Science China Physics, Mechanics & Astronomy最新文献

Majorana zero modes (MZMs), promising for topological quantum computation, are naturally hosted in vortices of two-dimensional topological superconductors (TSCs). However, precise control and braiding of these vortex-bound MZMs remain a significant challenge. This work proposes and numerically demonstrates a novel braiding scheme utilizing a programmable matrix of spintransfer torque (STT) devices (STT-matrix) integrated with a TSC layer. By selectively activating individual STT elements, their localized stray fields enable deterministic manipulation, including driving, braiding, and fusion, of superconducting vortices and their associated MZMs. We establish a comprehensive simulation framework combining finite element analysis for STT-induced vortex formation, time-dependent Ginzburg-Landau equations for vortex dynamics and time-dependent Bogoliubov-de Gennes equations for MZM evolution. Simulations confirm the STT-matrix’s capability for high-fidelity vortex manipulation and demonstrate MZM braiding dynamics. We quantify the impact of vortex acceleration and finite MZM coupling on braiding fidelity, showing that it can be optimized by adjusting STT spacing and vortex separation. Furthermore, we demonstrate controlled MZM fusion and measure the resultant energy splitting. This STT-matrix-based approach offers a highly versatile, scalable, and potentially practical platform for operating MZMs within TSC vortices, advancing the development of fault-tolerant topological quantum computation.

Chiral and nonreciprocal quantum devices are crucial for signal routing and processing in a quantum network. In this work, we study the chirality and nonreciprocity of a giant atom coupled to a one-dimensional waveguide. We clarify that the chiral emission of the giant atom is not directly related to the time-reversal symmetry breaking but to the mirror-symmetry breaking. We propose a passive scheme, by extending the legs of the giant atom, to realize the chiral emission without breaking time-reversal symmetry. We prove that the time-reversal symmetry breaking alone via nonuniform coupling phases is not sufficient for the nonreciprocal single-photon scattering of the giant atom. The nonreciprocity needs both the time-reversal symmetry breaking and the finite external dissipation of the giant atom. Our work clarifies the roles of symmetries in the chirality and nonreciprocity of giant-atom systems and paves the way for the design of on-chip functional devices with superconducting giant atoms.

Recently, the films of the Ruddlesden-Popper (RP) nickelate superconductors, in which the (La,Pr)₃Ni₂O₇ system exhibits a remarkable transition temperature T_c exceeding 40 K, were synthesized at ambient pressure. We systematically investigate the band structures and electronic correlation effects to identify the key factors controlling superconductivity and pathways to enhance T_c. Based on density functional theory (DFT) calculations, we construct a bilayer two-orbital ((3d_{{3{z}^{2}}-{r}^{2}}) and (3d_{{{x}^{2}}-{y}^{2}})) tight-binding model for a series of in-plane compression mimicking the substrate effect. We find the band energy at the M point drops with the compression, leading to an increase in the density of states at the Fermi level, in stark contrast to the behavior of the bulk under pressure. We then apply the functional renormalization group (FRG) method to study the electronic correlation effect on the superconductivity. We find the s_±-wave pairing symmetry remains robust in the films, the same as the bulk. But somewhat surprisingly, for the films, we find T_c can be enhanced by reducing the in-plane lattice constant, increasing the out-of-plane lattice constant, or further electron-doping. These findings are consistent with the itinerant picture of the superconductivity induced by spin-fluctuations and provide theoretical support for further boosting T_c in future experiments.

The growing usage of industrial dyes makes the sewage treatment a global issue, therefore low-cost, highly efficient catalysts are urgently demanded for wastewater purification. We present an ultrasonic-engineered catalytic technology, which can achieve an extremely high efficiency in azo dye degradation via a tiny dosage of 0.1 g L⁻¹ (only one-fifth of the normally used dosage) Fe₈₁Si₉B₁₀ amorphous powders (APs) with a low activation energy of 45.32 kJ mol⁻¹ and a high reaction rate of 0.70291 min⁻¹. The non-destructive ultrasonic vibration (UV) treatment with very short processing times (0.43–1.08 s) amplifies degradation efficiency by an astonishing 55-fold compared to untreated APs. Combined with high-energy X-ray diffraction and small-angle neutron scattering analyses, we reveal that the UV-induced structural reconstruction at both short- and medium-range order effectively lower reaction energy barriers while accelerating charge transfer kinetics. The high-energy ultrasonic attacks promote the exposure of massive fresh active sites, which enhance the Fe²⁺/Fe³⁺ redox circulation and thereby lead to the fast Fenton-like oxidation processes. By integrating ultrasonic physics with amorphous materials, this work develops an energy-efficient catalytic activation method, enabling sustainable water purification and innovative pollutant treatment strategies.

Accurate targeting is critical for the effectiveness of transcranial focused ultrasound (tFUS) neuromodulation. While CT provides accurate skull acoustic properties, its ionizing radiation and poor soft tissue contrast limit clinical applicability. In contrast, MRI offers superior neuroanatomical visualization without radiation exposure but lacks skull property mapping. This study proposes a novel, fully CT-free simulation framework that integrates MRI-derived synthetic CT (sCT) with efficient modeling techniques for rapid and precise tFUS targeting. We trained a deep-learning model to generate sCT from T1-weighted MRI and integrated it with both full-wave (k-Wave) and accelerated simulation methods—hybrid angular spectrum (kW-ASM) and Rayleigh-Sommerfeld ASM (RS-ASM). Across five skull models, both full-wave and hybrid pipelines using sCT demonstrated sub-millimeter targeting deviation, focal shape consistency (FWHM ∼3.3–3.8 mm), and <0.2 normalized pressure error compared to CT-based gold standard. Notably, the kW-ASM and RS-ASM pipelines reduced simulation time from (∼3320 ±1270) to (187±27) and (345±85) s respectively, achieving ∼94% and ∼90% time savings. These results confirm that MRI-derived sCT combined with innovative rapid simulation techniques enables fast, accurate, and radiation-free tFUS planning, supporting its feasibility for scalable clinical applications.

The performance sensitivity of quasi-zero-stiffness (QZS) isolators to load-position mismatches poses significant challenges and hinders their practical implementation. Herein, a translation-scaling coordinated transformation method is proposed for decoupled adjustment of the rated load and equilibrium position. By coordinating translation and scaling transformations of negative and positive stiffnesses, the rated load and equilibrium position can be independently tuned, thereby mitigating performance sensitivity under time-varying operating conditions. Based on this method, a load-position decoupled QZS isolator (LPD-QZS) is developed and systematically investigated. A liftable nested magnet-coil pair is employed to generate translatable and scalable negative stiffness, while an end-to-end magnet-coil pair combined with a membrane spring pair provides nonuniformly scalable positive stiffness. Analyses reveal and verify the tunable stiffness characteristics and the effectiveness of the translation-scaling coordinated transformation in achieving load-position decoupled adjustment, as well as the distinctive behavior arising from it. Finally, offline and online tests are conducted to evaluate the robustness of the LPD-QZS under varying rated loads and equilibrium positions. Sweep excitation tests indicate that the LPD-QZS exhibits excellent low-frequency vibration isolation performance, with a low isolation frequency starting from 3.3 Hz, in drastic contrast with the degraded performance without load-position decoupled adjustment under load-position mismatches. Significantly, through translation-scaling coordinated transformation, the LPD-QZS preserves its QZS characteristic across various applied loads and operating positions, highlighting its potential for practical engineering applications, particularly in multi-leg QZS platforms.

The discovery of superconductivity in pressurized Ruddlesden-Popper (RP) nickelates has provided new perspectives on the mechanism of high-temperature superconductivity. Up to now, most experiments concentrated on the lanthanum-related RP phase, so the discovery of new superconducting RP nickelates is highly desirable to reveal their generality. Here we report the observation of superconductivity in Pr₄Ni₃O₁₀ single crystals above 10 GPa, achieving a maximum T_c of 39 K without saturation, significantly exceeding the value of 25–30 K of La₄Ni₃O₁₀. Ultrasensitive magnetic susceptibility measurements under high pressure indicate bulk superconductivity with appreciable superconducting volume fractions. Unlike La₄Ni₃O₁₀, the electronic structure of the high-pressure phase of Pr₄Ni₃O₁₀ exhibits a dramatic metallization of the σ-bonding band consisting of three (d_{z^{2}}) orbitals and van Hove singularity of coupled bands of (d_{x^{2}-y^{2}}) orbitals near the Fermi level, similar to La₃Ni₂O₇. These findings reveal some generic features of both crystal and electronic structures for high-temperature superconductivity in nickelates and multi-layer cuprates.

The recently discovered trilayer nickelate superconductor La₄Ni₃O₁₀ under pressure has emerged as a promising platform for exploring unconventional superconductivity. However, the pairing mechanism remains a subject of active investigations. With large-scale density matrix renormalization group calculations on a realistic two-orbital trilayer Hubbard model, we elucidate the superconducting (SC) mechanism in this system. Our results reveal distinct magnetic correlations in the two different orbitals: while the (d_{{z}^{2}}) orbital exhibits both interlayer and cross-layer antiferromagnetic (AFM) correlations, the (d_{{x}^{2} - {y}^{2}}) orbital shows exclusively cross-layer AFM correlations, rendering a quasi-long-range SC order in the latter. We demonstrate that the Hund’s rule coupling is essential for forming the SC order, and discuss the effects of kinetic AFM correlation and Hubbard repulsive U. Our findings motivate a further simplification of the trilayer Hubbard to an effective bilayer mixed-dimensional Hubbard model, providing a unified framework for understanding interlayer SC in both trilayer and bilayer nickelates.

The discovery of Ni-based superconductors has brought new hope to the field of high-temperature superconductivity. Understanding the dimensional characteristics and anisotropy of nickelate superconductors has become a central focus in current research. However, the nature of the nickelate superconductivity, especially the transition between 2D and 3D superconductivity, remains debated. In this study, we investigated the magnetic field-dependent electrical transport behaviors of infinite-layer nickelates. The La_0.8Sr_0.2NiO₂ films exhibit highly anisotropic superconductivity, which fits well with the 2D Tinkham model, indicating a purely 2D superconducting nature. In contrast, the Nd_0.8Sr_0.2NiO₂ films show isotropic behavior with a mixed 2D + 3D superconducting characteristics. This “mixed 2D + 3D superconducting behavior” is typically associated with the complexity of the electronic band structure in the material. Through a systematic comparison of two model systems with distinct rare-earth orbital contributions, we propose a new perspective based on orbital selectivity. The observed difference likely originates from Nd_0.8Sr_0.2NiO₂ incorporates the Nd (5d_{{z}^{2}}) orbital, adding a 3D component. Its interaction with the Ni (3d_{{x}^{2} - {y}^{2}}) orbital leads to orbital-selective pairing. Theoretical calculations provide key evidence that the Nd-based system exhibits greater isotropy and 3D character compared to the La-based system. Our study thus suggests that orbital selectivity serves as a critical mechanism governing the superconducting properties, and the distinction between rare-earth elements (such as La and Nd) ultimately influences the dimensional characteristics of superconductivity through this mechanism.