Manifestation of the odd-frequency spin-triplet pairing state in diffusive ferromagnet / superconductor junctions

TL;DR

This paper investigates how odd-frequency spin-triplet superconductivity influences the local density of states in diffusive ferromagnet/superconductor junctions, revealing conditions for zero energy peaks linked to specific pairing symmetries.

Contribution

It provides a detailed analysis of the manifestation of odd-frequency spin-triplet pairing states in ferromagnet/superconductor junctions using quasiclassical Green's functions, highlighting the physical origin of zero energy peaks.

Findings

OTE pairing enhances LDOS zero energy peaks

Exchange field influences pairing symmetry and LDOS features

ZEP splitting occurs with increased exchange field

Abstract

Using the quasiclassical Green's function formalism, we study the influence of the odd-frequency spin-triplet superconductivity on the local density of states (LDOS) in a diffusive ferromagnet (DF) attached to a superconductor. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli's principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. For each of these states, the pairing state in DF is studied. Particular attention is paid to the study of spin-singlet s-wave and spin-triplet p-wave superconductors as the examples of ESE and ETO superconductors. For spin-singlet case the magnitude of the OTE component of the pair amplitude is enhanced with the increase of the exchange field in DF. When the OTE component is dominant at low energy, the resulting LDOS in DF has a zero energy peak (ZEP). On the other hand, in DF / spin-triplet p-wave superconductor junctions LDOS has a ZEP in the absence of the exchange field, where only the OTE paring state exists. With the increase of the exchange field, the ESE component of the pair amplitude induced in DF is enhanced. Then, the resulting LDOS has a ZEP splitting. We demonstrate that the appearance of the dominant OTE component of the pair amplitude is the physical reason of the emergence of the ZEP of LDOS.