Yi Gao

Superconductivity in doped inversion-symmetric Weyl semimetals

We study theoretically the superconductivity in doped Weyl semimetals with an inversion symmetry based on the Bogoliubov-de Gennes equations. In principle, the two superconducting states, i.e., the zero momentum BCS-like pairing and the finite momentum Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing are competing in this kind of systems. Our self-consistent calculation indicates that the BCS-type state may be the ground state. The competition between these two pairing states is studied in detail through normal state Fermi surface and the finite energy spectral functions. Generally, the Fermi surface topology supports the FFLO pairing while the finite energy band structure favors the BCS-type pairing. We also study the physical properties and address the Majorana Fermions excitation in these two superconducting state respectively.

Model of vortex states in hole-doped iron-pnictide superconductors.

Based on a phenomenological model with competing spin-density-wave (SDW) and extended s-wave superconductivity, the vortex states in Ba(1-x)K(x)Fe2As2 are investigated by solving Bogoliubov-de Gennes equations. Our result for the optimally doped compound without induced SDW is in qualitative agreement with recent scanning tunneling microscopy experiment. We also propose that the main effect of the SDW on the vortex states is to reduce the intensity of the in-gap peak in the local density of states and transfer the spectral weight to form additional peaks outside the gap.

Quasiparticle states around a nonmagnetic impurity in electron-doped iron-based superconductors with spin-density-wave order

The quasiparticle states around a nonmagnetic impurity in electron-doped iron-based superconductors with spin-density-wave (SDW) order are investigated as a function of doping and impurity scattering strength. In the undoped sample, where a pure SDW state exists, two impurity-induced resonance peaks are observed around the impurity site and they are shifted to higher (lower) energies as the strength of the positive (negative) scattering potential (SP) is increased. For the doped samples, where the SDW order and the superconducting order coexist, the main feature is the existence of sharp in-gap resonance peaks, the positions and intensity of which depend on the strength of the SP and the doping concentration. In all cases, the local density of states exhibits clear

Testing the d*(x2-y2)-wave pairing symmetry by quasiparticle interference and Knight shift in BiS2-based superconductors

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Mixed-state effect on quasiparticle interference in iron-based superconductors

symmetry. We also note that, in the doped cases, the impurity will divide the system into two sublattices with distinct values of magnetic order. Here, we use the band structure of a two-orbital model, which considers the asymmetry of the As atoms above and below the Fe-Fe plane. This model is suitable to study the properties of the surface layers in the iron pnictides and should be more appropriate to describe the scanning tunneling microscopy experiments.

Electronic Structure around a Vortex Core in Iron-based Superconductors: Numerical Studies of a Two-orbital Model

The quasiparticle interference (QPI) patterns in BiS

Impurity-induced quasiparticle interference in the parent compounds of iron-pnictide superconductors

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Superfluid Density in the s ± -Wave State of Clean Iron-Based Superconductors

-based superconductors are theoretically investigated by taking into account the spin-orbital coupling and assuming the recently proposed

Spin dynamics in electron-doped iron pnictide superconductors

d^{*}_{x^{2}-y^{2}}

Charged-impurity-induced Majorana fermions in topological superconductors

-wave pairing symmetry. We found two distinct scattering wave vectors whose evolution can be explained based on the evolution of the constant-energy contours. The QPI spectra presented in this paper can thus be compared with future scanning tunneling microscopy experiments to test whether the pairing symmetry is