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.
- Publication:
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Nature Nanotechnology
- Pub Date:
- January 2014
- DOI:
- arXiv:
- arXiv:1302.2611
- Bibcode:
- 2014NatNa...9...79L
- Keywords:
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- Condensed Matter - Mesoscale and Nanoscale Physics
- E-Print:
- 16 pages, 9 figures