arXiv subjects

Yuze Xu

Publications and source records attributed to Yuze Xu.

3 recordsLinked to original sources

arXiv2026

Hardness of A/E-Design under Partition Constraints

We consider the A/E-design problem under partition constraints: Given vectors $v_1,\ldots,v_N\in \R^d$ and a partition matroid on $[N]$, find a base $S$ of the matroid that minimizes $\tr(M(S)^{-1})$ or $\lambda_{\max}(M(S)^{-1})$ where $M(S)=\sum_{i \in S} v_i v_i^\top$. In contrast to D-design, where good estimation and approximation guarantees are known as a function of $d$, we show that no reasonable approximation exists for A/E-design. This answers a question of Brown, Laddha and Singh. The proof is based on an elementary reduction from three-dimensional matching.

cs.DS↗

arXiv2026

Microstructure-controlled vortex phases and two-phase superconductivity in (TaNb)0.7(HfZrTi)0.5 revealed by ac magnetostrictive coefficients

We investigate flux dynamics in the high-entropy alloy superconductor (TaNb)0.7(HfZrTi)0.5 after annealing (as-cast, 500 {\deg}C, 550 {\deg}C, and 1000 {\deg}C) using a sensitive ac composite magnetoelectric method that measures the complex ac magnetostrictive coefficient (d{\lambda}/dH)ac. The resulting vortex phase diagrams show that intermediate annealing (500-550 {\deg}C) induces nanoscale clustering, enhances pinning, and produces a pronounced fishtail effect with successive elastic- and plastic-vortex-glass regimes. Flux-jump instabilities appear at 550 {\deg}C and persist at 1000 {\deg}C, indicating strong pinning and thermomagnetic instability in the low-temperature, low-field regime. Remarkably, the 1000 {\deg}C sample exhibits a two-step superconducting response-a double plateau or drop in d{\lambda}'/dH and two dissipation peaks in d{\lambda}''/dH-demonstrating the coexistence of two superconducting phases with distinct irreversibility and critical-field value. We further show that the resolvability of the two-step (d{\lambda}/dH)ac signature is governed by the topological connectivity of the phase-separated microstructure, which controls magnetic shielding between the TaNb-rich network and the (TaNb)0.7(HfZrTi)0.5 parent phase. These results establish a direct microstructure-vortex-state correlation and provide a route to tailoring flux pinning in chemically complex superconductors via thermal processing.

cond-mat.supr-con↗

arXiv2025

Anomalous Hall effect in antiferromagnetic RGaGe (R = Nd, Gd) single crystals

Recently, the non-centrosymmetric Weyl semimetallic candidate family RTX (R = rare-earth element, T= poor metal, X = Si and Ge) has recently attracted significant attention due to its exotic quantum states and potential applications in quantum devices. In this study, our comprehensive investigations of high-quality NdGaGe and GdGaGe single crystals reveal distinct magnetic and electrical responses. Both compounds exhibit antiferromagnetic transitions with TN - 7.6 K and 22.4 K for NdGaGe and GdGaGe, respectively. NdGaGe exhibits strong magnetic anisotropy (\c{hi}c /\c{hi}a - 70). In contrast, GdGaGe displays weak magnetic anisotropic behavior (\c{hi}c /\c{hi}a - 1) with a distinctive spin-flop transition. Below TN, NdGaGe shows significant negative magnetoresistance due to the reduced spin-disorder scattering arising from the field-induced spin alignment. GdGaGe exhibits more complex magnetoresistance behavior: positive values at low fields transitioning to negative values attributed to the reduced spin-flop scattering. Specially, NdGaGe demonstrates a large anomalous Hall conductance (AHC) of approximately 368 {\Omega}-1 cm-1, which is dominated by the intrinsic mechanism. These reveal the pivotal role of rare-earth elements in modulating the electronic structure, magnetic properties, and transport characteristics of the RGaGe system, thereby providing valuable insights for developing next-generation spintronic devices.

cond-mat.supr-con↗