arXiv subjects

Xiaolong Yao

Publications and source records attributed to Xiaolong Yao.

4 recordsLinked to original sources

arXiv2026

Orthogonal Attosecond Control of Solid-State Harmonics by Optical Waveforms and Quantum Geometry Engineering

High-harmonic generation (HHG) in two-dimensional materials offers a compelling route toward compact extreme ultraviolet sources and probing electron dynamics on the attosecond scale. However, achieving precise control over the emission and disentangling the complex interplay between intraband and interband quantum pathways remains a central challenge. Here, we demonstrate through first-principles simulations that HHG in monolayer WS2 can be subjected to precise, complementary control by combining all-optical two-color laser fields with mechanical strain engineering. This dual-mode strategy provides distinct, orthogonal control over harmonic yield, polarization, and spectral features. We reveal that sculpting the two-color field's relative phase provides a sub-femtosecond switch for the quantum coherence of electron-hole pairs, thereby optimizing harmonic emission. Crucially, we uncover that tensile strain modulates the total harmonic yield and specifically amplifies the perpendicular harmonic component by nearly a factor of two. This enhancement arises through a dual mechanism - while strain-modified band dispersion enhances the intraband current, a significant reshaping of the Berry curvature (BC) substantially increases the anomalous velocity contribution to the interband response. This quantum geometric effect manifests as a robust, monotonic dependence of the harmonic yield on strain and a significant amplification of the perpendicularly polarized harmonics, providing a clear experimental signature for probing quantum geometric effects. Our findings establish a versatile framework for optimizing solid-state HHG and introduce a powerful all-optical method to map strain and quantum geometric properties of materials, positioning monolayer WS2 as a model system for exploring attosecond physics at the nexus of bulk and atomic scales.

physics.comp-ph↗

arXiv2025

Distortion-Driven Carrier Decoupling in Doped LiMgPO4

The interplay between lattice distortions and charge carriers governs the properties of many functional oxides. In alkali-doped LiMgPO4, a significant enhancement in dosimetric response is observed, but its microscopic origin is not understood. Using non-adiabatic molecular dynamics, we reveal a fundamental mechanism of carrier decoupling driven by a hierarchy of lattice distortions. We show that electrons localize into stable small polarons on an ultrafast timescale, trapped by the strong local potential induced by the dopant, while holes form more delocalized polarons that migrate efficiently through a lattice smoothed by global strain. The stark contrast between the dynamics of trapped electrons and mobile holes explains the suppressed recombination and enhanced energy storage. These results present a clear physical picture of how multiscale lattice distortions can independently control electron and hole transport, offering new insights into the physics of polarons in complex materials.

cond-mat.mtrl-sci↗

arXiv2025

First-principles design of stable spin qubits in monolayer MoS$_2$ with elemental defect engineering

Quantum information science (QIS), encompassing technologies such as quantum computing, sensing, and communication, relies on the development and manipulation of quantum bits (qubits). Recently, two-dimensional (2D) materials -- characterized by their atomic thinness and external controllability -- have emerged as promising candidates for qubit fabrication and manipulation at room temperature. In this study, we propose that antisite defects (MX) in 2D transition metal disulfides (TMDs) can serve as tunable quantum defects with controlled positioning. Using first-principles atomic structure simulations, we identify six thermodynamically stable neutral antisite defects (MX, where M = Mg, Ca, Sr, Ba, Zn, Cd; X = S) in monolayer 1H-MoS$_2$. These defects exhibit potential as spin-defected qubits with stable triplet ground states. Additionally, we demonstrate that the reduction of the bandgap leads to significant fluctuations in the absorption coefficient within the low-energy range, resulting in the optical response within the desired telecommunication band, which is advantageous for quantum communication applications. The zero-phonon line (ZPL) associated with these qubits can serve as an effective identifier. This work presents the novel, tunable approach to exploiting defects in 2D materials, opening new possibilities for the development of qubit platforms in quantum information technology.

physics.app-ph↗

arXiv2020

Real-time ab initio simulation of inelastic electron scattering using the exact, density functional, and alternative approaches

To investigate inelastic electron scattering, which is ubiquitous in various fields of study, we carry out ab initio study of the real-time dynamics of a one-dimensional electron wave packet scattered by a hydrogen atom using different methods: the exact solution, the solution provided by time-dependent density functional theory (TDDFT), and the solutions given by alternative approaches. This research not only sheds light on inelastic scattering processes but also verifies the capability of TDDFT in describing inelastic electron scattering. We revisit the adiabatic local-density approximation (ALDA) in describing the excitation of the target during the scattering process along with a self-interaction correction and spin-polarized calculations. Our results reveal that the ALDA severely underestimates the energy transferred in the regime of low incident energy particularly for a spin-singlet system. After demonstrating alternative approaches, we propose a hybrid ab initio method to deal with the kinetic correlation alongside TDDFT. This hybrid method would facilitate first-principles studies of systems in which the correlation of a few electrons among many others is of interest.

physics.atom-ph↗