Quantum transport in a normal metal/odd-frequency superconductor junction

Abstract

Recent experimental results indicate the possible realization of a bulk odd-frequency superconducting state in the compounds CeCu2Si2, and CeRhIn5. Motivated by this, we present a study of the quantum transport properties of a normal metal/odd-frequency superconductor junctions in a search for probes to unveil the oddfrequency symmetry. From the Eliashberg equations, we perform a quasiclassical approximation to account for the transport formalism of an odd-frequency superconductor with the Keldysh formalism. Specifically, we consider the tunneling charge conductance and tunneling thermal conductance. We find qualitatively distinct behaviour in the odd-frequency case as compared to the conventional even-frequency case, in both the electrical and thermal current. This serves as a useful tool to identify the possible existence of a bulk odd-frequency superconducting state.

Odd-frequency superconductivity induced by nonmagnetic impurities

“…The lack of odd-ω pairing for a classical impurity is a surprising result, since the literature is full of examples in which conventional superconducting pair amplitudes can be converted to odd-ω amplitudes by breaking almost any symmetry of the system. 1,[15][16][17][18][19][20][21][22][23][24][25][26][27][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] In particular, multiple previous works have found odd-ω pairing induced in conventional superconductors due to the breaking of spatial translation invariance at SN interfaces. 26,27 In the next section we take a first step toward reconciling this null result with previous research by adding some internal dynamics to the impurity.…”

“…While the thermodynamic stability of intrinsically odd-ω phases has, so far, only been discussed as a theoretical possibility, 7-14 significant progress has been made toward understanding the way in which odd-ω pairing can be induced by altering a system's conventional superconducting correlations through symmetry breaking. 1, The best established example is found in superconductorferromagnet (SF) junctions, 1,[15][16][17][18][19][20][21] in which experiments have observed key signatures of odd-ω spin-triplet pair correlations, [49][50][51] despite using conventional spin-singlet s-wave superconductors. The key property here is that both the interface and the bulk magnet break the symmetry between up and down spins, thus allowing for the conversion of spin-singlet to spin-triplet s-wave Cooper pairs at the interface, where the latter is necessarily odd in frequency.…”

Odd-frequency pairing and Kerr effect in the heavy-fermion superconductor UPt3

“…While the thermodynamic stability of intrinsically odd-ω phases is, so far, only discussed as a theoretical possibility, [16][17][18][19][20][21][22][23] significant progress has been made understanding systems with conventional superconductors in which odd-ω pairing can be induced by altering the na-tive superconducting correlations. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Well-established examples can be found in ferromagnet-superconductor junctions, [24][25][26][27][28][29][30] in which experiments have recently observed key signatures of odd-ω pair correlations. 43,44 For a modern review of this field see Ref.…”

Odd-frequency pairing in a superconductor coupled to two parallel nanowires

“…While the thermodynamic stability of intrinsically odd-ω phases has, so far, only been discussed as a theoretical possibility, [23][24][25][26][27][28][29][30] significant progress has been made understanding the way in which odd-ω pairing can be induced by altering a system's conventional superconducting correlations. 15, The best established example is found in ferromagnet-superconductor junctions, [31][32][33][34][35][36][37][38] in which experiments have observed key signatures of oddω spin-triplet pair correlations, 62-64 despite using conventional spin-singlet s-wave superconductors. Additionally, odd-parity odd-ω pair amplitudes been shown to be ubiquitous at interfaces between normal metals (N) and conventional spin-singlet superconductors (S), with close connections to observed McMillan-Rowell oscillations, as well as midgap Andreev resonances.…”