Dynamical Quasicondensation of Hard-Core Bosons at Finite Momenta

TL;DR

This study experimentally demonstrates the formation of finite-momentum quasicondensates in a far-from-equilibrium system of strongly-interacting bosons, revealing novel phase order distinct from ground states.

Contribution

It reports the first observation of dynamical quasicondensation at finite momenta in a non-equilibrium setting of hard-core bosons.

Findings

Observation of coherence emergence after a quench

Formation of quasicondensates at finite momenta

Distinct phase order from ground-state configurations

Abstract

Long-range order in quantum many-body systems is usually associated with equilibrium situations. Here, we experimentally investigate the quasicondensation of strongly-interacting bosons at finite momenta in a far-from-equilibrium case. We prepare an inhomogeneous initial state consisting of one-dimensional Mott insulators in the center of otherwise empty one-dimensional chains in an optical lattice with a lattice constant $d$. After suddenly quenching the trapping potential to zero, we observe the onset of coherence in spontaneously forming quasicondensates in the lattice. Remarkably, the emerging phase order differs from the ground-state order and is characterized by peaks at finite momenta $\pm (\pi/2) (\hbar / d)$ in the momentum distribution function.