Absence of Superconductivity in the Half-Filled Band Hubbard Model on the Anisotropic Triangular Lattice

Clay, R. Torsten; Li, H.; Mazumdar, S.

doi:10.1103/physrevlett.101.166403

Cited by 83 publications

(129 citation statements)

References 34 publications

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“…Spin structure factor AFM is best explained within the effective dimer model 1,[7][8][9][10][11][12][13][14][15]17 , where the charge densities on the molecules of the dimer are equal. Accordingly we define the total z-component of spin on dimer i as…”

Section: Resultsmentioning

confidence: 99%

“…As mentioned above, previous works have shown (i) suppression of pair-pair correlations within the effective ρ = 1 model [17][18][19][20] , and (ii) the possibility of a fluctuating CO within models focusing on the monomer molecules 33,34,[36][37][38] . We therefore construct pair creation operators that allow unequal charge densities on the monomer molecules that constitute a dimer in Fig.…”

Section: B Pair-pair Correlationsmentioning

confidence: 99%

“…A necessary condition for SC within any interacting electrons model however is that interactions must enhance superconducting pair-pair correlations relative to the noninteracting model. Precise numerical calculations within the 1 2 -filled band Hubbard model on triangular lattices have shown that pair-pair correlations decrease with Hubbard U for all anisotropy [17][18][19][20] , thus indicating the need for going beyond the effective 1/2-filled band model in our search for the the mechanism of SC in κ-(ET) 2 X.…”

Section: Introductionmentioning

confidence: 99%

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Coulomb enhancement of superconducting pair-pair correlations in a34-filled model forκ−(BEDT-TTF)2X

Silva¹,

Gomes²,

Mazumdar³

et al. 2016

Phys. Rev. B

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We present the results of precise correlated-electron calculations on the monomer lattices of the organic charge-transfer solids κ-(BEDT-TTF)2X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X = Cu[N(CN)2]Cl and Cu2(CN)3, which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities ρ per BEDT-TTF molecule, with ρ ranging from 1 to 2. We find that d-wave superconducting pair-pair correlations are enhanced by electron-electron interactions only for a narrow carrier concentration about ρ = 1.5, which is precisely the carrier concentration where superconductivity in the charge-transfer solids occurs. Our results indicate that the enhancement in pair-pair correlations is not related to antiferromagnetic order, but to a proximate hidden spin-singlet state that manifests itself as a charge-ordered state in other chargetransfer solids. Long-range superconducting order does not appear to be present in the purely electronic model, suggesting that electron-phonon interactions also must play a role in a complete theory of superconductivity.

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Section: Resultsmentioning

confidence: 99%

Section: B Pair-pair Correlationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coulomb enhancement of superconducting pair-pair correlations in a34-filled model forκ−(BEDT-TTF)2X

Silva¹,

Gomes²,

Mazumdar³

et al. 2016

Phys. Rev. B

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“…Recall that within existing mean field theories the AFM-to-SC transition is driven by spin fluctuations [13][14][15][16][17][18][19][20][21][22][23] , while the CO-to-SC transition is driven by charge fluctuations 65 . Even if we ignore that recent precise numerical calculations [25][26][27] have demonstrated the absence of SC within the proposed spin-fluctuation models in this context (thereby raising doubts also about mean-field theory of charge-fluctuation mediated superconductivity), different mechanisms of SC for structurally related materials with identical or nearidentical molecular components appear to be unrealistic. Within our proposed scenario, the charge-ordered or VBS systems that exhibit SC are PECs in the semiconducting state, while the AFM systems under pressure transform to PECs first and then to SC (although due to actual crystal structures the "width" of the PEC region could be narrow to vanishing within the latter).…”

Section: Consequence Of Stronger Frustration-paired Electron Liquid Amentioning

confidence: 99%

“…It has been claimed that this transition explains the SC in the CTS [13][14][15][16][17][18][19][20][21][22][23][24] . Recent numerical work by us and others, however, have determined that SC is absent within the ρ = 1 triangular lattice Hubbard model [25][26][27] and the earlier results are artifacts of mean-field approximations.…”

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confidence: 97%

Paired electron crystal: Order from frustration in the quarter-filled band

et al. 2011

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We present a study of the effects of simultaneous charge-and spin-frustration on the twodimensional strongly correlated quarter-filled band on an anisotropic triangular lattice. Our conclusions are based on exact diagonalization studies that include electron-electron interactions as well as adiabatic electron-phonon coupling terms treated self-consistently. The broken-symmetry states that dominate in the weakly frustrated region near the rectangular lattice limit are the well known antiferromagnetic state with in-phase lattice dimerization along one direction, and the Wigner crystal state with the checkerboard charge order. For moderate to strong frustration, however, the dominant phase is a novel spin-singlet paired-electron crystal (PEC), consisting of pairs of charge-rich sites separated by pairs of charge-poor sites. The PEC, with coexisting charge-order and spin-gap in two dimension, is the quarter-filled band equivalent of the valence bond solid (VBS) that can appear in the frustrated half-filled band within antiferromagnetic spin Hamiltonians. We discuss the phase diagram as a function of on-site and intersite Coulomb interactions as well as electronphonon coupling strength. We speculate that the spin-bonded pairs of the PEC can become mobile for even stronger frustration, giving rise to a paired-electron liquid. We discuss the implications of the PEC concept for understanding several classes of quarter-filled band materials that display unconventional superconductivity, focusing in particular on organic charge transfer solids. Our work points out the need to go beyond quantum spin liquid (QSL) concepts for highly frustrated organic charge-transfer solids such as κ-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2, which we believe show frustration-induced charge disproportionation at low temperatures. We discuss possible application to layered cobaltates and 1 4 -filled band spinels.

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Is there a common theme behind the correlated‐electron superconductivity in organic charge‐transfer solids, cobaltates, spinels, and fullerides?

Mazumdar

Clay

2012

Physica Status Solidi (b)

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We posit that there exist deep and fundamental relationships between the above seemingly very different materials. The carrier concentration-dependences of the electronic behavior in the conducting organic charge-transfer solids and layered cobaltates are very similar. These dependences can be explained within a single theoretical model, the extended Hubbard Hamiltonian with significant nearest neighbor Coulomb repulsion. Interestingly, superconductivity in the cobaltates seems to be restricted to bandfilling exactly or close to one-quarter, as in the organics. We show that dynamic JahnTeller effects and the resultant orbital ordering can lead to 1/4-filled band descriptions for both superconducting spinels and fullerides, which show evidence for both strong electronelectron and electron-phonon interactions. The orbital orderings in antiferromagnetic lattice-expanded bcc M 3 C 60 and the superconductor are different in our model. Strong correlations, quarter-filled band and lattice frustration are the common characteristics shared by these unusual superconductors.

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Absence of Superconductivity in the Half-Filled Band Hubbard Model on the Anisotropic Triangular Lattice

Cited by 83 publications

References 34 publications

Coulomb enhancement of superconducting pair-pair correlations in a34-filled model forκ−(BEDT-TTF)2X

Coulomb enhancement of superconducting pair-pair correlations in a34-filled model forκ−(BEDT-TTF)2X

Paired electron crystal: Order from frustration in the quarter-filled band

Is there a common theme behind the correlated‐electron superconductivity in organic charge‐transfer solids, cobaltates, spinels, and fullerides?

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