Kavli Affiliate: Cheng Peng
| First 5 Authors: Ruijin Liu, Cheng Peng, Xiaoling Cui, ,
| Summary:
Identifying few-body correlations is an efficient tool to solve complex
many-body problems. The polarons, interpolating between few- and many-body
systems, serve as an ideal platform to achieve the goal. In this work, we
reveal various crystalline few-body correlations emergent from a smooth
crossover of mass-imbalanced Fermi polarons in two dimension. Here a unified
variational approach up to three particle-hole excitations allows us to extract
the dominant $n$-body correlations for $n$ ranging from $2$ (dimer), $3$
(trimer) to $4$ (tetramer). It is found that when the fermion-impurity mass
ratio is beyond certain critical value, the Fermi polaron will undergo a smooth
polaron-trimer or polaron-trimer-tetramer crossover as increasing the
fermion-impurity attraction, in contrast to the polaron-molecule transition for
the equal mass case. During the crossover, the $3$- and $4$-body correlations
gradually emerge and become dominant, which can manifest themselves in the {it
momentum-space crystallization}, i.e., the particle-hole excitations of
majority fermions tend to distribute with equal interval near the Fermi surface
forming a stable diagonal or triangular structure. Such emergent
crystallization can be detected 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.
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