Open positions for a Postdoctoral Research Associate and a PhD studentship.

Introduction

The project aims to realize supersolid and droplet phases of matter in a laser-driven Bose-Einstein condensate of ultracold Cs atoms via light-mediated interactions introduced by feed-back from a retroreflecting mirror. Diffractive dephasing of the retroreflected light induces the nontrivial spatial correlations leading to supersolidity. This work will develop a unique platform for exploring emergent behaviour and symmetry-breaking in self-organised supersolids. We will investigate 1D and 2D supersolids, including those with novel quasiperiodic symmetries. We will study quantum droplets and their connection to solitons. Investigations of persistent temporal dynamics will provide a fruitful connection to the archetypical quantum Hamiltonian Mean Field Model advancing the knowledge of the statistical mechanics of long-range coupled systems and time crystals.

It builds on earlier work on self-organized phases in laser-cooled atomic ensembles and vapour cells in single-mirror feedback setups. For an explanation of how diffraction and the Talbot-effect mediate light-induced interaction between atoms, see the overview and this review.

A schematic experimental implementation is shown below. A cloud of Cs atoms is trapped in the shape of a cigar or pancake in a vacuum chamber (dashed black lines). An afocal telescope is used to relay the feedback mirror from outside the vacuum chamber as a virtual mirror close to the cloud (dashed red lines). Expected supersolid structures in 1D are stripes, in 2D hexagons. In the space between the lenses additional elements as spatial filters or image rotating Dove prisms can be introduced to control the properties and symmetry of the crytalline structures, in particular to induce quasi-periodic ones. The spatial light modulator (SLM) will be realized as a liquid crystal on silicon modulator (LCOS-SLM) or a digital mirror device (DMD) depending on switching speed and phase and amplitude smoothness required. This will be used either to seed the stationary ground state of the supersolid directly or an oscillating “quasi-stationary” states which a very long lifetime due to long-range coupling. The apparatus builds on an existing experimental platform for quantum-degenerate ensembles of caesium atoms, used to study lattice physics, nonlinear quantum fluids, and out-of-equilibrium many-body dynamics.

• Prof. Thorsten Ackemann (lead)
• Dr. Elmar Haller (co-lead)
• Dr. Gordon Robb (co-lead)
• Dr. Peter Kirton (co-lead)
• Mr. Kelsey O’Donnel

• EPSRC: Supersolids and quantum droplets via light mediated interactions (10/2025 - 09/2028, £1M, FEC £1.26M)