0−π transition characteristic of the Josephson current in a carbon nanotube quantum dot

Lin Li; Bao-Bing Zheng; Wei-Qiang Chen; Hua Chen; Hong-Gang Luo; Fu-Chun Zhang

doi:10.1103/PhysRevB.89.245135

← Back to search

0−π transition characteristic of the Josephson current in a carbon nanotube quantum dot

Lin Li, Bao-Bing Zheng, Wei-Qiang Chen, Hua Chen, Hong-Gang Luo, Fu-Chun Zhang

DOI 10.1103/PhysRevB.89.245135 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

We consider the Josephson current through the carbon nanotube quantum dot with twofold orbital degeneracy connected by two superconductor leads. We show that the removal of orbital and spin degeneracies due to strong spin-orbit coupling and external magnetic field has a significant influence on the subgap Andreev bound states and the 0−π transition of the Josephson current. The 0−π transition point is determined by the level crossing of the lowest branch of the bound states and the Fermi level, and is given by [TK−ΔSO/2−(μ+1)B]/Δ∼1, with TK as the Kondo temperature, ΔSO the spin-orbit coupling, Δ the superconducting gap, μ the ratio of orbital moment and Bohr magneton, and B the Zeeman splitting loaded by the magnetic field. The interplay of the Kondo effect and superconductivity in such a quantum dot device provides a route to manipulate the 0−π transition of the Josephson current.