Emergence of Crystalline Few-body Correlations in Mass-imbalanced Fermi Polarons

TL;DR

This paper investigates how crystalline few-body correlations emerge in mass-imbalanced Fermi polarons in two dimensions, revealing a smooth crossover to trimer and tetramer regimes with distinct momentum-space structures.

Contribution

It introduces a unified variational approach to identify dominant few-body correlations and describes the smooth crossover phenomena in mass-imbalanced Fermi polarons.

Findings

Crystalline trimer and tetramer correlations emerge in the polaron regime.

A smooth crossover from polaronic to few-body bound states occurs with increasing attraction.

Momentum-space crystallization features stable diagonal or triangular structures.

Abstract

Polarons can serve as an ideal platform to identify few-body correlations in tackling complex many-body problems. In this work, we reveal various crystalline few-body correlations smoothly emergent from the mass-imbalanced Fermi polarons in two dimensions. A unified variational approach up to three particle-hole excitations allows us to extract the dominant dimer, trimer or tetramer correlation in a single framework. When the fermion-impurity mass ratio is beyond certain critical value, the Fermi polaron is found to undergo a smooth crossover, instead of a sharp transition, from the polaronic to trimer and tetramer regimes as increasing the fermion-impurity attraction. The emergent trimer and tetramer correlations result in the momentum-space crystallization of particle-hole excitations featuring a stable diagonal or triangular structure, as can be directly probed through the density-density correlation of majority fermions. Our results shed light on the intriguing quantum phases in the mass-imbalanced Fermi-Fermi mixtures beyond the pairing superfluid paradigm.