BEC-BCS crossover and universal relations in unitary Fermi gases

TL;DR

This paper uses quantum Monte Carlo methods to precisely calculate the contact parameter in unitary Fermi gases, demonstrating its universal role in various observables and deriving related theoretical expressions.

Contribution

It provides highly accurate quantum Monte Carlo calculations of the contact parameter and derives Tan's relations from the short-range behavior of the wave function.

Findings

Precise value of the contact parameter at T=0

Universal applicability of the contact to multiple observables

Identification of momentum and energy regions dominated by short-range behavior

Abstract

The contact parameter in unitary Fermi Gases governs the short-distance, high-momentum, and high-energy properties of the system. We perform accurate quantum Monte Carlo calculations with highly optimized trial functions to precisely determine this parameter at T=0, demonstrate its universal application to a variety of observables, and determine the regions of momentum and energy over which the leading short-range behavior is dominant. We derive Tan's expressions for the contact parameter using just the short-range behavior of the ground-state many-body wave function, and use this behavior to calculate the two-body distribution function, one-body density matrix, and the momentum distribution of unitary Fermi gases; providing a precise value of the contact parameter that can be compared to experiments.