Nature of the polaron-molecule transition in Fermi polarons

Cheng, Peng; Liu, Ruijin; Zhang, Wei; Cui, Xiaoling

doi:10.1103/physreva.103.063312

Cited by 7 publications

(8 citation statements)

References 47 publications

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“…As pointed out in Ref. [30,31], M 2n+2 (0) expands a subset of the variational space of P 2n+3 (k F ), and thus the former is always energetically unfavorable as compared to the latter. However, in the strong coupling regime, M 2n+2 (0) can be a good approximation for P 2n+3 (k F ).…”

Section: Polaron-molecule Transition For η < ηTrmentioning

confidence: 89%

“…We emphasize that the generalized ansatz (2) systematically incorporates all the essential few-body correlations and thus can serve as a unified approach for the Fermi polaron problem. First, taking Q = 0, it describes the polaronic ground state for the weak coupling Fermi polarons, as studied previously with up to one [23,26,27,30,51,58,59,61] and two [22,31,52,60] p-h excitations. Secondly, taking a finite Q = k F , it well covers the molecule state with zero center-of-mass momentum as proposed in the strong coupling regime [22,23,26,27,51,52,61], where the impurity essentially binds with one fermion on the Fermi surface to form a dimer.…”

Section: Unified Variational Approachmentioning

confidence: 99%

“…Secondly, taking a finite Q = k F , it well covers the molecule state with zero center-of-mass momentum as proposed in the strong coupling regime [22,23,26,27,51,52,61], where the impurity essentially binds with one fermion on the Fermi surface to form a dimer. In this sense, it has been pointed out that the polaron-molecule transition can be recognized as the energy competition between different Q-sectors [30,31]. Finally, by including higher-order p-h excitations, all the few-body correlations can be systematically incorporated.…”

Section: Unified Variational Approachmentioning

confidence: 99%

“…It has been shown that the 3D and 2D Fermi polarons with equal mass can undergo a first-order transition from polaronic to molecular phase as increasing the impurity-fermion attraction [21][22][23][24][25][26][27][28][29], a consequence of enhanced two-body correlation therein. Using a unified treatment of polaron and molecule, such transition can be interpreted as the energy competition between different momentum states [30,31], where the molecule serves as a good approximation for the finitemomentum state in strong coupling limit (see also [32]) and possesses a huge hidden degeneracy. The inclusion of finite-momentum states [30,31,33] is crucial for explaining the smooth polaron-molecule evolution in realistic experiment with a finite impurity density and at finite temperature [5,8,12].…”

Section: Introductionmentioning

confidence: 99%

“…Using a unified treatment of polaron and molecule, such transition can be interpreted as the energy competition between different momentum states [30,31], where the molecule serves as a good approximation for the finitemomentum state in strong coupling limit (see also [32]) and possesses a huge hidden degeneracy. The inclusion of finite-momentum states [30,31,33] is crucial for explaining the smooth polaron-molecule evolution in realistic experiment with a finite impurity density and at finite temperature [5,8,12]. Besides, the polaron-molecule transition has profound implications to the property of highly-polarized spin-1/2 fermions, where a phase separation between normal and superfluid states can occur [34] as observed in cold atoms experiments [35,36].…”

Section: Introductionmentioning

confidence: 99%

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

Liu¹,

Cheng²,

Cui³

2022

Preprint

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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 polarontrimer-tetramer crossover as increasing the fermion-impurity attraction, in contrast to the polaronmolecule 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 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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Section: Polaron-molecule Transition For η < ηTrmentioning

confidence: 89%