Bloch oscillations in the absence of a lattice

TL;DR

This paper demonstrates that an impurity in a strongly interacting 1D Bose liquid exhibits Bloch oscillations and Bragg reflections due to emergent order, despite the absence of a physical lattice.

Contribution

It reveals that Bloch oscillations can occur in a translationally invariant quantum liquid due to emergent crystalline order and kinematic constraints, supported by experimental and numerical evidence.

Findings

Impurity momentum shows Bragg reflections at an emergent Brillouin zone edge.

Impurity exhibits periodic Bloch oscillations without a lattice.

Experimental results align with large-scale numerical simulations.

Abstract

We experimentally investigate the quantum motion of an impurity atom that is immersed in a strongly interacting one-dimensional Bose liquid and is subject to an external force. We find that the momentum distribution of the impurity exhibits characteristic Bragg reflections at the edge of an emergent Brillouin zone. While Bragg reflections are typically associated with lattice structures, in our strongly correlated quantum liquid they result from the interplay of short-range crystalline order and kinematic constraints on the many-body scattering processes in the one-dimensional system. As a consequence, the impurity exhibits periodic dynamics that we interpret as Bloch oscillations, which arise even though the quantum liquid is translationally invariant. Our observations are supported by large-scale numerical simulations.