# Symmetry breaking bias and the dynamics of a quantum phase transition

## TL;DR

This paper investigates how a small symmetry-breaking bias can restore adiabaticity during a quantum phase transition, challenging the traditional view of defect formation predicted by the Kibble-Zurek mechanism.

## Contribution

It introduces a scaling law for the minimal bias needed to maintain adiabaticity, supported by DMRG simulations of the quantum Ising chain.

## Key findings

- Tiny symmetry-breaking bias can prevent defect formation.
- The minimal bias scales with quench time according to a specific power law.
- Results are applicable to ultracold Rydberg atom experiments.

## Abstract

The Kibble-Zurek mechanism predicts the formation of topological defects and other excitations that quantify how much a quantum system driven across a quantum critical point fails to be adiabatic. We point out that, thanks to the divergent linear susceptibility at the critical point, even a tiny symmetry breaking bias can restore the adiabaticity. The minimal required bias scales like $\tau_Q^{-\beta\delta/(1+z\nu)}$, where $\beta,\delta,z,\nu$ are the critical exponents and $\tau_Q$ is a quench time. We test this prediction by DMRG simulations of the quantum Ising chain. It is directly applicable to the recent emulation of quantum phase transition dynamics in the Ising chain with ultracold Rydberg atoms.