Single-electron physics in barrier-defects coupled to ultrathin NbSe2

by Prof. Hadar Steinberg

The Hebrew University Of Jerusalem
at Condensed Matter Seminar

Mon, 10 Jun 2019, 11:30
Sacta-Rashi Building for Physics (54), room 207


The van-der-Waals fabrication method allows the realization of novel types of superconducting devices. In our work, we use van der Waals semiconductors as tunnel barriers separating the superconductor NbSe2 and normal counter electrodes. The devices exhibit a hard gap [1], which allows tracking sub-gap excitations such as vortex-bound states [2]. Van-der-Waals barriers often carry defects, which function as atomic-sized quantum dots. We find that barrier defects hybridize with the underlying superconductor. They form Andreev bound states (ABS) observed as sub-gap features in tunneling experiments - analogous to ABS observed in nanowires. We take advantage of the special properties of ultrathin NbSe2, where spin-orbit coupling keeps the superconducting gap stable upon application of parallel magnetic fields in the few Tesla regime. This gap stability allows the following of sub-gap features. These are found to split in energy, with a lower branch meeting at zero at a finite field. Such spectral evolution, associated with a singlet ground state, is consistent with a small charging energy. We further describe the observation of zero-energy states appearing at finite magnetic fields, and discuss their relation to the strong spin orbit term in the system [3].

1. T. Dvir, F. Massee, L. Attias, M. Khodas, M. Aprili, C. H. L. Quay & H. Steinberg. Spectroscopy of bulk and few-layer superconducting NbSe2 with van der Waals tunnel junctions. Nature Communications 9, 598 (2018).
2. T. Dvir, M. Aprili, C. H. L. Quay & H. Steinberg. Tunneling into the Vortex State of NbSe2 with van der Waals Junctions. Nano Lett. 18, 7845-7850 (2018).
3. T. Dvir, C. H. L. Quay, M. Aprili & H. Steinberg. Singlet ground state of Andreev bound states in van der Waals heterostructures. In Preparation (2019).

Created on 03-03-2019 by Meidan, Dganit (dganit)
Updaded on 03-06-2019 by Meidan, Dganit (dganit)