First-order transitions in spin chains coupled to quantum baths

TL;DR

This paper demonstrates how engineered quantum baths can alter the nature of phase transitions in spin chains, inducing first-order transitions and revealing effects relevant for quantum sensing and simulation.

Contribution

It introduces a method to control phase transition order in spin chains via tailored quantum baths, combining quantum Monte Carlo and mean-field approaches.

Findings

Quantum baths can induce first-order transitions in spin chains.

Dissipation creates an effective magnetic field affecting magnetization.

Results are applicable to quantum simulators and sensing technologies.

Abstract

We show that tailoring the dissipative environment allows to change the features of continuous quantum phase transitions and, even, induce first order transitions in ferromagnetic spin chains. In particular, using a numerically exact quantum Monte Carlo method for the paradigmatic Ising chain of one-half spins in a transverse magnetic field, we find that spin couplings to local quantum boson baths in the Ohmic regime can drive the transition from the second to the first order even for a low dissipation strength. Moreover, using a variational mean-field approach for the treatment of spin-spin and spin-boson interactions, we point out that phase discontinuities are ascribable to a dissipation induced effective magnetic field which is intrinsically related to the bath quantum fluctuations and vanishes for classical baths. The effective field is able to switch the sign of the magnetization along the direction of spin-spin interactions. The results can be potentially tested in recent quantum simulators and are relevant for quantum sensing since the spin system could not only detect the properties of non-classical baths, but also the effects of weak magnetic fields.