title: Spin-resolved Andreev levels and parity crossings in hybrid superconductor-semiconductor nanostructures.
abstract: The physics and operating principles of hybrid superconductor-semiconductor devices rest ultimately on the magnetic properties of their elementary subgap excitations, usually called Andreev levels. Here we report a direct measurement of the Zeeman effect on the Andreev levels of a semiconductor quantum dot with large electron g-factor, strongly coupled to a conventional superconductor with a large critical magnetic field. This material combination allows spin degeneracy to be lifted without destroying superconductivity. We show that a spin-split Andreev level crossing the Fermi energy results in a quantum phase transition to a spin-polarized state, which implies a change in the fermionic parity of the system. This crossing manifests itself as a zero-bias conductance anomaly at finite magnetic field with properties that resemble those expected for Majorana modes in a topological superconductor. Although this resemblance is understood without evoking topological superconductivity, the observed parity transitions could be regarded as precursors of Majorana modes in the long-wire limit.
authors: SPSMS, CEA-INAC/UJF-Grenoble 1, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors: Eduardo J H
authors: EJ
authors: Lee
authors: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, Massachusetts 02138, USA.
authors: Xiaocheng
authors: X
authors: Jiang
authors: SPSMS, CEA-INAC/UJF-Grenoble 1, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors: Manuel
authors: M
authors: Houzet
authors: Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain.
authors: Ramón
authors: R
authors: Aguado
authors: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, Massachusetts 02138, USA.
authors: Charles M
authors: CM
authors: Lieber
authors: SPSMS, CEA-INAC/UJF-Grenoble 1, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors: Silvano
authors: S
authors: De Franceschi