On the phase structure of driven quantum systems

Driven quantum coarsening

We study the driven dynamics of quantum coarsening. We analyze models of M-component rotors coupled to two electronic reservoirs at different chemical potentials that generate a current threading through the system. In the large M limit we derive the dynamical phase diagram as a function of temperature, strength of quantum fluctuations, voltage and coupling to the leads. We show that the slow relaxation in the ordering phase is universal. On large time and length scales the dynamics are analogous to stochastic classical ones, even for the quantum system driven out of equilibrium at zero temper…

Driven Disordered Periodic Media with an Underlying Structural Phase Transition

We investigate the driven states of a two-dimensional crystal whose ground state can be tuned through a square-triangular transition. The depinning of such a system from a quenched random background potential occurs via a complex sequence of dynamical states, which include plastic flow states, hexatics, dynamically stabilized triangle and square phases and intermediate regimes of phase coexistence. These results are relevant to transport experiments in the mixed phase of several superconductors which exhibit such structural transitions as well as to driven colloidal systems whose interactions …

Quantized frequency-domain polarization of driven phases of matter

Periodically driven quantum systems can realize novel phases of matter that do not exist in static settings. We study signatures of these drive-induced phases on the $(d+1)$-dimensional Floquet lattice, comprised of $d$ spatial dimensions plus the frequency domain. The average position of Floquet eigenstates along the frequency axis can be written in terms of a non-adiabatic Berry phase, which we interpret as frequency-domain polarization. We argue that whenever this polarization is quantized to a nontrivial value, the phase of matter cannot be continuously connected to a time-independent stat…

Floquet Time Spirals and Stable Discrete Time Quasi-Crystals in Quasi-Periodically Driven Quantum Many-Body Systems

We analyse quasi-periodically driven quantum systems that can be mapped exactly to periodically driven ones and find Floquet Time Spirals in analogy with spatially incommensurate spiral magnetic states. Generalising the mechanism to many-body systems we discover that a form of discrete time-translation symmetry breaking can also occur in quasi-periodically driven systems. We construct a discrete time quasi-crystal stabilised by many-body localisation. Crucially, it persists also under perturbations that break the equivalence with periodic systems. As such it provides evidence of a stable quasi…

自旋玻璃海绵中的驱动与非驱动表面混沌

Driven and Non-Driven Surface Chaos in Spin-Glass Sponges

该研究用重整化群理论分析 d=3 自旋玻璃系统的光滑与分形表面，揭示海绵结构中的独立表面有序相、三相点及不同混沌轨迹和指数。

Unconventional scaling theory in disorder-driven quantum phase transition

We clarify novel forms of scaling functions of conductance, critical conductance distribution and localization length in a disorder-driven quantum phase transition between band insulator and Weyl semimetal phases. Quantum criticality of the phase transition is controlled by a clean-limit fixed point with spatially anisotropic scale invariance. We argue that the anisotropic scale invariance is reflected on unconventional scaling function forms in the quantum phase transition. We verify the proposed scaling function forms in terms of transfer-matrix calculations of conductance and localization l…