arXiv subjects

Weiwei Dong

Publications and source records attributed to Weiwei Dong.

5 recordsLinked to original sources

arXiv2026

Bragg-Williams order competes with superconductivity

Orderings in charge and spin have been extensively studied to unravel their correlation to emergent superconductivity over the past decades. Bragg-Williams order (BWO), a classical structural order parameter describing site occupancy in alloys, has long been speculated to influence superconducting behavior. Yet, its role still remains ambiguous, largely due to the difficulty of isolating BWO from concomitant charge doping or competing electronic instabilities. Here, we establish In2/3PSe3 as a platform wherein indium vacancies are reversibly configurable between ordered and disordered states via thermal treatment. We show that the disordered phase undergoes a pressure-induced superconducting transition with a Tc of 11 K, significantly higher than the 7 K observed in its ordered counterpart. This constitutes a rare instance in which pure BWO variation drives a substantial shift in Tc. By combining a Ginzburg-Landau phenomenological analysis with a BCS-McMillan microscopic description, we demonstrate that BWO naturally suppresses superconductivity through electron-phonon interactions, a mechanism supported by ultra-low-wavenumber Raman measurements. Our findings support BWO as an independent order parameter that competes directly with superconductivity, extending the concept of competing orders beyond conventional electronic and magnetic degrees of freedom.

cond-mat.supr-con↗

arXiv2024

High entropy alloys and their affinity to hydrogen: from Cantor to platinum group elements alloys

Properties of high entropy alloys are currently in the spotlight due to their promising applications. One of the least investigated aspects is the affinity of these alloys to hydrogen, its diffusion and reactions. In this study we apply high-pressure at ambient temperature and investigate stress-induced diffusion of hydrogen into the tructure of high entropy alloys HEA including the famous Cantor alloy as well as less known, but nevertheless important platinum group PGM alloys. By applying X-ray diffraction to samples loaded into diamond anvil cells we perform a comparative investigation of these HEA alloys in Ne and H2 pressure-transmitting media. Surprisingly, even under stresses far exceeding conventional industrial processes both Cantor and PGM alloys show exceptional resistance to hydride formation, on par with widely used industrial grade CuBe alloys. Our observations inspire optimism for practical HEA applications in hydrogen-relevant industry and technology e.g. coatings, etc, particularly those related to transport and storage.

cond-mat.mtrl-sci↗

arXiv2021

Fe0.79Si0.07B0.14 metallic glass gaskets for high-pressure research beyond 1 Mbar

A gasket is an important constituent of a diamond anvil cell (DAC) assembly, responsible for the sample chamber stability at extreme conditions for x-ray diffraction studies. In this work, we studied the performance of gaskets made of metallic glass Fe0.79Si0.07B0.14 in a number of high-pressure x-ray diffraction (XRD) experiments in DACs equipped with conventional and toroidal-shape diamond anvils. The experiments were conducted in either uniaxial or radial geometry with x-ray beams of micron to sub-micron size. We report that the Fe0.79Si0.07B0.14 metallic glass gaskets offered stable sample environment under compression exceeding one megabar in all XRD experiments described here, even in those involving inter- or small-molecule gases (e.g. Ne, H2) used as pressure transmitting media or in those with laser heating in a DAC. These emphasize the material's importance for a great number of delicate experiments conducted under extreme conditions. Our results indicate that the application of Fe0.79Si0.07B0.14 metallic glass gaskets in XRD experiments of both uniaxial and radial geometries substantially improves the signal-to-noise ratio in comparison to that with conventional gaskets made of Re, W, steel or other crystalline metals.

cond-mat.mtrl-sci↗

arXiv2017

Bipartite entanglement in AJL's algorithm for three-strand braids

Aharonov, Jones, and Landau [Algorithmica 55, 395 (2009)] have presented a polynomial quantum algorithm for approximating the Jones polynomial. We investigate the bipartite entanglement properties in AJL's algorithm for three-strand braids. We re-describe AJL's algorithm as an equivalent algorithm which involves three work qubits in some mixed state coupled to a single control qubit. Furthermore, we use the Peres entanglement criterion to study the entanglement features of the state before measurements present in the re-described algorithm for all bipartitions. We show that the state is a product state relative to the bipartition between the first work qubit and the others. And it has no entanglement between the control qubit and work ones. We also prove a sufficient and necessary condition for its entanglement between the second (third) work qubit and the others. Moreover, we discuss the relation between its bipartite entanglement and elementary crossings in the three-strand braid group. We find that braids whose trace closures are topologically identical may have different entanglement properties in AJL's algorithm.

quant-ph↗

arXiv2017

Urban Rail Transit System Operation Optimization A Game Theoretical Methodology

The Urban Rail Transit (URT) has been one of the major trip modes in cities worldwide. As the passengers arrive at variable rates in different time slots, e.g., rush and non-rush hours, the departure frequency at a site directly relates to perceived service quality of passengers; the high departure frequency, however, incurs more operation cost to URT. Therefore, a tradeoff between the interest of railway operator and the service quality of passengers needs to be addressed. In this paper, we develop a model on the operation method of train operation scheduling using a Stackelberg game model. The railway operator is modeled as the game leader and the passengers as the game follower, and an optimal departure frequency can be determine the tradeoff between passengers' service quality and operation cost. We present several numerical examples based on the operation data from Nanjing transit subway at China. The results demonstrate that the proposed model can significantly improve the traffic efficiency.

cs.GT↗