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Odd-frequency pairing in normal-metal/superconductor junctions
Tanaka, Y.
Tanuma, Y.
Golubov, A. A.
open access
American Physical Society, All rights reserved.
d-wave superconductivity
Green's function methods
superconductive tunnelling
We theoretically study the induced odd-frequency pairing states in ballistic normal-metal/superconductor (N/S) junctions where a superconductor has even-frequency symmetry in the bulk and a normal-metal layer has an arbitrary length. Using the quasiclassical Green's function formalism, we demonstrate that, quite generally, the pair amplitude in the junction has an admixture of an odd-frequency component due to the breakdown of translational invariance near the N/S interface where the pair potential acquires spatial dependence. If a superconductor has an even-parity pair potential (spin-singlet s-wave or spin-singlet d_xy-wave state), the odd-frequency pairing component with odd parity is induced near the N/S interface, while in the case of an odd-parity pair potential (spin-triplet p_x wave) the odd-frequency component with even parity is generated. We show that in conventional s-wave junctions, the amplitude of the odd-frequency pairing state is strongest in the case of a full-transparency N/S interface and is enhanced at energies corresponding to the peaks in the local density of states (LDOS). In p_x- and d_xy-wave junctions, the amplitude of the odd-frequency component on the S side of the N/S interface is enhanced at zero energy where the midgap Andreev resonant state (MARS) appears due to the sign change of the pair potential. The odd-frequency component extends into the N region and exceeds the even-frequency component at energies corresponding to the LDOS peak positions, including the MARS. At the edge of the N region the odd-frequency component is nonzero while the even-frequency one vanishes. We show that the concept of the odd-frequency pairing state plays a pivotal role to interpret a number of phenomena in nonuniform superconducting systems, like McMillan-Rowell and midgap Andreev resonance states.
American Physical Society
2007-08
eng
journal article
VoR
http://hdl.handle.net/2237/11289
https://nagoya.repo.nii.ac.jp/records/9507
https://doi.org/10.1103/PhysRevB.76.054522
1098-0121
PHYSICAL REVIEW B
76
5
054522
054522
https://nagoya.repo.nii.ac.jp/record/9507/files/PhysRevB_76_054522.pdf
application/pdf
1.1 MB
2018-02-20