BCS-BEC crossover of ultracold ions driven by density-dependent short-range interactions in a quantum plasma

We study theoretically a Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover of two-species ions in a three-dimensional quantum plasma at zero temperature. Central to this crossover is an effective short-ranged, attractive interaction potential between the ions shielded by the surrounding degenerate electrons. The interaction range and magnitude can be tuned nonmonotonically by varying the carrier density of the quantum plasma. Low-energy collisions between two ions are characterized by the s-wave scattering length when the interaction range and the inter-ion spacing are comparable. We show that the s-wave scattering length can be changed from -infinity to infinity, leading to a BCS-BEC crossover driven purely by the plasma density. Through numerical and analytical calculations, we find that the quantum acoustic waves in the plasma exhibit distinct dispersion relations in the different regimes, providing a route to probe the crossover. Our paper shows that the quantum plasma may offer a different platform to quantum simulate the BEC-BCS crossover and exotic phases with added tunability that might be difficult to achieve in conventional solid-state systems and ultracold atom gases.

Automated summary

Theoretical study of a BCS to BEC crossover in a three-dimensional quantum plasma at zero temperature shows that the interaction range and magnitude between two-species ions can be nonmonotonically tuned by varying the carrier density of the plasma. Low-energy collisions between ions are characterized by the s-wave scattering length, which can be changed from -infinity to infinity driven purely by plasma density. Quantum acoustic waves in the plasma exhibit distinct dispersion relations in different regimes, providing a route to probe the crossover.