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      Inhomogeneous superconductivity in the presence of time-reversal symmetry

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          Abstract

          We propose a new type of non-uniform condensate state in the presence of time-reversal symmetry. The underlying platform of this state is a corrugated honeycomb lattice which exhibits an inhomogeneous pseudo magnetic field. Using the self-consistent tight-binding Bogoliubov-de Gennes formalism, we show that an s-wave pairing of chiral carriers in the presence of an inhomogeneous pseudo magnetic field results in a spatially modulated order parameter with the half wavelength of the corrugation. The manner of modulation depends on the fundamental directions of the honeycomb lattice, the zigzag and armchair directions. The stability of this inhomogeneous superconductivity is also analyzed and possible experimental realization is discussed.

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          Chiral superconductivity from repulsive interactions in doped graphene

          We identify graphene as a system where chiral superconductivity can be realized. Chiral superconductivity involves a pairing gap that winds in phase around the Fermi surface, breaking time reversal symmetry. We consider a unique situation arising in graphene at a specific level of doping, where the density of states is singular, strongly enhancing the critical temperature T_c. At this doping level, the Fermi surface is nested, allowing superconductivity to emerge from repulsive electron-electron interactions. We show using a renormalization group method that superconductivity dominates over all competing orders for any choice of weak repulsive interactions. Superconductivity develops in a doubly degenerate, spin singlet channel, and a mean field calculation indicates that the superconductivity is of a chiral d+id type. We therefore predict that doped graphene can provide experimental realization of spin-singlet chiral superconductivity.
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            Strained graphene: tight-binding and density functional calculations

            We determine the band structure of graphene under strain using density functional calculations. The ab-initio band strucure is then used to extract the best fit to the tight-binding hopping parameters used in a recent microscopic model of strained graphene. It is found that the hopping parameters may increase or decrease upon increasing strain, depending on the orientation of the applied stress. The fitted values are compared with an available parametrization for the dependence of the orbital overlap on the distance separating the two carbon atoms. It is also found that strain does not induce a gap in graphene, at least for deformations up to 10%.
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              Author and article information

              Journal
              2016-05-27
              Article
              10.1209/0295-5075/110/47010
              1605.08541
              22ef426e-9b54-4788-9d97-c636a2730f90

              http://arxiv.org/licenses/nonexclusive-distrib/1.0/

              History
              Custom metadata
              EPL (Europhysics Letters), Volume 110, Number 4 (2015)
              6 pages, 6 figures
              cond-mat.supr-con cond-mat.mes-hall

              Condensed matter,Nanophysics
              Condensed matter, Nanophysics

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