Abstract
Direct detection of superconductivity has long been a key strength of point-contact Andreev reflection. However, its applicability to atomic-scale imaging is limited by the mechanical contact of the Andreev probe. To this end, we present a new method to probe Andreev reflection in a tunnel junction, leveraging tunneling spectroscopy and junction tunability to achieve quantitative detection of Andreev scattering. This method enables unambiguous assignment of superconducting origins of current-carrying excitations, as well as detection of higher order Andreev processes in atomic-scale junctions. We furthermore revealed distinct sensitivity of Andreev reflection to natural defects, such as step edges, even in classical superconductors. The methodology opens a new path to nano- and atomic-scale imaging of superconducting properties, including disordered superconductors and proximity to phase transitions.
| Original language | English |
|---|---|
| Pages (from-to) | 4042-4048 |
| Number of pages | 7 |
| Journal | Nano Letters |
| Volume | 22 |
| Issue number | 10 |
| DOIs | |
| State | Published - May 25 2022 |
Funding
Experimental measurements were supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division (W.K., P.M.). Experiments were carried out as part of the user project at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a US Department of Energy Office of Science User Facility. J.L.L. acknowledges the computational resources provided by the Aalto Science-IT project, and the financial support from the Academy of Finland Projects No. 331342 and No. 336243 and the Jane and Aatos Erkko Foundation.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Division of Materials Sciences and Engineering | |
| Academy of Finland | 336243, 331342 |
| Jane ja Aatos Erkon Säätiö |
Keywords
- Andreev reflection
- microscopy
- point-contact Andreev reflection
- superconductivity
- tunneling