2025/01/24 by Moksh Bhateja, N. Dupuis, Bhateja, Moksh +3
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Quantum Gases (cond-mat.quant-gas) #Quantum, superfluid, helium dynamics
paper · pdf · doi:10.48550/arxiv.2501.14884
openalex publication_date 2025/01/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
The two-body contact is a fundamental quantity of a dilute Bose gas that relates the thermodynamics to the short-distance two-body correlations. For a Bose gas in an optical lattice, near the superfluid--Mott-insulator transition, we show that a ``universal'' contact C\rm univ can be defined from the singular part P-P\rm MI of the pressure (P\rm MI is the pressure of the Mott insulator). Its expression C\rm univ=C\rm DBG(|n-n\rm MI|,a^*) coincides with that of a dilute Bose gas provided we consider the effective ``scattering length'' a^* of the quasi-particles at the quantum critical point (QCP) rather than the scattering length in vacuum, and the excess density |n-n\rm MI| of particles (or holes) with respect to the Mott insulator. Close to the transition, we find that the singular part n\rm sing\bf k = n\bf k - n\rm MI\bf k of the momentum distribution exhibits a high-momentum tail of the form Z\rm QP C\rm univ/|\bf k|4 over a broad region of the Brillouin zone, where Z\rm QP is the quasi-particle weight of the elementary excitations at the QCP. Our results demonstrate that the notion of contact extends to strongly correlated lattice bosons, and we argue that the contact C\rm univ can be measured in state-of-the-art experiments on Bose gases in optical lattices and magnetic insulators.