November 26, 2015 (15:00) the sixteenth  Schmidt seminar on superconductivity will take place in NUST «MISIS».

 

Title: «Odd-frequency pairing and Andreev bound states»

 

Presenter: Prof. Yukio Tanaka (Nagoya University, Japan)

 

Abstract

Superconductivity is a phenomenon where the macroscopic quantum coherence appears due to the pairing of electrons. The symmetry properties of the pairing, i.e., the parity and spin-singlet/spin-triplet, determine the physical properties of the superconducting state. Odd-frequency pairing originally discussed by Berezinskii as a bulk state. Although the bulk odd-frequency superconductor has not discovered experimentally, the importance of odd-frequency pairing amplitude has been recognized in ferromagnet / superconductor junctions and non-uniform systems. We have clarified that odd-frequency pair amplitude arises in the spatially non-uniform situation quite ubiquitously where bulk superconductor has a conventional even-frequency symmetry. Especially, it has been revealed that when the Andreev bound state (ABS) appears at the surface/interface of the sample, odd-frequency pairing is enhanced. It has been revealed that there are many exotic properties relevant to odd-frequency pairing like anomalous proximity effect in spin-triplet superconductor junctions. This anomalous proximity effect becomes prominent if we consider disordered normal (N) nano wire attached to a topologically nontrivial superconducting (S) one. The transport properties in superconducting nano-wire junctions show universal behaviors irrespective of the degree of disorder: the quantized zero-bias differential conductance at in NS junctions. The odd-frequency pairs exist wherever the Majorana fermions stay. We further discuss a strong relationship between Majorana fermions and odd-frequency Cooper pairs in several topological superconducting systems.

 

Seminar will be held in the Auditorium - B-636 (main building) NITU "MISIS", 6th floor.