Characterizing the energy gap and demonstrating an adiabatic quench in an interacting spin system

TL;DR

This paper measures the energy gap of amplitude excitations in a spin-1 condensate during a quantum phase transition, demonstrating an adiabatic quench and advancing understanding of non-equilibrium dynamics and entanglement generation.

Contribution

It provides the first characterization of amplitude excitation gaps in a spin-1 condensate and demonstrates an adiabatic quench through a quantum phase transition.

Findings

Measured the energy gap of amplitude excitations across phases.

Confirmed finite size effects lead to a non-zero gap at the critical point.

Demonstrated an adiabatic quench through the phase transition.

Abstract

Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. It gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase/amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal non-equilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure their energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite size effects lead to a non-zero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.