BCS-BEC crossover at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn></mml:mrow></mml:math>: A dynamical mean-field theory approach

Garg, Arti; Krishnamurthy, H. R.; Randeria, Mohit

doi:10.1103/physrevb.72.024517

Cited by 78 publications

(103 citation statements)

References 39 publications

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“…At half-filling the superfluid state and the ADW state are degenerate, while in the filling deviated from the half-filling the superfluid state is the most stable [23,24,25]. In the present system, the ADW state persists up to a certain value of D for given U .…”

Section: Numerical Resultsmentioning

confidence: 67%

“…To investigate these states, we calculate the superfluid order parameter Φ = c iα↓ c iα↑ , the quasiparticle weight Z, and the ADW order parameter M ADW = (1/4)(n B − n A ), where n B(A) = α,σ n B(A)ασ with n B(A)ασ = c † B(A)iασ c B(A)ασ being the number operator of the B(A) sublattice per site. Z represents the coherent spectral weight of the Bogoliubov quasiparticle [23]. Because of particle-hole symmetry, Φ is independent of α.…”

Section: Numerical Resultsmentioning

confidence: 99%

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Density-wave and antiferromagnetic states of fermionic atoms in optical lattices

Higashiyama

Suga

2009

Phys. Rev. A

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We study the two-band effects on ultracold fermionic atoms in optical lattices by means of dynamical mean-field theory. We find that at half-filling the atomic-density-wave (ADW) state emerges owing to the two-band effects in the attractive interaction region, while the antiferromagnetic state appears in the repulsive interaction region. As the orbital splitting is increased, the quantum phase transitions from the ADW state to the superfluid state and from the antiferromagnetic state to the metallic state occur in respective regions. Systematically changing the orbital splitting and the interaction, we obtain the phase diagram at half-filling. The results are discussed using the effective boson model derived for the strong attractive interaction.

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Section: Numerical Resultsmentioning

confidence: 67%

Section: Numerical Resultsmentioning

confidence: 99%

Density-wave and antiferromagnetic states of fermionic atoms in optical lattices

Higashiyama

Suga

2009

Phys. Rev. A

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“…We emphasize that the Mott transition is caused by the multiband effects. In fact, the transition from the superfluid to the Mott insulator has not been obtained in the single-band attractive Hubbard model [18,19,20]. In Fig.…”

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confidence: 97%

“…Z represents the coherent spectral weight of the Bogoliubov quasiparticle [18], which enables us to examine the Mott transition accurately. For half filling, Φ becomes independent of i and α in the DMFT procedure.…”

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confidence: 99%

Multiband-driven superfluid-insulator transition of fermionic atoms in optical lattices: A dynamical mean-field-theory study

Higashiyama

Suga

2008

Phys. Rev. A

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The superfluid-insulator transitions of the fermionic atoms in optical lattices are investigated by the two-site dynamical mean-field theory. It is shown that the Mott transition occurs as a result of the multiband effects. The quasiparticle weight in the superfluid state decreases significantly, as the system approaches the Mott transition point. By changing the interaction and the orbital splitting, we obtain the phase diagram at half filling. The numerical results are discussed in comparison with the effective boson model. PACS numbers: 03.75.Lm, 05.30.Fk, 73.43.Nq Since the superfluid of trapped atomic Fermi gases 40 K and 6 Li was observed [1,2,3,4,5,6], intense theoretical and experimental studies have been done for ultracold atomic Fermi gases. In these experiments, magnetic-field Feshbach resonances provide the means for controlling both the strength of the interaction between fermionic atoms and its sign [7]. These tunable interactions enable us to observe the crossover between the BCS superfluid for the weak attractive interaction and the Bose-Einstein condensate (BEC) of bound pairs for the strong attractive interaction. Furthermore, by loading atoms into optical lattices, diverse interaction configurations can be introduced. The combination of these two experimental techniques plays an important role in the study of ultracold fermionic atoms and offers the experimental description of various intriguing quantum many-body phenomena.Recent experiments revealed fascinating aspects of fermionic atoms in three dimensional optical lattices [8,9]. In the ETH experiment, a band insulator in the lowest band was produced, i.e. two atoms in different hyperfine states occupy the lowest state per lattice site [8]. Controlling the interaction, they further observed the partially populated higher bands. In the MIT experiment, a superfluidity of fermionic atom pairs in an optical lattice was observed [9]. By increasing the depth of the lattice potential near the Feshbach resonance, a superfluid-insulator transition was observed. They argued that the insulating state was the Mott insulator. In these experiments, it was argued that the usual singleband Hubbard model was no longer applicable, because the strength of the on-site interaction exceeded the gap between the lowest and the next-lowest bands. For detailed investigations of the experiments, accordingly, the effects of the higher bands have to be taken into account.Stimulated by these experiments, several theoretical studies on the superfluid-insulator transition were carried out [10,11,12]. However, both the correlation effects and the multiband effects have not yet been investigated well enough to discuss the transition from superfluid to Mott insulator. Precise studies including both effects are thus required.In this paper, we investigate the superfluid-insulator transition of interacting fermionic atoms in optical lattices, taking into account the multiband effects. For this purpose, we make use of a dynamical mean-field theory (DMFT) [13]. This method ena...

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“…[35][36][37][38][39][40][41] It is known that the DW and SF states are degenerate on a bipartite lattice in two and higher dimensions at half filling. Each order parameter can be defined by…”

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confidence: 99%

Low-Temperature Properties of the Fermionic Mixtures with Mass Imbalance in Optical Lattice

Takemori

Koga

2012

J. Phys. Soc. Jpn.

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We study the attractive Hubbard model with mass imbalance to clarify the low-temperature properties of fermionic mixtures in an optical lattice. By combining dynamical mean-field theory with continuous-time quantum Monte Carlo simulation, we discuss the competition between the superfluid and density wave states at half filling. By calculating the energy and order parameter for each state, we clarify that the coexisting (supersolid) state, where the density wave and superfluid states are degenerate, is realized in the system. We then determine the phase diagram at finite temperatures.KEYWORDS: superfluid, density wave, mass-imbalanced system, continuous-time Monte Carlo simulationThe superfluid state in ultracold fermionic systems has attracted considerable interest since the successful realization of the Bose-Einstein condensation in 6 Li 2 molecules. 1,2) Owing to the high controllability of the system, remarkable phenomena have been observed such as the BCS-BEC crossover 3,4) and the superfluid state in a spin-imbalanced system, 5,6) where Cooper pairs are composed of ions with distinct hyperfine states. Recently, fermionic mixtures with distinct ions, e.g., 6 Li and 40 K, have experimentally been realized, 7,8) which stimulates further theoretical investigations on superfluid states in a mass-imbalanced system. [9][10][11][12][13][14][15][16][17] One of the interesting questions in such a massimbalanced system is how the superfluid state is realized when the lattice potential is loaded, so called an optical lattice. 18) In the lattice system, 19) the density wave (DW) state is naively expected, in addition to the SF state, since less mobile fermions tend to crystallize in the lattice, particularly, at half filling. It is desired to systematically discuss how the SF state competes or coexists with the DW state in an optical lattice system. This topic is closely related to an important issue in condensed matter physics, so called the supersolid state, [20][21][22][23][24] since the DW state can be regarded as a type of solid state. Therefore, an optical lattice system with mass imbalance should provide an ideal stage for studies of supersolid state in fermionic systems.Motivated by this, we study the low-temperature properties of a fermionic mixture in an optical lattice, combining dynamical mean-field theory (DMFT) 25) with continuoustime quantum Monte Carlo (CTQMC) simulation. 26,27) By calculating the order parameters for the DW and SF states, we determine the phase diagram at finite temperatures and clarify how the coexisting state is stabilized against the mass imbalance.In this paper, we consider the following attractive Hubbard model with different masses 19) aswhere hi; ji denotes the nearest neighbor site, c y i ðc i Þ is the creation (annihilation) operator of a fermion at the ith site with spin ð¼ "; #Þ and n i ¼ c y i c i . U ð> 0Þ is the attractive interaction and t is the hopping amplitude for the fermion with spin , where the effect of the mass imbalance is taken into account.We examine the low-t...

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BCS-BEC crossover atT=0: A dynamical mean-field theory approach

Cited by 78 publications

References 39 publications

Density-wave and antiferromagnetic states of fermionic atoms in optical lattices

Density-wave and antiferromagnetic states of fermionic atoms in optical lattices

Multiband-driven superfluid-insulator transition of fermionic atoms in optical lattices: A dynamical mean-field-theory study

Low-Temperature Properties of the Fermionic Mixtures with Mass Imbalance in Optical Lattice

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