Odd-frequency pair density wave in the Kitaev-Kondo lattice model
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2021
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We investigate the properties of the Kitaev-Kondo lattice model defined on a bilayer honeycomb lattice by
means of the SO(3) Majorana representation for spin-1/2 moments. We first consider the pairing of neighboring
sites for the parent Kitaev spin-liquid (KSL) Hamiltonian to render the Majorana and the spin-1/2 Hilbert
spaces perfectly equivalent to each other. As a consequence, we demonstrate that this decoupling of the Kitaev
interaction in terms of the SO(3) Majorana fermions reproduces exactly the spectrum of the KSL model alone.
Then, by considering the effect of a local Kondo coupling JK in the model and decoupling it in terms of an order
parameter that physically must have a finite staggering phase, we obtain that the system undergoes a quantum
phase transition from a fractionalized Fermi liquid to a nematic triplet superconducting (SC) phase as JK is
increased. Depending on the model parameters, this SC phase can exhibit either Dirac points, Bogoliubov-Fermi
lines, or Bogoliubov-Fermi surfaces as nodal bulk manifolds. The surface states in this latter case are also
characterized by topologically protected antichiral edge modes. The SC phase breaks time-reversal symmetry
and exhibits a coexistence of a dominant odd-frequency pairing with a small even-frequency component for
electronic excitations localized on sites of the same sublattice of the system. Finally, we show that this SC phase
is in fact a pair-density-wave state, with Cooper pairs possessing a finite center-of-mass momentum in zero
magnetic field
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CARVALHO, Vanuildo S. de; TEIXEIRA, Rafael M. P. ; FREIRE, Hermann; MIRANDA, Eduardo. Odd-frequency pair density wave in the Kitaev-Kondo lattice model. Physical Review B, College Park, v. 103, p. 174512, 2021. DOI: 10.1103/PhysRevB.103.174512. Disponível em: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.174512. Acesso em: 31 maio 2023.