Nonequilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region

Taira, Kawamura,; Hanai, Ryo; Kagamihara, Daichi; Inotani, Daisuke; Ōhashi, Y.

doi:10.1103/physreva.101.013602

Cited by 14 publications

(23 citation statements)

References 77 publications

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“…that coincide with the positions of two edges imprinted on the Fermi momentum distribution n p,σ by the two reservoirs [39] (see Fig. 1).…”

Section: Ivbsupporting

confidence: 63%

“…When one takes the spatial averages over the randomly distributing tunneling positions R α i and r α i in Eq. ( 22), the resulting self-energy Σenv (p, p , t 1 , t 2 ) av recovers its the translational invariance as Σenv (p, p , t 1 , t 2 ) av = Σenv (p, t 1 , t 2 )δ p,p [39,[43][44][45], where…”

Section: (B) Evaluation Of This Diagram Givesmentioning

confidence: 86%

“…In Eq. ( 4), the factor exp(iτ 3 µ α t) describes the situation that the energy band in the α-reservoir is filled up to µ α at T env = 0, when the energy is measured from the bottom (ε p=0 = 0) of the energy band in the main system [39,46,47]. By imposing the chemical-potential bias µ L = µ + δµ and µ R = µ − δµ (δµ > 0) between the two reservoirs, we realize the non-equilibrium steady state in the main system.…”

Section: A Model Driven-dissipative Non-equilibrium Fermi Gasmentioning

confidence: 99%

“…are vertex matrices [39], where σ i=1,2,3 are the Pauli matrices acting on the Keldysh space. Tr N and Tr K stand for taking the trace over the Nambu and the Keldysh space, respectively.…”

Section: B Non-equilibrium Nambu-keldysh Green's Functionmentioning

confidence: 99%

“…This FF-like state is stabilized by the two-edge structure of the Fermi momentum distribution n p,σ (see Fig. 1), which is produced by the pumping and decay of atoms by the two reservoirs [39]. The two edges at p F1 = √ 2mµ R and p F2 = √ 2mµ L then work like two Fermi surfaces with different sizes, and Cooper pairs (A) and (B) in Fig.…”

Section: Introductionmentioning

confidence: 97%

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Fermi-surface-engineered unconventional superfluid states in a driven-dissipative non-equilibrium Fermi gas

Kawamura,

Hanai,

Ohashi

2021

Preprint

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We develop a theory to describe the dynamics of a driven-dissipative many-body Fermi system, to pursue our proposal to realize exotic quantum states based on reservoir engineering. Our idea is to design the shape of a Fermi surface so as to have multiple Fermi edges, by properly attaching multiple reservoirs with different chemical potentials to a fermionic system. These emerged edges give rise to additional scattering channels that can destabilize the system into unconventional states, which is exemplified in this work by considering a driven-dissipative attractively interacting Fermi gas. By formulating a quantum kinetic equation using the Nambu-Keldysh Green's function technique, we determine the nonequilibrium steady state of this system and assess its stability. We find that, besides the BCS-type isotropic pairing state, an anisotropic superfluid state being accompanied by Cooper pairs with non-zero center-of-mass momentum exists as a stable solution, even in the absence of a magnetic Zeeman field. Our result implies a great potential of realizing quantum matter beyond the equilibrium paradigm, by engineering the shape and topology of Fermi surfaces in both electronic and atomic systems.

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“…that coincide with the positions of two edges imprinted on the Fermi momentum distribution n p,σ by the two reservoirs [39] (see Fig. 1).…”

Section: Ivbsupporting

confidence: 63%

Section: (B) Evaluation Of This Diagram Givesmentioning

confidence: 86%

Section: A Model Driven-dissipative Non-equilibrium Fermi Gasmentioning

confidence: 99%

“…are vertex matrices [39], where σ i=1,2,3 are the Pauli matrices acting on the Keldysh space. Tr N and Tr K stand for taking the trace over the Nambu and the Keldysh space, respectively.…”

Section: B Non-equilibrium Nambu-keldysh Green's Functionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

See 3 more Smart Citations

Fermi-surface-engineered unconventional superfluid states in a driven-dissipative non-equilibrium Fermi gas

Kawamura,

Hanai,

Ohashi

2021

Preprint

Self Cite

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Non-Hermitian BCS-BEC crossover of Dirac fermions

Kanazawa

2021

J. High Energ. Phys.

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We investigate chiral symmetry breaking in a model of Dirac fermions with a complexified coupling constant whose imaginary part represents dissipation. We introduce a chiral chemical potential and observe that for real coupling a relativistic BCS-BEC crossover is realized. We solve the model in the mean-field approximation and construct the phase diagram as a function of the complex coupling. It is found that the dynamical mass increases under dissipation, although the chiral symmetry gets restored if dissipation exceeds a threshold.

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Non-equilibrium BCS-BEC crossover and unconventional FFLO superfluid in a strongly interacting driven-dissipative Fermi gas

Kawamura,

Ohashi

2024

AAPPS Bull.

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We present a theoretical review of the recent progress in non-equilibrium BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover physics. As a paradigmatic example, we consider a strongly interacting driven-dissipative two-component Fermi gas where the non-equilibrium steady state is tuned by adjusting the chemical potential difference between two reservoirs that are coupled with the system. As a powerful theoretical tool to deal with this system, we employ the Schwinger-Keldysh Green’s function technique. We systematically evaluate the superfluid transition, as well as the single-particle properties, in the non-equilibrium BCS-BEC crossover region, by adjusting the chemical potential difference between the reservoirs and the strength of an s-wave pairing interaction associated with a Feshbach resonance. In the weak-coupling BCS side, the chemical potential difference is shown to imprint a two-step structure on the particle momentum distribution, leading to an anomalous enhancement of pseudogap, as well as the emergence of exotic Fulde-Ferrell-Larkin-Ovchinnikov-type superfluid instability. Since various non-equilibrium situations have recently been realized in ultracold Fermi gases, the theoretical understanding of non-equilibrium BCS-BEC crossover physics would become increasingly important in this research field.

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Nonequilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region

Cited by 14 publications

References 77 publications

Fermi-surface-engineered unconventional superfluid states in a driven-dissipative non-equilibrium Fermi gas

Fermi-surface-engineered unconventional superfluid states in a driven-dissipative non-equilibrium Fermi gas

Non-Hermitian BCS-BEC crossover of Dirac fermions

Non-equilibrium BCS-BEC crossover and unconventional FFLO superfluid in a strongly interacting driven-dissipative Fermi gas

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