Quantum phases from competing short- and long-range interactions in an optical lattice

TL;DR

This paper experimentally demonstrates a quantum many-body system with competing short- and long-range interactions, revealing four distinct phases and a first-order phase transition, advancing quantum simulation capabilities.

Contribution

It introduces a novel bosonic lattice model with tunable short- and infinite-range interactions, observing multiple quantum phases and real-time phase transition dynamics.

Findings

Observation of superfluid, supersolid, Mott insulator, and charge density wave phases.

Real-time detection of a first-order phase transition.

Controlled competition between short- and long-range interactions.

Abstract

Insights into complex phenomena in quantum matter can be gained from simulation experiments with ultracold atoms, especially in cases where theoretical characterization is challenging. However these experiments are mostly limited to short-range collisional interactions. Recently observed perturbative effects of long-range interactions were too weak to reach novel quantum phases. Here we experimentally realize a bosonic lattice model with competing short- and infinite-range interactions, and observe the appearance of four distinct phases - a superfluid, a supersolid, a Mott insulator and a charge density wave. Our system is based on an atomic quantum gas trapped in an optical lattice inside a high finesse optical cavity. The strength of the short-ranged on-site interactions is controlled by means of the optical lattice depth. The infinite-range interaction potential is mediated by a vacuum mode of the cavity and is independently controlled by tuning the cavity resonance. When probing the phase transition between the Mott insulator and the charge density wave in real-time, we discovered a behaviour characteristic of a first order phase transition. Our measurements have accessed a regime for quantum simulation of many-body systems, where the physics is determined by the intricate competition between two different types of interactions and the zero point motion of the particles.