Nonlinear quantum Kibble-Zurek ramps in open systems at finite temperature

TL;DR

This paper investigates how nonlinear ramps of temperature and Hamiltonian parameters in open quantum systems can reveal the universality class of quantum phase transitions at zero temperature, even at finite temperature.

Contribution

It introduces a method to probe quantum critical exponents in open systems during nonlinear ramps, highlighting conditions that suppress subleading corrections for experimental relevance.

Findings

Nonlinear ramps can reveal quantum critical universality at finite temperature.

Identification of specific ramps that suppress subleading corrections.

Open-system dynamics influence excitation density in non-trivial ways.

Abstract

We analyze quantum systems under a broad class of protocols in which the temperature and a Hamiltonian control parameter are ramped simultaneously and, in general, in a nonlinear fashion toward a quantum critical point. Using an open-system version of a Kitaev quantum wire as an example, we show that, unlike finite-temperature protocols at fixed temperature, these protocols allow us to probe, in an out-of-equilibrium situation and at finite temperature, the universality class (characterized by the critical exponents $\nu$ and $z$) of an equilibrium quantum phase transition at zero temperature. Key to this is the identification of ramps in which both coherent and incoherent parts of the open-system dynamics affect the excitation density in a non-negligible way. We also identify the specific ramps for which subleading corrections to the asymptotic scaling laws are suppressed, which serves as a guide to dynamically probing quantum critical exponents in experimentally realistic finite-temperature situations.