Midgap edge states and pairing symmetry of quasi-one-dimensional organic superconductors

Abstract

The singlet s-, d-and triplet p-wave pairing symmetries in quasi-one-dimensional organic superconductors can be experimentally discriminated by probing the Andreev bound states at the sample edges. These states have the energy in the middle of the superconducting gap and manifest themselves as a zero-bias peak in tunneling conductance into the corresponding edge. Their existence is related to the sign change of the pairing potential around the Fermi surface. We present an exact self-consistent solution of the edge problem showing the presence of the midgap states for px-wave superconductivity. The spins of the edge state respond paramagnetically to a magnetic field parallel to the vector d that characterizes triplet pairing.

Paired chiral spin liquid with a Fermi surface inS=1model on the triangular lattice

“…This problem can be solved exactly for certain special cases of the interpolating gap profiles. 50,52 For example, a kink profile with ∆(y) = ∆[cos l(θ − π/2) − i tanh(y) sin l(θ − π/2)] yields the bound-state spectrum…”

“…49,50 For simplicity, let us choose a bulk potential of the form ∆(k) = ∆e ilθ(k) where l ∈ Z is the winding of the phase of the order parameter around the Fermi surface, and cos θ(k) = k x /|k|. A scattering state with incident angle θ results in an outgoing angle θ ′ = π − θ.…”

Theoretical prediction of the fractional ac Josephson effect in p- and d-wave superconductors

“…Since at D = 0 the Josephson junction consists of two semiinfinite uncoupled p x -wave superconductors, ψ L0 and ψ R0 are the wave functions of the surface midgap states [7] belonging to the left and right superconductor. Let us examine the properties of the midgap states.…”

“…[5] and discovered experimentally as a zero-bias conductance peak in tunneling between normal metals and superconductors (see review [6]). For the Q1D organic superconductors, the midgap states were theoretically predicted to exist at the edges perpendicular to the chains [7,8]. When two unconventional superconductors are joined together in a Josephson junction, their Andreev surface states hybridize to form Andreev bound states in the junction.…”

Nonlocality of zero-bias anomalies in the topologically trivial phase of Majorana wires

“…The semiconductor Majorana wire -the 1D version [15][16][17] of the semiconductorsuperconductor (SM-SC) heterostructure -represents a direct physical realization of the one-dimensional Kitaev model [5]. The observation of a sharp zero bias conductance peak (ZBP) in charge tunneling measurement has been proposed [15,[18][19][20][21][22] as a possible detection scheme for MFs localized near the ends of Majorana nanowires. The 1D SM-SC heterostructure and the associated ZBP measurements have recently attracted considerable experimental effort [23][24][25][26][27][28][29][30].…”