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.

• 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)