Pairing state in multicomponent superconductors

Kuznetsova, Valentina; Barzykin, Victor

doi:10.1209/epl/i2005-10242-8

Cited by 14 publications

(13 citation statements)

References 34 publications

(71 reference statements)

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“…Based on symmetry arguments any linear combination of both d-wave components is possible below T c . However, both Ginzburg-Landau and BCStype mean-field approaches favor superconducting phases that break the time-reversal symmetry for singlet multicomponent superconductors [43,44], such as the d + id singlet pairing state predicted in graphene [21,25] and the cobaltates [20,22]. Therefore, our findings support the possibility of a chiral d + id superconducting phase in the hole-doped triangular Hubbard model.…”

supporting

confidence: 68%

Unconventional superconductivity on the triangular lattice Hubbard model

Chen

Meng

et al. 2013

Phys. Rev. B

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Using large-scale dynamical cluster quantum Monte Carlo simulations, we explore the unconventional superconductivity in the hole-doped Hubbard model on the triangular lattice. Due to the interplay of electronic correlations, geometric frustration, and Fermi surface topology, we find a doubly degenerate singlet pairing state at an interaction strength close to the bare bandwidth. Such an unconventional superconducting state is mediated by antiferromagnetic spin fluctuations along the $\Gamma$-$K$ direction, where the Fermi surface is nested. An exact decomposition of the irreducible particle-particle vertex further confirms the dominant component of the effective pairing interaction comes from the spin channel. Our findings provide support for chiral $d +i d$ superconductivity in water-intercalated sodium cobaltates Na$_{x}$CoO$_{2} \cdot y$H$_{2}$O, as well as insight into the superconducting phases of the organic compounds $\kappa$-(ET)$_{2}$X and Pd(dmit)$_{2}$.Comment: 5 pages, 4 figure

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supporting

confidence: 68%

Unconventional superconductivity on the triangular lattice Hubbard model

Chen

Meng

et al. 2013

Phys. Rev. B

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“…That is different from the case of Sr 2 RuO 4 where the two components of the order parameter necessary to explain the data belong to a single two-dimensional representation E 2u of the point group D 4h [22]. Although the present lattice is nearly triangular, the two components of the order parameter that we found do not coalesce into a single two-dimensional representation of the D 6h group [30]. Nevertheless, the mixed A 1g + B 1g representation for the orthorhombic crystal does coalesce into the one-dimensional A g representation of its monoclinic cousin, leading to a single T c in that case.…”

contrasting

confidence: 98%

Mixed pairing symmetry inκ−(BEDT-TTF)2Xorganic superconductors from ultrasonic velocity measurements

et al. 2009

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Discontinuities in elastic constants are detected at the superconducting transition of layered organic conductors κ-(BEDT-TTF)2X by longitudinal and transverse ultrasonic velocity measurements. Symmetry arguments show that discontinuities in shear elastic constants can be explained in the orthorhombic compound only if the superconducting order parameter has a mixed character that can be of two types, either A1g + B1g or B2g + B3g in the classification of irreducible representations of the orthorhombic point group D 2h . Consistency with other measurements suggests that the A1g + B1g (dxy + d z(x+y) ) possibility is realized. Such clear symmetry-imposed signatures of mixed order parameters have not been observed in other superconducting compounds.PACS numbers: 74.70. Kn,74.25.Ld,74.20.Pp Unconventional, non s-wave, superconductors in solids seem ubiquitously associated with strong electronic correlations. This is the case in a wide variety of compounds that include heavy fermions, ruthenates, cuprates as well as quasi-two-dimensional half-filled organic charge transfer salts κ-(ET) 2 X (ET = BEDT-TTF) [1]. In most cases gaps with nodes are observed, but the exact symmetry of the unconventional superconducting order parameter is uncontroversial only in the cuprates.In this letter, we focus on the layered organics that exhibit antiferromagnetism and Mott insulating behavior, as the cuprates, and establish the two-component nature of the singlet order parameter in the orthorhombic compound κ-(ET) 2 Cu[N(CN) 2 ]Br. Previous studies suggest d-wave pairing with nodes, although s-wave symmetry is sometimes seen. Measurements sensitive to the k-space dispersion, such as scanning tunneling spectroscopy [2] and thermal conductivity [3], favor d xy symmetry, namely nodes along the nearest neighbor bonds (or equivalenty, between the orthorhombic axes). Moreover, theoretical calculations based either on spin-fluctuation mediated superconductivity [4,5,6,7] or on quantum cluster methods [8,9] and variational approaches [10] for the Hubbard model, support the anisotropic d-wave picture with a prevailing d x 2 −y 2 symmetry. Nevertheless, none of these calculations has considered interlayer hopping, which, as we will show, is necessary to explain the experimental data that we present.The ultrasonic probe is extremely sensitive to gap anisotropies as the attenuation and velocity depend on both the direction of wave propagation and the direction of polarization. Attenuation experiments on UPt 3 [11, 12] and of Sr 2 RuO 4 [13] perfectly illustrate how the unconventional gap structure can be unraveled by such a versatile technique. In organic charge transfer salts how- * Present address: Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 ever, attenuation experiments are hampered by the small size and the shape of single crystals. Nevertheless, one experiment was successful for the κ-(ET) 2 Cu[N(CN) 2 ]Br compound [14], but the interpretation of the results was complicated by a phas...

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“…This means both solutions necessarily have the same transition temperature T c [14,15]. Below T c higher order terms become important in the energy functional and the complex combination d x 2 −y 2 ± id xy (d ± id ) is very generally favored [14][15][16][17][18][19][20][21][22][23]. The d ± id state is a chiral, time-reversal symmetry breaking state with the chirality set by the sign between the two different d-wave components [24][25][26] and where the nontrivial topology [27] guarantees the existence of two co-propagating, i.e., chiral, edge states [26,28].…”

Section: Introductionmentioning

confidence: 99%

Chirald-wave superconductivity on the honeycomb lattice close to the Mott state

2014

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We study superconductivity on the honeycomb lattice close to the Mott state at half filling. Due to the sixfold lattice symmetry and disjoint Fermi surfaces at opposite momenta, we show that several different fully gapped superconducting states naturally exist on the honeycomb lattice, of which the chiral d + id -wave state has previously been shown to appear when superconductivity appears close to the Mott state. Using renormalized mean-field theory to study the t-J model and quantum Monte Carlo calculations of the Hubbard-U model we show that the d + id -wave state is the favored superconducting state for a wide range of on-site repulsion U , from the intermediate to the strong coupling regime. We also investigate the possibility of a mixed chirality d-wave state, where the overall chirality cancels. We find that a state with d + id -wave symmetry in one valley but d − id -wave symmetry in the other valley is not possible in the t-J model without reducing the translational symmetry, due to the zero-momentum and spin-singlet nature of the superconducting order parameter. Moreover, any extended unit cells result either in disjoint Dirac points, which cannot harbor this mixed chirality state, or the two valleys are degenerate at the zone center, where valley hybridization prevents different superconducting condensates. We also investigate extended unit cells where the overall chirality cancels in real space. For supercells containing up to eight sites, including the Kekulé distortion, we find no energetically favorable d-wave solution with an overall zero chirality within the restriction of the t-J model.

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Pairing state in multicomponent superconductors

Cited by 14 publications

References 34 publications

Unconventional superconductivity on the triangular lattice Hubbard model

Unconventional superconductivity on the triangular lattice Hubbard model

Mixed pairing symmetry inκ−(BEDT-TTF)2Xorganic superconductors from ultrasonic velocity measurements

Chirald-wave superconductivity on the honeycomb lattice close to the Mott state

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