Dynamical Quantum Phase Transitions in presence of a spin bath

TL;DR

This paper derives an effective Hamiltonian for a transverse Ising model coupled to a spin bath under high-frequency AC magnetic fields, showing tunability of quantum phase transitions and analyzing phase diagrams for specific materials.

Contribution

It introduces a method to suppress spin blocking in quantum phase transitions using AC fields and provides phase diagrams for spin 7/2 nuclei in relevant materials.

Findings

AC field suppresses spin blocking mechanism

Quantum critical point can be tuned via AC magnetic field

Phase diagram calculated for LiHo_xY_{1-x}F_4 system

Abstract

We derive an effective time independent Hamiltonian for the transverse Ising model coupled to a spin bath, in the presence of a high frequency AC magnetic field. We show that the spin blocking mechanism that removes the quantum phase transition can be suppressed by the AC field, allowing high tunability of the quantum critical point. Finally, we calculate the phase diagram within the RPA approximation for the case of spin $7/2$ nuclei, appropriate to the $LiHo_{x}Y_{1-x}F_{4}$ system.