Quantum quench in 2D using the variational Baeriswyl wavefunction

TL;DR

This paper introduces a variational approach combining the Baeriswyl wavefunction with dynamical principles to study quantum quenches in 2D spinless fermions, revealing regimes of oscillation and thermalization.

Contribution

It develops a novel non-equilibrium formalism for 2D fermionic systems using the Baeriswyl wavefunction, bridging variational methods with quantum quench dynamics.

Findings

Variational results match exact simulations for ground state and short-time dynamics.

System exhibits undamped oscillations or relaxation depending on interaction parameters.

Order parameter behavior indicates signs of thermalization in non-integrable systems.

Abstract

By combining the Baeriswyl wavefunction with equilibrium and time-dependent variational principles, we develop a non-equilibrium formalism to study quantum quenches for two dimensional spinless fermions with nearest-neighbour hopping and repulsion. The variational ground state energy and the short time dynamics agree convincingly with the results of numerically exact simulations. We find that depending on the initial and final interaction strength, the quenched system either exhibits undamped oscillations or relaxes to a time independent steady state. The time averaged expectation value of the CDW order parameter rises sharply when crossing from the steady state regime to the oscillating regime, indicating that the system, being non-integrable, shows signs of thermalization with an effective temperature above or below the equilibrium critical temperature, respectively.