antenna 33, like the transmitting antenna 32, is a patch structure. Its size matches the narrow working range of the PPMS (PPMS sample cavity diameter 26mm), and its operating frequency is 600MHz to 6000MHz. The two antennas are located on the inner wall of the sample holder 3 and on both sides of the sample holder 3. The measuring lead 22 and the two RF coaxial cables 21 pass through the clearance holes on the heat shield ring 23 and are wound around the connecting rod 2. By setting up an oscilloscope, the fluctuation of the microwave signal during the test can be monitored to ensure the accuracy of the test.

[0036] Example 4

[0037] Unlike Embodiment 1, the adapter on the adapter section 1 connects to multiple instruments for voltage, current, or resistance. The adapter type is selected to match the test instrument; for example, a Remo interface adapter is used for current testing to connect to a Keithley 2400 / 2450 digital source meter, and an aviation plug adapter is used for resistance testing to connect to a Keithley 6221 source meter and a lock-in amplifier SR830 / 865. By setting different test instruments, different electrical performance characteristics under extreme microwave RF rectification conditions can be tested.

[0038] In use, the sample to be tested is placed on the sample holder 31, and the sample is connected to the measuring lead 22 via the pin provided. Then, the sample rod of this embodiment is inserted into the PPMS sample chamber. At this time, the upper and lower ends of the cylindrical hollow structure of the sample holder base 3 are equipped with heat-conducting rings that contact the sample chamber wall of the PPMS integrated physical property measurement system, thereby ensuring a tight connection and improving thermal connection. The bottom of the adapter 1 is connected to the vacuum flange on the sample chamber via a KF40 flange to achieve sample chamber sealing. During normal sample chamber cooling, due to thermal expansion and contraction, the entire sample rod will partially shrink. The designed multiple sets of heat-insulating rings 23 and heat-conducting rings 24 successfully divide the upper and lower temperature zones of the sample rod, preventing vertical convection. At the same time, the heat-conducting rings 24 on the upper and lower parts of the sample holder base 3 further expand the contact with the bottom of the PPMS sample chamber. Since there is a constant temperature zone at the bottom of the PPMS sample chamber, the bottom of the sample holder 31 contacts the sample chamber from top to bottom, resulting in better heat conduction and cooling, reducing the temperature difference between the upper and lower parts of the sample holder, and improving the accuracy of the measurement. Figure 6 The graph shows the resistance measurement results of a ZrTe5 crystal under normal conditions and the voltage change measured under a 2160 MHz radio frequency microwave signal applied in this embodiment. A comparison reveals that the testing technique provided by this invention can more sensitively detect abnormal resistance peaks (voltage values ​​near 128K changing from negative to positive). Figure 7 The resistive oscillations of ZrTe5 crystal at 2K and the voltage oscillations measured under a 2160MHz radio frequency microwave signal clearly show that the oscillations of the microwave radio frequency signal under a magnetic field are more distinct and intuitive, and the Zeeman splitting effect of the sample is more pronounced. This indicates that the electrical measurement technology based on microwave radio frequency rectification under extreme environments provided by this invention is highly sensitive to the measurement of minute signals of changes in the electronic state of materials, and has significant application potential.

[0039] The present invention has been described in detail herein using general descriptions, specific embodiments, and experiments. However, modifications or improvements can be easily made to the present invention by those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention. The scope of the present invention is defined by the appended claims rather than the foregoing description, and is intended to encompass all variations falling within the meaning and scope of equivalents of the claims. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification, comprising an adapter (1) and a sample holder (3), the two being fixedly connected by a connecting rod (2); characterized in that, The adapter (1) includes an adapter for connecting the measuring instrument and the microwave emission source; the sample holder base (3) is a hollow structure, with a sample holder (31) and a transmitting antenna (32) inside; the adapter of the measuring instrument on the adapter (1) is electrically connected to the sample holder (31) on the sample holder base (3), and the adapter of the microwave emission source on the adapter (1) is electrically connected to the transmitting antenna (32) on the sample holder base (3); multiple heat-insulating rings (23) are sleeved on the connecting rod (2), and the inner wall of the heat-insulating ring (23) is tightly attached to the connecting rod (2), and the outer wall is tightly attached to the sample chamber of the testing instrument, dividing the sample chamber into different temperature zones.

2. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 1, characterized in that, The heat-insulating ring (23) is wrapped with a heat-conducting ring (24). The heat-conducting ring (24) has a double-layer structure, with the inner layer tightly attached to the heat-insulating ring (23) and the outer layer being a strip structure arranged around the inner layer. The heat-insulating ring (23) is made of aluminum alloy and has clearance holes for easy passage of wires. The heat-conducting ring (24) is made of copper alloy.

3. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 1, characterized in that, The adapter (1) also includes an oscilloscope adapter and a sample holder (3) with a receiving antenna (33) inside, which are electrically connected.

4. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 3, characterized in that, The transmitting antenna (32) and receiving antenna (33) are patch-type structures, and their size matches the narrow operating range of the PPMS integrated physical property measurement system, with an operating frequency of 600MHz to 6000MHz.

5. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 3, characterized in that, The adapter (1) is a three-dimensional hollow structure with a circular or square opening on its side wall. A blind plate (12) is sealed and connected to the opening. The adapter of the measuring instrument and the microwave emission source and the oscilloscope are fixedly connected to the outside of the blind plate (12) through the blind plate (12). A flange is provided at the bottom of the adapter (1) to dock with the sample chamber of the PPMS system.

6. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 3, characterized in that, The sample holder base (3) is a hollow cylindrical structure. The sample holder (31) is located in the middle of the hollow cylindrical structure. The transmitting antenna (32) and the receiving antenna (33) are set on the inner wall of the hollow cylindrical structure. The upper and lower outer walls of the hollow cylindrical structure are fitted with heat-conducting rings (24).

7. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 1 or 6, characterized in that, The sample holder (31) includes multiple samples arranged horizontally and / or vertically; the bottom of the sample holder (31) is provided with multiple pins for connecting to the sample.

8. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 1, characterized in that, The connecting rod (2) is a hollow structure with ventilation holes.

9. The sample rod for electrical measurement under extreme environments based on microwave radio frequency rectification according to claim 1, characterized in that, The adapter of the measuring instrument on the adapter (1) is connected to one or more instruments for testing voltage, current or resistance.

10. The application of the microwave radio frequency rectification-based electrical measurement sample rod under extreme conditions as described in claim 1 in the intrinsic property testing of topological quantum materials.

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