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Coherent manipulation of multiple ions in a room-temperature surface-electrode trap
XIE Yi, CHEN Ting, WANG Hongyang, TAO Yi, ZHANG Xin, CHEN Yan, ZHANG Jie, WU Wei, CHEN Pingxing
Abstract +
The development of high-performance chip-scale ion traps is pivotal for the integration and scaling of ion-trap-based quantum computers. While cryogenic environments can significantly suppress anomalous heating, operating ion traps at room temperature remains highly attractive for its simplicity and lower cost. This work reports significant progress in coherently controlling multiple ions confined in a custom-fabricated, room-temperature surface-electrode trap, establishing a critical foundation for advanced quantum protocols like quantum error correction and future scalable architectures. Research Objectives and Methods Our study aimed to characterize a home-built chip trap and demonstrate its capabilities for multi-ion quantum logic under ambient conditions. The trap features a six-wire electrode design on a high-resistivity silicon substrate, with ions trapped at a height of 154 μm. We employed a combination of Doppler cooling, Electromagnetically Induced Transparency (EIT) cooling, and resolved-sideband cooling to prepare the ions in the motional ground state. Coherent manipulations were performed using both a 729 nm laser (for optical qubits between the $|\text{S}_{1/2},m_j=-1/2\rangle$ and $|\text{D}_{5/2},m_j=-3/2\rangle$ states) and microwave radiation (for qubits between the $|\text{S}_{1/2},m_j=-1/2\rangle$ and $|\text{S}_{1/2},m_j=+1/2\rangle$ states) Quantum state detection was achieved via state-dependent fluorescence using an EMCCD camera, enabling site-resolved readout. Key Results Low Room-temperature Heating Rates: The trap exhibited low heating rates, measured to be 0.074(8) quanta/ms in the axial direction (at 833 kHz) and 0.237(51) quanta/ms in the radial direction (at 1.3 MHz). The spectral density of electric-field noise is on the order of $10^{-13}$ ${{\rm{V}}^2 /{\rm{m}}^{2} {\rm{Hz}}}$ at trap frequencies above 500 kHz, ranking among the best for room-temperature devices. The spectral density of electric-field noise followed an approximate $f^{-2.52(22)}$ dependence, potentially influenced by external filtering circuits. High-Fidelity Single-Ion Control A single 40Ca+ ion was cooled to an average phonon number of 0.04(2) in its axial motion. High-fidelity coherent operations were demonstrated: carrier Rabi oscillations using the 729 nm laser showed a single-pulse fidelity of approximately 98.98(8)%, while microwave-driven operations achieved a fidelity of 99.95(2)%. Ramsey interferometry with microwaves revealed a coherence time $T_2^*$ of 5.0(4) ms.Site-Resolved Multi-Ion Coherent Control: The core achievement was the global coherent manipulation of ion chains containing up to 20 ions. We characterized the system by driving motional sideband transitions on various axial modes of 5- and 6-ion chains. The resulting Rabi oscillations, measured with site-resolved fluorescence, clearly showed the collective dynamics and mode-dependent coupling strengths dictated by the normalized mode eigenvectors. Furthermore, global carrier transitions were demonstrated on a 2D zigzag crystal of 20 ions, confirming the ability to execute simultaneous operations on a large qubit array. Global Control of 2D Ion Crystals With 20 ions, a 2D zigzag crystal was formed and globally addressed using both laser and microwave drives. Laser-driven carrier transitions showed strong decay due to multimode motional coupling, while microwave-driven oscillations remained nearly decay-free, consistent with the Lamb–Dicke parameter being negligible for microwave fields. Conclusion We have successfully demonstrated that our room-temperature surface-electrode trap can support low-heating confinement, high-fidelity single- and multi-qubit operations, and coherent control of large ion arrays. The site-resolved observations of mode-dependent coupling highlight the potential for exploiting collective vibrational modes for selective quantum control. These results validate the trap as a robust and promising platform for medium-scale quantum information processing and quantum simulation at room temperature. Future work will focus on structural optimizations to reduce radial heating and integration with cryogenic systems to further suppress noise, ultimately advancing toward large-scale quantum computing architectures.
Recognition of fractional orbital angular momentum modes based on convolutional neural network -transformer model combined with triangular diffraction
ZHOU Yuncheng, ZHANG Rongxiang, LIU Tao, BI Huicong, HOU Fang, WANG Xinyu
Abstract +
Utilizing fractional vortex beams (FVBs) as information carriers can significantly enhance the capacity of communication systems. However, the small gap difference between adjacent fractional orbital angular momentum (FOAM) modes makes FVBs highly sensitive to atmospheric turbulence. Therefore, precise measurement of distorted FOAM modes is crucial for practical FVBs-based communication systems. To fully utilize the beam intensity information and the triangular diffraction pattern information, we propose a dual-channel deep learning model with a hybrid architecture combining convolutional neural network (CNN) and vision transformer (ViT). The beam intensity information is extracted using the CNN, while the diffraction pattern information is extracted using the ViT. Then, by combining the complementary feature information from the intensity distribution of FVBs and their triangular diffraction patterns, this model can effectively identify the FOAM modes. The results show that the proposed model only requires a relatively small number of samples to reach convergence, namely 100 sets of data under weak turbulence and 400 sets of data under strong turbulence. Moreover, within a transmission distance of 1000 m, the proposed model can identify 101 FOAM modes with a mode spacing of 0.1 with an accuracy of 100% under weak and moderate turbulences, and maintains 98.12% accuracy under strong turbulence. Furthermore, the model can expand the detection range of turbulence intensity with only a minimal loss in accuracy, exhibiting strong generalization ability under unknown atmospheric turbulence strengths, thus providing a novel approach for accurately identifying FOAM modes.
Goal-property-guided material generation: Toward on-demand construction via inverse design of materials
LIU Zhanghe, CHEN Xinyu, ZHOU Qionghua, WANG Jinlan
Abstract +
In recent years, the application of machine learning in materials science has significantly accelerated the discovery of new materials. In particular, when combined with traditional methods such as first-principles calculations, machine learning models have proven effective in screening potential high-performance materials from existing databases. However, these methods are largely limited by the known chemical spaces, making it difficult to achieve the active design of novel material structures. To overcome this limitation, generative models have become a promising tool for inverse material design, providing new avenues for exploring unknown structures and property spaces. Although existing generative models have achieved initial progress in crystal structure generation, achieving property-guided material generation remains a significant challenge. In this review paper, we first introduce the representative generative models recently applied to materials generation, including CDVAE, MatGAN, and MatterGen, and analyzes their basic abilities and limitations in structural generation. We then focus on strategies for incorporating target properties into generative models to generate the property-guided structure. Specifically, we discuss four representative methods: Con-CDVAE based on target property vectors, SCIGEN with integrated structural constraints and guidance mechanisms, a fine-tuned version of MatterGen leveraging adapter-based property control, and a CDVAE latent space optimization strategy guided by property objectives. Finally, we summarize the key challenges faced by property-guided generative models and provide an outlook on future research directions. This review aims to offer researchers a systematic reference and inspiration for advancing property-driven generative approaches in material design and provides researchers with a systematic reference and insight into the advancement of property-driven generative methods for materials design.
Influence of alloying elements on the thermodynamic and elastic properties of palladium based alloys and database construction
ZHU Hanyu, CHONG Xiaoyu, GAO Xingyu, WU Haijun, LI Zulai, FENG Jing, SONG Haifeng
Abstract +
The lower friction coefficient and superior mechanical properties of palladium (Pd) alloys make them potentially advantageous for use in high-precision instruments and devices that require long-term stable performance. However, the high cost of raw materials and experimental expenses result in a lack of fundamental data, which hinders the design of high-performance Pd alloys. Therefore, in this study, first-principles calculations are used to determine the lattice constant and elastic modulus of Pd. A model of dilute solid solutions formed by Pd with 33 alloying elements including Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and others, is established. The mixing enthalpy, elastic constant, and elastic modulus are calculated. The results show that, all other alloying elements except for Mn, Fe, Co, Ni, Ru, Rh, Os, and Ir can form solid solutions with Pd. Alloying elements from both sides of the periodic table enhance the ductility of Pd solid solutions, with La, Ag, and Zn having the most significant effects, while Cu and Hf reduce the ductility of Pd. Differential charge density analysis indicates that the electron cloud formed after doping with Ag is spherically distributed, thereby improving ductility. After doping with Hf, the degree of delocalization around the atoms is maximized, indicating a strong ionic bond between Hf and Pd, which results in a higher hardness of Pd31Hf. The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00186.
Applications of low-temperature non-equilibrium plasmas in preparation and modification of high-efficiency water electrolysis catalysts
LI Yongjian, LI Guoling, LIU Xiao, ZHENG Jie
Abstract +
Hydrogen energy, as one of the most promising clean and renewable energy sources, has received much attention due to its green production technology. Electrolytic water splitting is regarded as a critical pathway for large-scale green hydrogen production due to its environmentally friendly reaction process, high product purity, and operational simplicity, However, electrocatalysts for water electrolysis commonly face challenges such as high costs and complex synthesis processes, thereby severely hindering the industrial application. Low-temperature plasma (LTP) technology, with its advantages of mild processing conditions, high reactivity, and unique electromagnetic field effects, has demonstrated remarkable potential in the surface modification of materials. This review systematically summarizes the applications of LTP in the preparation and modification of electrocatalytic materials for water splitting, focusing on the mechanism of plasma-induced enhancement in electrocatalytic efficiency. First, the physical characteristics and fundamental principle of typical non-equilibrium low-temperature plasma are elucidated. Subsequently, recent advances in plasma-assisted modification strategies for catalytic materials are categorized and critically discussed, including surface microstructure modulation, surface property regulation and interface optimization. Finally, based on the current limitations in mechanistic understanding and practical applications, future research directions for LTP technology in catalyst design are proposed.
Internuclear-distance dependence of photoionization time delay in CO
BAI Guangru, REN Zhongxue, ZHANG Bin, YANG Yan, LANG Yue, LIU Jinlei, ZHAO Jing, ZHAO Zengxiu
Abstract +
Photoionization time delay in atoms and molecules is a fundamental phenomenon in attosecond physics, encoding essential information about electronic structure and dynamics. Compared with atoms, molecules exhibit anisotropic potentials and additional nuclear degrees of freedom, which make the interpretation of molecular photoionization time delays more intricate but also more informative. In this work, we investigate the dependence of the photoionization time delay on the internuclear distance in the $ 5\sigma \to k\sigma$ ionization channel of carbon monoxide (CO) molecules. The molecular ground state is obtained using the Hartree-Fock method, and the photoionization process is treated within quantum scattering theory based on the iterative Schwinger variational principle of the Lippmann–Schwinger equation. Numerical calculations are performed with the ePolyScat program to obtain molecular-frame differential photoionization cross sections and time delays at various internuclear distances. Our results show that the extrema of the photoionization time delay occur near the peaks and dips of the differential cross section and shift toward lower energies as the internuclear distance R increases. At low energies, the time delay along the oxygen end increases with R, while that along the carbon end decreases, which is attributed to the asymmetric charge distribution and the resulting short-range potential difference between the two atomic sites. Around the shape-resonance energy region, both cross section and time delay display pronounced peaks associated with an $ l=3$ quasi-bound state. As R increases, the effective potential barrier broadens, the quasi-bound state energy moves to lower values, and its lifetime becomes longer, leading to enhanced resonance amplitude and increased time delay. In the high-energy region, opposite-sign peaks of time delay are found along the O and C directions, corresponding to minima in the cross section. These features are well explained by a two-center interference model, where increasing R shifts the interference minima and the associated time-delay peaks toward lower energies. This study provides deeper insights into the photoionization dynamics of CO molecules, accounting for the role of nuclear motion, and offers valuable references for studying the photoelectron dynamics of more complex molecular systems.
Transport evidence for magnetic proximity effect in EuS/InAs/GaInSb heterostructure
JIA Peizhe, ZHANG Wenfeng, DU Rui-Rui
Abstract +
Magnetic proximity effects (MPE) are crucial for topological quantum devices because they enable control of boundary states between a ferromagnetic insulator and a topological insulator. The InAs/GaInSb double quantum well system—especially when combined with a superconductor and influenced by MPE—shows promise for producing topological qubits. Nonetheless, researchers still debate the exact strength of the MPE between europium sulfide (EuS) and InAs.
To directly probe the MPE, this work focuses on a EuS/InAs/GaInSb heterostructure. The heterostructure was fabricated by depositing EuS onto the passivated surface of a Hall bar formed from an InAs/GaInSb double quantum well, utilizing an electron beam evaporation system. Structural analysis using Reflection High-Energy Electron Diffraction and magnetic measurements revealed that, although the resulting EuS thin films were polycrystalline, they nonetheless displayed desired magnetic properties, making them suitable for further study of MPE phenomena.
Low-temperature magnetoresistance measurements on the fabricated Hall bar revealed several key phenomena that collectively provide evidence for the MPE. Application of a positive gate voltage caused the electron wavefunction within the InAs layer to shift toward the EuS interface, thereby enhancing the MPE. Under a perpendicular magnetic field, the magnetoresistance exhibited an increasing slope for the odd-parity component. Additionally, a transition from positive to negative magnetoresistance near zero field was observed. When an in-plane magnetic field was applied, a gate-enhanced negative magnetoresistance emerged. Hysteretic magnetoresistance, corresponding to the reversal of EuS magnetization, was also detected during these measurements.
The resistance-temperature curve for the heterostructure displayed a pronounced upturn at low temperatures. This behavior was well described by the Kondo model, indicating the presence of exchange coupling between InAs electrons and the localized magnetic moments of EuS near the interface. Such coupling is a strong indicator of the magnetic proximity effect at work in the system.
These findings collectively demonstrate the existence of a gate-tunable MPE in the EuS/InAs/GaInSb heterostructure. The ability to control the MPE through gate voltage establishes this heterostructure as a compelling platform for the exploration of proximity-induced magnetism. Furthermore, these results underscore the potential applications of such systems in the development of spin-based electronic devices and highlight their significance for future research in topological quantum computing.
Terahertz Spectroscopy Study of the Magnetic Field- and Temperature-Induced Spin-Reorientation in a-cut YbFeO3
CHEN Ying, DONG Zhitao, ZHENG Shiyun, LIU Yongzhen, JU Xuewei, CAO Yiming, WANG Xiangfeng
Abstract +
The spin-reorientation transition (SRT) in rare-earth orthoferrites offers an important platform for exploring the coupling and manipulation of spin dynamics, which is crucial for developing high-frequency spintronic and terahertz (THz) magneto-optical devices. In this work, we systematically investigate the temperature- and magnetic-field-induced SRT behavior and the associated electron paramagnetic resonance (EPR) transitions of Yb3+ ions in a-cut YbFeO3 single crystals using time-domain terahertz spectroscopy (THz-TDS). The temperature-dependent measurements from 1.6 to 300 K reveal a distinct SRT near 7 K, marked by a sudden shift of the magnetic resonance mode frequency. This indicates a transition of the Fe3+ spin configuration from the low-temperature Γ2 phase to the high-temperature Γ4 phase, driven primarily by the temperature evolution of the anisotropic Fe3+-Yb3+ exchange interaction.
Under an external magnetic field applied along the a-axis at 20 K, the system exhibits an incomplete field-induced SRT from the Γ4 phase toward the Γ2 phase. In the intermediate Γ24 phase, both the quasi-AntiFerroMagnetic (q-AFM) and quasi-FerroMagnetic (q-FM) modes are simultaneously excited, as observed in the THz absorption spectra. Notably, even at the maximum field of 7 T, the transition remains incomplete, indicating the stabilization of the intermediate phase over a wide field range. In the low-frequency region (<0.8 THz), two absorption peaks exhibiting clear blue shifts with increasing magnetic field are identified as EPR transitions between Zeeman sublevels of the crystal-field-split Kramers doublets of Yb3+ ions.
All experimental observations, including the temperature- and magnetic-field-dependent frequency responses of the q-AFM and q-FM modes as well as the evolution of the electron paramagnetic resonance signals with magnetic field, have been quantitatively described by coupling a spin dynamics model with crystal field theory. The model successfully reproduces the continuous rotation of the macroscopic Fe3+ magnetization vector within the ac plane under an applied magnetic field, revealing the microscopic mechanism of the field-induced SRT. The analysis demonstrates that the SRT process results from the competition and synergy between the external magnetic field and the anisotropic Fe3+-Yb3+ exchange interaction, which collectively modulate the internal effective field and determine the stability of the intermediate Γ24 phase.
This study confirms the effective control of spin configurations in YbFeO3 via both temperature and magnetic field, provides a deeper understanding of the Fe3+-Yb3+ exchange interaction mechanism, and offers important experimental insights for the design of terahertz functional devices based on rare-earth orthoferrites.
Study on the Effects of Interlayer Doping with Functional Groups on the Structural Stability and Electronic Structure of Bilayer Graphene
Miao Yaping, Shuli Xiao, Fan Wu, Wei Fan
Abstract +
Among the graphene family, bilayer graphene (BLG) exhibits more diverse electronic structures and higher tunability than monolayer graphene due to its unique interlayer coupling effect, emerging as a crucial branch in functionalization research. By utilizing its interlayer as an embedding channel, BLG avoids impairing graphene's intrinsic conductivity-a common issue with surface modification. Furthermore, the interlayer coupling allows for synergistic engineering of its electronic structure, yielding performance superior to that of monolayer graphene. Therefore, the interface of BLG represents a potential functionalization site. Based on the aforementioned research status and issues, all calculations in this study are performed using density functional theory (DFT) via the Vienna Ab-initio Simulation Package (VASP). To accurately describe the van der Waals (vdW) interactions (π-π stacking) between the layers of AB-stacked BLG, the DFT-D3 method is employed for vdW correction to investigate the influence of functional groups on BLG electrical properties. This study focuses on four functional groups (-OH, -CO, -CHO, and -COOH), whose contained O and H atoms can readily form chemical bonds with the carbon atoms in BLG. Through interlayer modification, the interactions between these functional groups and the carbon atoms are analyzed to realize the regulation of interlayer coupling and electronic structure characteristics of BLG. The insertion of -OH and -CHO into the interlayer of BLG results in higher stability and lower interfacial binding energy, whereas the insertion of -CO and -COOH leads to reduced stability. The Fermi level of BLG shifts to varying degrees upon the insertion of functional groups. Specifically, the insertion of -OH or -COOH causes the Fermi level to shift toward lower energy levels, reducing the highest occupied energy level. In contrast, the insertion of -CO or -CHO shifts the Fermi level toward higher energy levels, exciting more electrons to higher energy states and resulting in electron filling at elevated energy levels. The band structure of BLG undergoes significant modifications due to the insertion of functional groups. The original parabolic band dispersion is disrupted, and the band distribution becomes more complex, with altered line trajectories and crossing characteristics. Partial density of states (PDOS) and charge density difference calculations reveal orbital hybridization and charge transfer between the functional groups and BLG. All four functional groups form covalent bonds with the carbon atoms of BLG, exhibiting characteristics of chemical adsorption. Moreover, the extent of charge transfer and the perturbation of charge density vary significantly among the different functional groups. This study aims to elucidate the regulatory mechanisms and underlying principles of functional groups, providing a theoretical basis for designing BLG-based electronic materials with specific functionalities, while also enriching the research framework of interlayer functionalization in two-dimensional layered materials.
Simulations of effect of electron beam injection on dipole magnetic field confined plasma
PAN Yuhao, WANG Zhibin, YE Zhuohui, YI Zuning, CHEN Jian, XIAO Qingmei, MAO Aohua, ZHANG Zhonglin, NIE Qiuyue
Abstract +
Research into the characteristics of dipole magnetic field-confined plasmas and their interaction with charged particle beams is critical for understanding near-Earth magnetospheric plasma. In this paper, a fully relativistic electromagnetic particle-in-cell (PIC) method, implemented with the open-source code Smilei, is used to perform three-dimensional kinetic simulations of the evolution of electron beams injected into the dipole magnetic field confined plasmas. The simulation adopts a uniform grid with 256 cells in each spatial direction, neglects collisional effects, and considers a plasma consisting only of electrons and ions. The initial plasma with a number density of 1×1012 m–3 is configured as a rectangular toroidal structure with a square cross-section. An externally prescribed dipole magnetic field is applied to the simulation domain. This field is generated by an ideal current loop centered in the grid’s x-y plane, with a loop radius of 1/8 the grid length a current magnitude of 4000 A, and a maximum magnetic field strength of 6000 G. Under these conditions, the ratio of electron plasma frequency to gyrofrequency ranges from 5.3×10–4 to 3.2, and the plasma beta varies from 2.24×10–10 to 8×10–3. The grid cell size is set to 0.05 times the electron Debye length, and the time step is 0.95 times the CFL time step. The simulation runs for a total of 20000 steps to achieve a quasi-steady state. The electron beams with a temperature of 10 eV and a drift velocity of 1×107 m/s are injected from the x-min boundary of the grid at angles of 0°, 30°, and 60° relative to the positive x-axis, to explore the influence of electron beams with varying injection angles on the dipole magnetic field confined plasma.The simulation results demonstrate the spatiotemporal evolution and behavior of the electron beam and plasma. Specifically, the plasma confined by a dipole magnetic field forms a crescent-shaped shell structure that aligns with magnetic field lines, with toroidal currents of opposite directions generated inside and outside the shell. When the electron beam is injected at incident angles of 0° and 30°, drift effects cause most of beam particles to concentrate along a specific magnetic field line on the x = y plane. Additionally, the drift current induced by electron beam injection changes the distribution of the central toroidal current in the main plasma, resulting in localized enhancement and attenuation of the toroidal current. In contrast, at an injection angle of 60°, the vast majority of beam particles are scattered by the dipole magnetic field, and fail to reach the central region to interact with the main plasma. Simulation findings further indicate that when the electron beam’s injection angle relative to the magnetic field direction exceeds 20° and its drift velocity is misaligned with the dipole field center, most of beam particles scatter and are ejected from the simulation domain, precluding interaction with the dipole-confined plasma. For future experimental devices studying the interactions between electron beam and plasma in dipole magnetic field confinement systems, choosing an appropriate beam injection direction is critical to ensure that the electrons can reach the core region of the dipole field and interact with the confined plasma. This study offers valuable insights into the dynamic behavior of plasma in dipole magnetic fields, aiding space plasma research facilities in achieving their designed scientific objectives.
Covariant chiral effective field theory of baryonic non-leptonic decays
ZHANG Wei, YANG Jifeng
Abstract +
An unresolved issue in the study of baryon non-leptonic decays is that the theoretical values describing the s- and p-wave amplitudes of such decays cannot simultaneously accord well with experimental values. Compared with previous literature, this paper adopts the covariant chiral effective theory framework and calculates the one-loop corrections to the s- and p-wave amplitudes by using the extended minimal subtraction (EMS) scheme, and also takes into account the contributions from intermediate pion states that are neglected in previous studies (the contributions from intermediate decuplet states are not considered here). Unlike infrared regularization and the extended on-shell subtraction scheme, EMS is easier to implement and also avoids over-subtraction. Apart from the typical chiral logarithmic term mslnms obtained in heavy-baryon formalism, the covariant calculation retains many non-local contributions that are not negligible. These non-local contributions vary with loop diagrams and intermediate states, making the complete covariant results significantly different from those from the simple chiral logarithmic structures in heavy-baryon formalism, which may alleviate the tension between the s- and p-wave components of the decay amplitudes. Subsequent numerical analysis confirms this conjecture. Two approaches are adopted to obtain covariant theoretical predictions: s-wave fitting and p-wave fitting. According to the fitted predictions and chi-squares of fitness, the s-wave fitting yields s-wave predictions slightly inferior to those under heavy-baryon formalism, but the resulting p-wave predictions are considerably improved compared with the heavy-baryon formalism predictions. The p-wave fitting produces p-wave predictions closer to experimental values, while the heavy-baryon predictions differ significantly from the experimental values. The resulting s-wave predictions from p-wave fitting show noticeable discrepancies with experimental data, but the heavy-baryon predictions are even worse. Therefore, working in the covariant framework, the tension between s- and p-wave amplitudes for baryon non-leptonic decays is significantly alleviated in comparison with that in heavy-baryon formalism. In addition, it is found that the contributions from intermediate pion states may be neglected in many cases, but are important and must be kept for decays with smaller experimental values.
Dzyaloshinskii-Moriya Interaction in Rare-Earth Transition Metal Ferrimagnetic Materials and Spintronic Applications
ZHANG Yu, MENG Gengchen, ZHAO Zhiyuan, LEI Na, WEI Dahai
Abstract +
Magnetic exchange interactions and the magnetic structures they induce are among the key factors determining magnetization switching. Dzyaloshinskii-Moriya interaction (DMI) is an asymmetric exchange interaction arises from spin-orbit coupling and structural inversion symmetry breaking, which is one of the key mechanisms to induce non-collinear magnetic order and chiral magnetic structures, including magnetic Skyrmion, vortex, chiral domain wall, etc. These magnetic structures enable novel information proceeding devices with ultralow power consumption. More importantly, compared to conventional collinear magnetic structures, non-collinear magnetic order exhibits richer and more novel physical behaviors. With ongoing exploration and research in magnetic materials, Rare-Earth Transition Metal ferrimagnetic materials (CoGd, CoTb, GdFeCo, etc.), which combine spin-orbit coupling of rare-earth elements with the magnetic exchange of transition metals, have been discovered to exhibit ultrafast magnetization dynamics, tunable magnetic structures and rich spin transport phenomena. These properties provide an ideal material platform for studying and manipulating DMI, demonstrating significant potential in designing future high-density magnetic storage and spintronic devices. This review systematically elucidates the microscopic physical origin of DMI, outlines the fundamental characteristics of Rare-Earth Transition Metal ferrimagnetic materials and explores the coupling mechanisms between DMI and ferrimagnetic order. we introduce the fundamental properties of RE-TM systems and their applications in spin logic devices and magnetic memory devices. We focus on discussing the physical phenomena related to DMI in RE-TM systems, including the scaling relationship of DMI in RE-TM, DMI-related spin-orbit torque effects, and the principles and applications of skyrmion-based devices, which would provide both theoretical foundations and technical guidance for future development of advanced spintronic technologies.
Momentum transfer of 6Li atoms without subrecoil temperature based on Bloch oscillations
YU Shichuan, ZHANG Liang, FAN Jian, YIN Mengjia, DENG Shujin, WU Haibin
Abstract +
Atom interferometer enables high-precision measurement of recoil frequency, which is crucial for determining the fine structure constant. Large momentum transfer (LMT) based on Bloch oscillations in atom interferometers can significantly enhance the measurement precision of the recoil frequency. Typically, applying Bloch oscillations to an atomic ensemble requires the atoms to be cooled within the first Brillouin zone. However, deep cooling of lithium atoms is challenging, making it diffcult to directly apply Bloch oscillations. Therefore, this paper develops an LMT technique based on Bloch oscillations in a relatively high-temperature ensemble of 6Li atoms. By constructing a deep potential optical lattice, the high-temperature atoms can be effciently loaded into the lattice. Subsequently, the optical lattice is adiabatically chirped to suppress interband transitions of the atoms and enable atoms to accelerate with the lattice. Although the effciency of a single Bloch oscillation decreases under the tight-binding approximation, this method simultaneously relaxes the temperature requirements of the LMT technique. Consequently, we achieve a large momentum transfer of 40 recoil momenta at 80 μK (far above the recoil temperature), with the number of transferred atoms reaching up to 5 × 106. Subsequent analysis of the atomic momentum spectrum before and after the Bloch oscillations revealed that, due to Doppler broadening, the atomic momentum shows a continuous distribution between the initial momentum and the target momentum, which limits the momentum transfer effciency. It was found that for a fixed optical lattice depth and pulse duration, the momentum distribution of atoms participating in the Bloch oscillations is independent of the number of oscillations. Furthermore, atoms with initial velocities aligned with the acceleration direction of the optical lattice are more easily accelerated. This LMT technique is expected to substantially enhance the measurement precision of the 6Li atomic recoil frequency, providing an important reference for the subsequent high-precision calibration of the fine structure constant using 6Li atom interferometers.
High-Pressure Polarized Raman Device and Its Applications
WANG Zeyu, LIU Jingyi, WANG Yangbin, WANG Menghan, LI Jingye, YAN Chengxi, LEI Li
Abstract +
High-pressure polarized Raman spectroscopy (HPRS) refers to a spectroscopic technique in which a diamond anvil cell (DAC) is employed as the pressure-generating device, and the polarization orientations of both incident and scattered light are systematically controlled to measure the angular dependence of Raman spectral intensities under varying pressures. This enables the quantitative extraction of the pressure evolution of Raman tensor elements. In this study, we developed an in-situ high-pressure polarized Raman setup based on a backscattering configuration incorporating a half-wave plate, allowing continuous variation of the polarization angle without rotating the sample. Quantitative determination of Raman tensor elements was achieved through polar coordinate fitting of the measured intensity profiles. Singlecrystal Si(100), commonly used for Raman calibration, and two-dimensional Te(110) flakes exhibiting in-plane anisotropy were selected as model systems for investigation. Our results show that over the pressure range of 0~12 GPa, the angular distribution pattern and periodicity of Si(100) remain unchanged, while the main Raman peak exhibits an approximately linear blue shift with increasing pressure. The Raman tensorelement associated with the active mode decreases according to an inverse power-law function, reflecting the response of the polarizability derivative to volume compression in the absence of phase transitions. For two-dimensional Te(110), the in-plane anisotropy increases with pressure, accompanied by deviations of certain modes from ideal symmetry-predicted behavior. Notably, the ratio of Raman tensor elements displays an inflection point near 1.5 GPa, transitioning from a decreasing to an increasing trend, with clearly observable changes in polarized Raman responses within the 1.2~1.6 GPa range. It is in close proximity to the electronic structure phase transition point determined from transport experiments (~2 GPa). Collectively, studies on single-crystal Si(100) and two-dimensional Te(110) demonstrate that HPRS is a robust in-situ method for probing symmetry evolution, anisotropic behavior, and incipient electronic rearrangements in materials under compression.
Tunable Spectrum Dual-Parameter Multiplexed Quantum Weak Measurement
Wang Ao, Zhang Min, Gao Shuqi, Liu Qingchen, He Li, Guo Xiaomin, Guo Yanqiang, Xiao Liantuan
Abstract +
Quantum weak measurement technology has significantly advanced the detection limits of quantum precision measurement due to its minimal disturbance to the measured system and the weak value amplification (WVA) effect. This technique has been successfully applied in phase difference and time difference measurements, leading to a series of important achievements. Previous standard weak measurement typically utilize only a single momentum parameter as the measurement pointer and rely on a single weak interaction (SWI) to detect minute phase shifts. Although some studies have attempted to introduce quantum resources to further enhance the amplification factor and measurement precision, the practical application is hindered by thechallenges associated with quantum state preparation. Therefore, practical quantum weak measurement systems still require in-depth research and exploration to overcome these technical bottlenecks.
In this study, we propose and experimentally validate a dual -parameter quantum weak measurement scheme based on tunable spectral control and iterative weak interactions. Theoretical analysis demonstrates that adjusting the spectral width and the number of weak interactions, can effectively enhance the weak value amplification effect. Experimentally, a phase weak measurement system based on iterative weak interactions (IWI) was constructed using a tunable light source as the optical input. The setup incorporates three sets of half-wave plates (HWP) to realize triple weak interactions. By fixing the postselection angle and rotating the HWP to introduce a weak phase delay, high-precision detection of the phase shift is achieved by monitoring both the spectral shift and light intensity variations. Experimental results indicate that at a spectral width of 700 GHz, the momentum parameter M achieves the 4.06 × 10-8 rad optimal phase difference measurement accuracy, which is 2.78 times higher than that of single weak interactions (SWI). As the spectral width decreases, the signal-to-noise ratio gradually degrades, and the shift signal of parameter M is submerged in the electronic noise of the spectrometer, necessitating a switch to the intensity parameter I for detection. When a narrow-linewidth source with a linewidth of 500 kHz isemployed, the intensity parameter I enables phase difference measurements at the level of 5.99×10-7 rad while maintaining a high signal-to-noise ratio (SNR) of 17.4 dB. Its measurement precision is 2.97 times higher than that of SWI. In optical experiments, the optical phase can serve as a proxy for other physical quantities such as displacement, temperature, and magnetic field strength. Therefore, this scheme provides crucial technical support for practical enhanced quantum precision sensing.
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