Phase diagram of the two-dimensional negative-<i>U</i>Hubbard model

Scalettar, Richard; Loh, Eugene; Gubernatis, J. E.; Moreo, Adriana; White, Steven R.; Scalapino, D. J.; Sugar, R.; Dagotto, Elbio

doi:10.1103/physrevlett.62.1407

Cited by 287 publications

(248 citation statements)

References 15 publications

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“…Precisely at the Heisenberg antiferromagnet (AF), the effect of a field H z is known: It breaks the full rotational symmetry and selects ordering in the XY plane since the spins can more easily take advantage of the field energy. This argument has been used to suggest why doping favors the superconducting over the CDW state in the negative-U Hubbard model [7] where an analogous "supersolid" symmetry exists at half-filling.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian

et al. 1995

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The Bose-Hubbard model exhibits a rich phase diagram consisting both of insulating regimes where diagonal long range (solid) order dominates as well as conducting regimes where off diagonal long range order (superfluidity) is present. In this paper we describe the results of Quantum Monte Carlo calculations of the phase diagram, both for the hard and soft core cases, with a particular focus on the possibility of simultaneous superfluid and solid order.We also discuss the appearance of phase separation in the model. The simulations are compared with analytic calculations of the phase diagram and spin wave dispersion.

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Section: Introductionmentioning

confidence: 99%

Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian

et al. 1995

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“…For this reason, more elaborate techniques such as diagrammatic resummations or Quantum MC approximations have been used to address the many puzzling questions of strongly coupled superconductors. While for the case of superconductivity with s-wave symmetry (sSC) this effort can be carried out with the attractive Hubbard model [4], the direct study of phase fluctuations for d-wave superconductors (dSC) remains a challenge. To our knowledge, in the vast literature on cuprates there is no available model where the physics of a strongly coupled dSC with short coherence lengths and large phase fluctuations can be studied accurately, with nearly exact solutions [5].…”

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Phase Fluctuations in Strongly Coupledd-Wave Superconductors

et al. 2005

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Tennessee 37996 and Condensed Matter Sciences Division, Oak Ridge National Lab, TN 37381, USAWe present a numerically exact solution for the BCS Hamiltonian at any temperature, including the degrees of freedom associated with classical phase, as well as amplitude, fluctuations via a Monte Carlo (MC) integration. This allows for an investigation over the whole range of couplings: from weak attraction, as in the well-known BCS limit, to the mainly unexplored strong-coupling regime of pronounced phase fluctuations. In the latter, for the first time two characteristic temperatures T ⋆ and Tc, associated with short-and long-range ordering, respectively, can easily be identified in a mean-field-motivated Hamiltonian. T ⋆ at the same time corresponds to the opening of a gap in the excitation spectrum. Besides introducing a novel procedure to study strongly coupled d-wave superconductors, our results indicate that classical phase fluctuations are not sufficient to explain the pseudo-gap features of high-temperature superconductors (HTS). One of the most fascinating aspects of the HTS is that a theoretical description in traditional BCS terms -using Cooper pairs -is feasible, yet in many other aspects these materials seem to deviate considerably from the standard BCS behavior. Most notorious in this respect is the curious "pseudogap" (PG) phase in the underdoped regime. The PG has attracted enormous interest in recent years and its effects have been studied using a wide variety of techniques [1], [2]. It is identified as a dip in the density of states N (ω) below a temperature T ⋆ , which is higher than the superconducting (SC) critical temperature T c , and its presence is sometimes attributed to a strong coupling between the charge carriers and accompanying phase fluctuations [3]. If this is the case, then conventional mean-field (MF) methods should not work in describing the cuprates, since they cannot distinguish between T ⋆ and T c . For this reason, more elaborate techniques such as diagrammatic resummations or Quantum MC approximations have been used to address the many puzzling questions of strongly coupled superconductors. While for the case of superconductivity with s-wave symmetry (sSC) this effort can be carried out with the attractive Hubbard model [4], the direct study of phase fluctuations for d-wave superconductors (dSC) remains a challenge. To our knowledge, in the vast literature on cuprates there is no available model where the physics of a strongly coupled dSC with short coherence lengths and large phase fluctuations can be studied accurately, with nearly exact solutions [5]. From the theory perspective, this is a conspicuous bottleneck in the HTS arena.Here, we introduce a novel and simple approach to alleviate this problem. The proposed method allows for an unbiased treatment of phenomena associated with classical (thermal) phase fluctuations and non-coherent pairbinding. It represents an extension of the original solution of the pairing Hamiltonian and has been made possible mostly due to the advan...

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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: 69%

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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Phase diagram of the two-dimensional negative-UHubbard model

Cited by 287 publications

References 15 publications

Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian

Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian

Phase Fluctuations in Strongly Coupledd-Wave Superconductors

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

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