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Shuxiang Yang

Publications and source records attributed to Shuxiang Yang.

11 recordsLinked to original sources
arXiv2025

Robust Longitudinal-lateral Look-ahead Pursuit Path-Following Control: Fast Finite-Time Stability Guarantee

This paper addresses the challenging problem of robust path-following for fixed-wing unmanned aerial vehicles (UAVs) in complex environments with bounded external disturbances and non-smooth predefined paths. Due to the unique aerodynamic characteristics and flight constraints of fixed-wing UAVs, achieving accurate and fast stable path following remains difficult, especially in low-altitude mountainous terrains, urban landscapes, and under wind disturbances. Most existing path-following guidance laws often struggle to ensure fast stabilization under unknown bounded disturbances while maintaining sufficient robustness, and there is a lack of research on optimizing robustness for non-smooth paths under flight constraints. This paper addresses these issues by proposing a constraints-based robust path-following controller. Firstly, from the perspective of global random attractor, we innovatively introduce robustness metrics that quantify both the exponential convergence rate and the range of the ultimate attractor set. Secondly, building on these metrics, we develop a robust longitudinal-lateral look-ahead pursuit (RLLP) guidance law for fixed-wing UAVs, specifically considering the flight path angle and track angle under external disturbances. Thirdly, we also derive an optimized version (Optimal-RLLP) to enhance the robustness metrics, and elaborate on the sufficient conditions for fast finite-time stability, ensuring the guidance law achieves finite-time stability and robustness with reduced sensitivity to constrained uncertainties. The simulation results validate the proposed guidance law's feasibility, optimality and robustness under atmospheric disturbances using a high-fidelity simulation platform and provide key principle for practical deployment.

eess.SY↗
arXiv2025

Selective Kondo screening and strange metallicity by sliding Dirac semimetals

Kondo screening of local moments in normal metals typically leads to hybridized conduction and valence bands separated by a Kondo gap, resulting in an insulating state at half-band filling. We show a dramatic change of this scenario in a Dirac-semimetal-based correlated system -- a bilayer honeycomb lattice heterostructure where a local moment lattice is stacked on a Dirac semimetal breaking the inversion symmetry. This system is modeled by an extended Anderson honeycomb lattice involving the real-space dependence of major interlayer hybridization parameters on the relative sliding distance along the armchair direction. First, we unveil multiple Kondo scales and successive Kondo breakdown transitions in this correlated heterostructure under sliding. Second, we demonstrate the existence of a genuine selective Kondo screening phase which is stabilized near the A-B stack pattern and is accessible by applying interlayer voltage. Third, we find a nearly flat hybridized band located concomitantly within the Kondo gap, resulting in an unprecedented metallic state at half-band filling. This unconventional heavy fermion state is characterized by violation of Luttinger theorem and appearance of a Van Hove singularity at the Fermi energy. The general sliding-driven band structure landscape and the implications of our results for the broad context of multiorbital Kondo physics are briefly discussed.

cond-mat.str-el↗
arXiv2024

Discovery of superconductivity in technetium-borides at moderate pressures

Advances in theoretical calculations boosted the searches for high temperature superconductors, such as sulfur hydrides and rare-earth polyhydrides. However, the required extremely high pressures for stabilizing these superconductors handicapped further implementations. Based upon thorough structural searches, we identified series of unprecedented superconducting technetium-borides at moderate pressures, including TcB (P6$_3$/mmc) with superconducting transition temperature $T_{\text{c}}$ = 20.2 K at ambient pressure and TcB$_2$ (P6/mmm) with $T_{\text{c}}$ = 23.1 K at 20 GPa. Superconductivity in these technetium-borides mainly originates from the coupling between the low frequency vibrations of technetium-atoms and the dominant technetium-4d electrons at the Fermi level. Our works therefore present a fresh group in the family of superconducting borides, whose diversified crystal structures suggest rich possibilities in discovery of other superconducting transition-metal-borides.

cond-mat.supr-con↗
arXiv2023

Leading components and pressure-induced color changes in N-doped lutetium hydride

Recent experimental study by Dias {\it et al.} claims to have discovered room-temperature superconductivity in lutetium-nitrogen-hydrogen system at 1 GPa [Nature 615, 244 (2023)], which sheds light on the long-held dream of ambient superconductivity. However, all follow-up experiments found no evidence of superconductivity. The compositions and the crystal structures of the lutetium-nitrogen-hydrogen system remain unknown. By employing the density functional theory based structure prediction algorithm, we suggest that in lutetium-nitrogen-hydrogen the major component is LuH$_2$ (Fm$\bar{3}$m), together with minor LuN (Fm$\bar{3}$m). The blue LuH$_2$ at ambient pressure will turn into purple and red color at higher pressures, possibly accompanied by the formation of vacancies at hydrogen-sites. In LuH$_2$ and LuN, the density of states at the Fermi level is dominated by the Lu-5d orbitals, while those from hydrogen and nitrogen are very small, leading to the absence of superconductivity in these two compounds. Nitrogen-doping to LuH$_2$ fails to enhance the superconductivity as well. In this work, we identify the leading components in N-doped lutetium hydride, explain its intriguing color changes under pressure, and elucidate why superconductivity is absent in the follow-up experiments.

cond-mat.supr-con↗
arXiv2023

Dynamics of the Geometric Phase in Inhomogeneous Quantum Spin Chains

The dynamics of the geometric phase are studied in inhomogeneous quantum spin chains after a quench. Analytic expressions of the Pancharatnam geometric phase (PGP) $\mathcal{G}(t)$ are derived, for both the period-two quantum Ising chain (QIC) and the disordered QIC. In the period-two QIC, due to the periodic modulation, the PGP changes with time at the boundary of the Brillouin zone, and consequently, the winding number $ν_{D}(t)=\int_{0}^π[\partialϕ_{k}^{G}(t)/\partial k]dk/2π$ based on the PGP is not quantized and thus not topological anymore. Nevertheless, the PGP and its winding number show non-analytic singularities at the critical times of the dynamical quantum phase transitions (DQPTs). This relation between the PGP and the DQPT is further confirmed in the disordered QIC, where the winding number is not defined. It is found that the critical time of DQPT inherited from the homogeneous system and the additional one induced by the weak disorder are also accompanied by the non-analytic singularity of the PGP, by decomposing the PGP into each quasiparticle mode. The connection between the non-analytic behavior of the PGP at the critical time and the DQPT, regardless of whether the winding number is topological, can be explained by the fact that they both arise when the Loschmidt amplitude vanishes.

cond-mat.dis-nn↗
arXiv2019

Periodic Anderson model with Holstein phonons for the description of the Cerium volume collapse

Recent experiments have suggested that the electron-phonon coupling may play an important role in the $γ\rightarrow α$ volume collapse transition in Cerium. A minimal model for the description of such transition is the periodic Anderson model. In order to better understand the effect of the electron-phonon interaction on the volume collapse transition, we study the periodic Anderson model with coupling between Holstein phonons and electrons in the conduction band. We find that the electron-phonon coupling enhances the volume collapse, which is consistent with experiments in Cerium. While we start with the Kondo Volume Collapse scenario in mind, our results capture some interesting features of the Mott scenario, such as a gap in the conduction electron spectra which grows with the effective electron-phonon coupling.

cond-mat.str-el↗
arXiv2015

Cooling Atomic Gases With Disorder

Cold atomic gases have proven capable of emulating a number of fundamental condensed matter phenomena including Bose-Einstein condensation, the Mott transition, Fulde-Ferrell-Larkin-Ovchinnikov pairing and the quantum Hall effect. Cooling to a low enough temperature to explore magnetism and exotic superconductivity in lattices of fermionic atoms remains a challenge. We propose a method to produce a low temperature gas by preparing it in a disordered potential and following a constant entropy trajectory to deliver the gas into a non-disordered state which exhibits these incompletely understood phases. We show, using quantum Monte Carlo simulations, that we can approach the Neél temperature of the three-dimensional Hubbard model for experimentally achievable parameters. Recent experimental estimates suggest the randomness required lies in a regime where atom transport and equilibration are still robust.

cond-mat.quant-gas↗
arXiv2013

Unconventional superconductivity on the triangular lattice Hubbard model

Using large-scale dynamical cluster quantum Monte Carlo simulations, we explore the unconventional superconductivity in the hole-doped Hubbard model on the triangular lattice. Due to the interplay of electronic correlations, geometric frustration, and Fermi surface topology, we find a doubly degenerate singlet pairing state at an interaction strength close to the bare bandwidth. Such an unconventional superconducting state is mediated by antiferromagnetic spin fluctuations along the $Γ$-$K$ direction, where the Fermi surface is nested. An exact decomposition of the irreducible particle-particle vertex further confirms the dominant component of the effective pairing interaction comes from the spin channel. Our findings provide support for chiral $d +i d$ superconductivity in water-intercalated sodium cobaltates Na$_{x}$CoO$_{2} \cdot y$H$_{2}$O, as well as insight into the superconducting phases of the organic compounds $κ$-(ET)$_{2}$X and Pd(dmit)$_{2}$.

cond-mat.str-el↗
arXiv2012

Impurity Quantum Phase Transition in a Current-Carrying d-Wave Superconductor

We study an Anderson impurity embedded in a d-wave superconductor carrying a supercurrent. The low-energy impurity behavior is investigated by using the numerical renormalization group method developed for arbitrary electronic bath spectra. The results explicitly show that the local impurity state is completely screened upon the non-zero current intensity. The impurity quantum criticality is in accordance with the well-known Kosterlitz-Thouless transition.

cond-mat.str-el↗
arXiv2011

The response to dynamical modulation of the optical lattice for fermions in the Hubbard model

Fermionic atoms in a periodic optical lattice provide a realization of the single-band Hubbard model. Using Quantum Monte Carlo simulations along with the Maximum Entropy Method, we evaluate the effect of a time-dependent perturbative modulation of the optical lattice amplitude on atomic correlations, revealed in the fraction of doubly-occupied sites. Our treatment extends previous approaches which neglected the time dependence of the on-site interaction, and shows that this term changes the results in a quantitatively significant way. The effect of modulation depends strongly on the filling-- the response of the double occupation is significantly different in the half-filled Mott insulator from the doped Fermi liquid region.

cond-mat.quant-gas↗