Science China Physics, Mechanics & Astronomy最新文献

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.

Magnetic skyrmions, topologically protected spin textures, are promising for both fundamental studies of topological magnetism and spintronic applications in data storage, logic processing, true random number generators, and neuromorphic computing. Yet, their energy dissipation, a key metric for evaluating manipulation efficiency and dynamics, remains elusive. Here, magnetotropic dissipation in B20 MnSi is characterized by dynamic cantilever magnetometry (DCM). Magnetotropic dissipation in the skyrmion phase is about one order of magnitude smaller than in topologically trivial helical and conical states, which is attributed to the topological characteristic that preserves spin configurations and minimizes energy loss to the electron/ phonon heat bath, as confirmed by micromagnetic simulations. A magnetotropic dissipation phase diagram is further constructed, revealing little temperature dependence of skyrmion magnetotropic dissipation, indicative of negligible magnonic contributions to the magnetotropic dissipation process. Our results reveal the low magnetotropic dissipation characteristic and underlying mechanisms of skyrmions, and demonstrate that DCM can resolve dissipation down to 7×10⁻¹⁴ kg/s, enabling detailed investigations of magnetic materials at microscale dimensions.

Quasi-one-dimensional RbMn₆Bi₅, the first pressure-induced ternary Mn-based superconductor, exhibits a phase diagram analogous to those of cuprate and iron-based superconductors, with superconductivity neighboring antiferromagnetic order. Here, we use ⁵⁵Mn and ⁸⁷Rb nuclear magnetic resonance (NMR) to unravel its magnetic structure and fluctuations. Above the Néel temperature (T_N), strong antiferromagnetic fluctuations dominate, characteristic of a paramagnetic state with pronounced spin-lattice relaxation rate enhancement. Below T_N, a first-order phase transition establishes a commensurate antiferromagnetic order, where Mn atoms at the pentagon corners exhibit distinct magnetic moments with different orientations, while the central Mn atom carries no magnetic moment. The complex magnetic architecture, revealed by zero-field and high-magnetic-field NMR spectra, contrasts with earlier neutron diffraction models proposing uniform spin density waves, instead supporting localized moment ordering with charge rearrangement. The proximity of robust antiferromagnetic fluctuations to the high-pressure superconducting phase suggests a potential role for magnetic excitations in mediating unconventional Cooper pairing, akin to paradigmatic high-T_c systems. These findings provide critical insights into the interplay between geometric frustration, magnetic order, and superconductivity in manganese-based materials.

Confined gas and ionic hydrates play vital roles in energy storage, carbon capture, and water desalination. Yet, the fundamental interactions between water films and hydrophobic molecules remain poorly understood. Here, we investigated nanoconfined monolayer methane hydrates encapsulated within graphene capillaries, exploring their phase behavior through crystal structure prediction combined with a machine-learning force field. We identified a thermodynamically stable two-dimensional tetragonal compound CH₄(H₂O)₄ under moderate pressures. Its hydrogen bonding network markedly differs from that of 2D pure or porous ice, giving rise to multiple plastic phases in which methane and water molecules rotate. Remarkably, 2D CH₄(H₂O)₄ transitions into a superionic state featuring proton diffusion at pressures as low as ∼3 GPa, substantially lower than that required for 2D ice. The calculated phase diagram further reveals that CH₄ molecule incorporation elevates the melting temperatures above 350 K while reducing the onset pressure for superionicity. These findings provide fundamental insight into hydrophobic gas hydrate under nanoscale confinement and open new avenues for applications in energy storage and hydrocarbon capture.

We introduce a mock galaxy catalog built for the China Space Survey Telescope (CSST) extragalactic surveys using the primary runs of the Jiutian N-body simulation suites. The catalogs are built by coupling the galaxy evolution and assembly (gaea) semi-analytical model of galaxy formation with merger trees extracted from the simulations using the hierarchical bound-tracing (hbt+) algorithm. The spectral energy distributions (SEDs) and broadband magnitudes are computed using the neural-network-based stellar population synthesizer StarDuster, which is trained on radiative transfer simulations to account for detailed galaxy geometry in modeling dust obscuration. Galaxy light-cones up to z = 5 are subsequently generated with the Blic light-cone builder, which interpolates the properties of galaxies over time using an optimized interpolation scheme. The resulting catalogs exhibit good convergence in many statistical properties of the galaxy population produced from two different resolution simulations. The catalogs reproduce a number of observed galaxy properties across a range of galaxy mass and redshift, including the stellar mass functions, the luminosity function, gas mass fraction, galaxy size-mass relation, and galaxy clustering. We also present the photometric and redshift distributions of galaxies expected to be observed in the CSST surveys.

Recent studies of moiré physics have unveiled a wealth of opportunities for significantly advancing the field of quantum phase transitions. However, properties of reentrant phase transitions driven by moiré strength are poorly understood. Here, we investigate the reentrant sequence of phase transitions and the invariant of the universality class in moiré-modulated extended Su-Schrieffer-Heeger (SSH) model. For the simplified case with intercell hopping w = 0, we analytically derive renormalisation relations of Hamiltonian parameters to explain the reentrant phenomenon. For the general case, numerical phase boundaries are calculated in the thermodynamic limit. The bulk boundary correspondence between zero-energy edge modes and the entanglement spectrum is revealed from the degeneracy of both quantities. We also address the correspondence between the central charge obtained from entanglement entropy and the change in winding number during the phase transition. Our results shed light on the understanding of universal characteristics and bulk-boundary correspondence for moiré induced reentrant phase transitions in 1D condensed-matter systems.