Highlights
SPECIAL TOPIC—Order tuning in disordered alloys
COVER ARTICLE
2025, 74 (8): 086101.
doi: 10.7498/aps.74.20250097
Abstract +
SPECIAL TOPIC—Order tuning in disordered alloys
EDITOR'S SUGGESTION
2025, 74 (8): 086102.
doi: 10.7498/aps.74.20250128
Abstract +
Multi-principal element alloys (MPEAs), also known as high-entropy alloys (HEAs), are novel materials that have received significant attention due to their exceptional mechanical properties, thermal stability, and resistance to wear and corrosion. These alloys are typically composed of multiple principal elements in near-equal atomic proportions, forming solid solution phases such as face-centered cubic (FCC) or body-centered cubic (BCC) structures. Despite the promising applications, a more in-depth understanding of the atomic-level behavior, particularly, lattice distortion and atomic strain, is essential to better design and optimize these materials in extreme environments. This study focuses on systematically investigating the atomic-scale lattice distortion characteristics and their influence on atomic strain in three representative BCC-based MPEAs: TaWNbMo, TiZrNb, and CoFeNiTi. We utilize molecular dynamics (MD) simulations to explore the local atomic strain distributions in these alloys at various temperatures. Von Mises strain and volumetric strain are employed as key descriptors to quantify the atomic strain, providing a clear representation of how lattice distortion on an atomic scale influences the overall strain behavior. The study specifically addresses the effects of atomic radius differences, chemical short-range ordering, and temperature on the strain characteristics of the alloys. The results obtained indicate that an increase in lattice distortion corresponds to a broader distribution of von Mises strain and volumetric strain, with strain values significantly amplified. More precisely, alloys with larger atomic radius differences exhibit greater volumetric strain, reflecting the influence of atomic size disparity on strain distribution. Furthermore, the formation of chemical short-range order (CSRO) significantly mitigates lattice distortion and atomic strain. This finding highlights the importance of short-range atomic ordering in enhancing the stability of the alloy structures, thus potentially improving their mechanical properties. Temperature effects are also investigated, revealing that elevated temperature induces more intense atomic vibration, which in turn increases the atomic strain. The findings underscore the complex interplay between atomic-scale phenomena and macroscopic mechanical properties, offering new insights into the microscopic mechanical behavior of high-entropy alloys. This study contributes to a better understanding of the underlying mechanisms driving atomic strain and lattice distortion in MPEAs. The results provide valuable theoretical insights that can guide the design of high-performance alloys tailored for high-temperature and extreme environments. By addressing the key factors influencing atomic strain, such as atomic radius, chemical ordering, and temperature, this work lays the foundation for future research aimed at enhancing the mechanical performance of MPEAs in various industrial applications.
EDITOR'S SUGGESTION
2025, 74 (8): 080701.
doi: 10.7498/aps.74.20250028
Abstract +
Diamond is a kind of extremely functional material, which is widely used in the fields of industry, science and technology, military defense, medical and health, jewelry, and others. However, its application in the semiconductor field is still limited, because its electrical transport performance has not yet met the requirements of semiconductor devices. In order to improve the electrical transport performance of diamond as much as possible, the synthesis of diamond single crystal is studied by adding B2S3 to the synthesis system using temperature gradient growth (TGG) method at a pressure of 6.5 GPa in this work. The growth rate of the synthesized diamond crystal decreases from 2.19 mg/h to 1.26 mg/h, indicating that the growth rate of diamond is dependent not only on the growth driving force, but also on the impurity element in the synthetic cavity. Additionally, with the increase of additive dosage, the color of the synthesized diamond crystal changes from yellow to baby blue . Raman measurement results indicate that the obtained diamond appears as a single sp3 hybrid phase without the sp3 hybrid graphite phase. However, the corresponding Raman characteristic peak of the as-grown diamond crystal is located at about 1331 cm–1 and tends to move towards low wave number. According to Fourier Transform Infrared Spectrometer (FTIR) measurement results, the absorption peaks at 1130 cm–1 and 1344 cm–1 are attributed to nitrogen defects. It is found that the nitrogen defect concentration of the synthesized diamond crystal decreases gradually from about 300×10–6 to 60×10–6. Furthermore, the electrical transport performance of the synthesized diamond is characterized by Hall effect measurement. Diamond has insulating properties due to the absence of any additives in the synthetic cavity. However, the results indicate that when B2S3 is introduced into the synthetic system as additive, there is almost no difference in carrier Hall mobility, but the difference in carrier concentration is as high as two orders of magnitude. Furthermore, the resistivity of the synthesized [111]-oriented diamond crystal decreases to 45.4 Ω·cm, due to the addition of B2S3 to the synthesis system. However, it is worth noting that the resistivity of the diamond crystal synthesized with 0.002 g B2S3 and Ti/Cu additives in the synthesis system drops sharply to 0.43 Ω·cm. Therefore, the nitrogen defects in diamond will have an important effect on its conductivity. It provides an important experimental basis for applying diamond to semiconductor field.
EDITOR'S SUGGESTION
2025, 74 (8): 084205.
doi: 10.7498/aps.74.20250021
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The mechanism of controlling single-photon scattering in a hybrid system consisting of superconducting qubits coupled to a Su-Schrieffer-Heeger (SSH) topological photonic lattice is investigated under the influence of an artificial gauge field. This research is driven by the growing interest in the intersection between quantum optics and condensed matter physics, particularly in the field of topological quantum optics, where the robustness of photon transport against defects and impurities can be used for quantum information processing. To achieve this, a theoretical model, which incorporates the phase of the artificial gauge field into the coupling between superconducting qubits and the SSH photonic lattice, is developed in this work. The analytical expressions for the reflection and transmission amplitudes of single photons are derived by using the probability-amplitude method. The results show that the artificial gauge field can effectively control single photon scattering in both the upper energy band and the lower energy band of the SSH lattice, thereby enabling total transmission in the upper band and total reflection in the lower band. This band-dependent scattering behavior exhibits a high degree of symmetry with respect to the lattice momentum and energy bands. Importantly, the reflection coefficient can be made independent of the lattice coupling strength and dependent solely on the topological properties of the lattice. This finding suggests a robust method of detecting topological invariants in photonic lattices. Furthermore, our analysis is extended to various coupling configurations between superconducting qubits and the photonic lattice, highlighting the versatility of the artificial gauge field in manipulating photon transport. These findings not only provide new insights into the control of photon transport in topological photonic lattices, but also open the door to the development of novel quantum optical devices and robust quantum information processing platforms.
EDITOR'S SUGGESTION
2025, 74 (8): 087801.
doi: 10.7498/aps.74.20250005
Abstract +
Rare-earth orthoferrites (RFeO3) have received significant attention due to their intricate magnetic interactions and potential applications in ultrafast spintronic devices. Among them, DyFeO3 exhibits rich magnetic phase transitions driven by the interplay between Fe3+ and Dy3+ sublattices. Previous studies mainly focused on temperature-induced spin reorientation near the Morin temperature (TM~50 K), but there has been limited exploration of magnetic phase behavior under external fields above TM. This work aims to systematically investigate the temperature- and magnetic-field-dependent magneto-dynamic properties of a-cut DyFeO3 single crystals, with an emphasis on identifying novel phase transitions and elucidating the underlying mechanisms involving Fe3+-Dy3+ anisotropic exchange interactions. High-quality a-cut DyFeO3 single crystals are grown using the optical floating zone method and characterized by X-ray diffraction (XRD) and Laue diffraction. Time-domain terahertz spectroscopy (THz-TDS) coupled with a superconducting magnet (0–7 T, 1.6–300 K) is employed to probe the ferromagnetic resonance (FM) and antiferromagnetic resonance (AFMR) modes. By analyzing the frequency trends in the spectra, the response of internal magnetic moments to external stimuli can be inferred. In the zero magnetic field experiment, it is found that the temperature induced spin reorientation (Γ4→Γ1) occurs at Morin temperature (~50 K) with temperature decreasing. A broadband electromagnetic absorption (0.45–0.9 THz) occurs below 4 K, which is attributed to electromagnons activated by broken inversion symmetry in the Dy3+ antiferromagnetic state. Above the Morin temperature, the absorption spectra of the sample are measured at constant temperatures (70, 77, 90, 100 K) and magnetic fields ranging from 0 to 7 T. The experimental results show that with the increase of magnetic field, a new magnetic phase transition occurs (Γ 4 → Γ 24 → Γ 2 → Γ 24 → Γ 2 ), and the critical magnetic field of the phase transition varies with temperature. The phase transitions arise from the competition between external magnetic fields and internal effective fields generated by anisotropic Fe3+-Dy3+ exchange. These findings contribute to the further understanding of the magnetoelectric effects in RFeO3 systems and provide a roadmap for using field-tunable phase transitions to design spin-based devices .
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SPECIAL TOPIC—Precision spectroscopy of few-electron atoms and molecules
EDITOR'S SUGGESTION
2025, 74 (8): 083101.
doi: 10.7498/aps.74.20241728
Abstract +
SPECIAL TOPIC—Correlated electron materials and scattering spectroscopy
EDITOR'S SUGGESTION
2025, 74 (8): 087402.
doi: 10.7498/aps.74.20241402
Abstract +
Unconventional superconductivity often competes or coexists with a variety of complex material states. In cuprate superconductors, there exist states including spin order, charge order, the pseudogap state, and the strange metal phase. A comprehensive understanding of their relationship is fundamental to establishing the mechanism of high-temperature superconductivity. Spin dynamics in cuprates has been extensively investigated using inelastic neutron scattering, but charge correlations remain far less understood. The latest development of resonant X-ray scattering (RXS) has been able to detect charge correlations with unprecedented sensitivity. A series of RXS studies have revealed that there universally exist the charge correlations in cuprate materials, which covers a wide range of the phase diagram. Resonant inelastic X-ray scattering (RIXS) experiments further show the dynamical behaviors of charge order. These findings highlight the important influence of charge correlations on the properties of cuprates. In this paper, we review the latest research progress in the charge order in cuprates by using RXS, with a particular emphasis on RIXS experiments. Our focus is placed on recent works on dynamical charge correlations at high temperatures as well as uniaxial strain tuning of charge order. We discuss topics including the underlying interactions, microscopic structure and symmetries, and the possible influence of charge order on both the superconducting and normal states.
EDITOR'S SUGGESTION
2025, 74 (8): 088703.
doi: 10.7498/aps.74.20241654
Abstract +
SPECIAL TOPIC—Order tuning in disordered alloys
EDITOR'S SUGGESTION
2025, 74 (8): 086103.
doi: 10.7498/aps.74.20250141
Abstract +
Medium-entropy alloys (MEAs), renowned for their outstanding strength and ductility, possess great potential for high strain-rate applications. This study focuses on a NiCoV-based MEA system, and proposes a novel alloy design strategy to fabricate the (NiCoV)95W5 alloy by introducing 5% (atomic percent) high-melting-point tungsten through vacuum arc melting coupled with thermomechanical processing. Split Hopkinson pressure bar (SHPB) experiments are conducted to elucidate the dynamic response mechanism and deformation behavior under high strain rates (2000－6000 s–1). The results show that due to severe lattice distortion, the enhanced phonon drag effect at elevated strain rates results in a substantial increase in yield strength from 720 MPa (10–3 s–1) to 1887 MPa (6000 s–1), an increase of 162%, accompanied by a relatively high strain-rate sensitivity (m = 0.42). Microscopic analysis reveals the multi-scale cooperative deformation mechanism of the alloy system under high strain rate. When the strain rate is 2000 s–1, the alloy exhibits a low dislocation density dominated by dislocation planar slip. As the strain rate increases to 4000 s–1, the increased flow stress and deformation promote the proliferation and entanglement of a large number of dislocations into high-density dislocation cells. The accumulation of dislocation stress leads to the coordinated deformation of precipitates and releases stress concentration at the phase interface. When the strain rate further increases to 6000–1, severe plastic deformation will lead to the formation of nanotwins within the matrix, which is the main strain hardening. This study elucidates the dynamic response mechanism of NiCoV MEA mediated by tungsten doping, providing a guidance for designing novel structural materials with excellent dynamic mechanical responses.
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