Ultracold caesium atoms trapped in laser light will spontaneously arrange themselves into a supersolid—a paradoxical state that flows without friction while maintaining a crystal-like structure. This project addresses a fundamental gap: although supersolids were predicted decades ago in helium and neutron stars, direct experimental evidence only emerged recently using ultracold atoms. Existing methods rely on complex cavity setups or highly magnetic atoms, which impose rigid symmetries and limit the size of the supersolid. The researchers propose a simpler single-mirror system that gives the atoms complete freedom to self-organise in two dimensions, potentially creating larger and more exotic structures. If successful, the work will produce the first quasiperiodic supersolids—crystals with rotational symmetries (five, eight, ten, or twelve-fold) that cannot exist in ordinary solids. It will also realise a long-standing toy model in statistical physics and link to the controversial concept of time crystals. This is purely fundamental science. There is no immediate practical application, but past work on ultracold atoms has led to atomic clocks, quantum sensors, and the foundations of quantum computing. A deeper understanding of supersolids could one day inform new materials or precision measurement techniques.
View original technical description
Bose-Einstein condensates are macroscopic quantum states of atoms characterized by a single wavefunction. They exhibit superfluid properties, allowing atoms to flow without friction. In contrast, crystals consist of a periodic arrangement of atoms that do no move within the structure. Supersolids intriguingly combine these properties, as they possess both periodic order and superfluidity. Supersolid behaviour was initially proposed in the context of low-temperature phases of helium and they are also expected to exist in the crust of neutron stars. However, evidence for supersolidity remained elusive in condensed-matter physics in spite of significant research effort and direct experimental evidence of supersolid structures was only recently obtained in experiments using ultracold atoms. These realizations of supersolids build on the idea of “quantum simulation”, i.e. they utilize a highly controlled system of ultracold atoms to mimic the dynamics of a complex condensed matter or astrophysical system. In this project, we are proposing an alternative quantum simulation approach to supersolids in which detuned laser light mediates interactions between ultracold caesium atoms via a single feedback mirror. Compared to transversely pumped cavities, one of the schemes in which previous realizations of light-mediated supersolids were reported, our proposed experimental apparatus is considerably simpler and has only one distinguished axis, the pump axis. This allows for the complete freedom of self-organization and symmetry breaking in the plane orthogonal to the pump, whereas in transversely pumped cavities symmetries and length scales of the emerging supersolids are prescribed by the geometry of intersecting cavity and pump axes. Another scheme where supersolids have been recently obtained are degenerate quantum gases with very high magnetic moments. Compared to these systems, we expect to be able to create larger supersolids. Additionally, the flexibility to control light-mediated interactions in the single-mirror system enables us to demonstrate structures beyond stripes, hexagons or honeycombs observed in dipolar systems. After the initial observation of supersolids in 1D (stripes) and 2D (hexagons) using this approach, we will explore the spontaneous emergence of supersolids with a quasiperiodic symmetry. These supersolids are expected to exhibit a rotational symmetry (e.g., five, eight, ten or twelve-fold) not compatible with translational symmetry, and we will explore their unique properties. Although quasiperiodic crystals are known in condensed matter physics and received recent interest in the ultracold atoms community, quasiperiodic supersolids are a novel material. Additionally, we will study the formation of quantum droplets that are self-confined, localized patches of matter-like drops of liquids, and their transition to droplet arrays. Our preliminary numerical simulations indicate that, unless the final ground state is carefully seeded, the structures show a high-amplitude oscillation which is very long-lived. We also established a connection to the Hamiltonian Mean Field (HMF) model, a fundamental toy model in statistical physics for long-range coupled systems, which would get a first experimental realization. As the mapping of the single-mirror feedback dynamics to the HMF is only rigorously valid for a single period of the structure, we can study the persistence of the dynamics versus system size, i.e. the number of unit cells in the spatial structure. This research will enhance the knowledge on persistent dynamics in the statistical physics of long-range coupled systems. This also links to the hotly debated time crystals, i.e., time-dependent ground states that are forbidden by a no-go theorem in many quantum systems, but not in long-range coupled systems.
Plain English summaries and category classifications on this site are generated by AI and may not perfectly reflect the original research.
Is something wrong? Let us know