Enhancement of Pairing Correlation by<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>t</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math>in the Two-Dimensional Extended<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mo>−</mml:mo><mml:mi>J</mml:mi></mml:math>Model

Mechanisms of Mott transitions and d x 2 Ày 2 -wave superconductivity (SC) are studied in the half-filledband Hubbard model on square lattices with a diagonal hopping term (t 0 ), using an optimization (or correlated) variational Monte Carlo method. In the trial wave functions, a doublon-holon binding effect is introduced in addition to the onsite Gutzwiller projection. We mainly treat a d-wave singlet state and a projected Fermi sea. In both wave functions, first-order Mott transitions without direct relevance to magnetic orders occur at U ¼ U c , which is approximately the bandwidth, for arbitrary t 0 =t. These transitions originate in the binding or unbinding of a doublon to a holon. d-wave SC appears in a narrow range immediately below U c . The robust d-wave superconducting correlation is necessarily accompanied by enhanced antiferromagnetic correlation; the strength of SC decreases, as t 0 =t increases.

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“…For the strongcorrelation regime (U > U max ), P d ðrÞ becomes almost constant for jrj ! 3, 62,63) as shown in Fig. 23.…”

Section: Pair Correlation Functionmentioning

confidence: 98%

Mott Transitions and d-Wave Superconductivity in Half-Filled-Band Hubbard Model on Square Lattice with Geometric Frustration

2006

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“…For the strong coupling model, i. e., t-J model with t' and t"=-t'/2, the SC correlation was reported to increase with decreasing t' from zero to about -0.30 and then to decrease by use of a VMC calculation [13]. The difference of the transient t' value may from the smaller lattice size (L=12) as well as the difference of the model.…”

Section: Bulk-limit Sc E Cond As a Function Of T'mentioning

confidence: 99%

t′- and t″-dependence of the bulk-limit superconducting condensation energy of the 2D Hubbard model

Yamaji

Yanagisawa

Miyazaki

et al. 2008

Physica C: Superconductivity

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The 2D Hubbard model having the 2nd-and 3rd-neighbor transfer energies t' and t" is investigated by use of the variational Monte Carlo method. At the nearly optimal doping with on-site Coulomb energy U=6 (energy unit is t) the condensation energy E cond for the d-wave superconductivity (SC) is computed for lattices of sizes from 10¥10 to 28¥28 with the aim to get its bulk-limit value. t" is fixed at -t'/2. Outside and in the neighborhood of the SDW region of -0.16£t'£-0.08 the SC E cond dominates over the SDW E cond . At t'=-0.05 and -0.10 we obtained a definitely finite bulk-limit SC E cond of the order of the experimental value for YBCO. At t'=0 E cond nearly vanishes. For t'£-0.18, the SC E cond strongly oscillates as a function of the lattice size, when periodic boundary conditions (b.c.'s) are imposed to both axes. In the case of periodic and anti periodic b.c.'s, a finite bulk-limit value is obtained at t'=-0.22. E cond tends to vanish with further decrease of t'. With our results the SC of LSCO is understandable with t'~-0.10. 2The t' values of Hg1201, Tl2201 and Na-CCOC seem close to -0.20 so that they locate in the boundary zone of SC indicated in the present work. Slightly larger U improves the situation by increasing E cond .

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“…16,17 The method has been extended more recently to study the coexistence of (and competition between) various phases like antiferromagnetism, flux states, and superconductivity in the t − J model 23,24,25,26 . Motivated by the phenomenology of the high temperature superconductors, other improvements such as the inclusion of longer range hopping terms 27 , increase of the number of variational parameters, and introduction of long range correlations through Jastrow factors 28 have also been proposed. Here, we extend previous works by allowing a symmetry breaking between the x− and the y−direction in the variational wavefunction |Ψ .…”

Section: Model and Vmc Schemementioning

confidence: 99%

Spontaneous breaking of the Fermi-surface symmetry in thet−Jmodel: A numerical study

2006

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We present a variational Monte Carlo (VMC) study of spontaneous Fermi surface symmetry breaking in the t − J model. We find that the variational energy of a Gutzwiller projected Fermi sea is lowered by allowing for a finite asymmetry between the x-and the y-directions. However, the best variational state remains a pure superconducting state with d-wave symmetry, as long as the underlying lattice is isotropic. Our VMC results are in good overall agreement with slave boson mean field theory (SBMFT) and renormalized mean field theory (RMFT), although apparent discrepancies do show up in the half-filled limit, revealing some limitations of mean field theories. VMC and complementary RMFT calculations also confirm the SBMFT predictions that many-body interactions can enhance any anisotropy in the underlying crystal lattice. Thus, our results may be of consequence for the description of strongly correlated superconductors with an anisotropic lattice structure.

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Enhancement of Pairing Correlation byt′in the Two-Dimensional Extendedt−JModel

Cited by 107 publications

References 22 publications

Mott Transitions and d-Wave Superconductivity in Half-Filled-Band Hubbard Model on Square Lattice with Geometric Frustration

Mott Transitions and d-Wave Superconductivity in Half-Filled-Band Hubbard Model on Square Lattice with Geometric Frustration

t′- and t″-dependence of the bulk-limit superconducting condensation energy of the 2D Hubbard model

Spontaneous breaking of the Fermi-surface symmetry in thet−Jmodel: A numerical study

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