Andreev Reflection studies on NbSe<sub>2</sub> with normal and superconducting tip

ORAL

Abstract

Tunneling Andreev Reflection (TAR) spectroscopy emerges as a powerful technique for probing superconducting order parameter symmetry in both conventional and unconventional superconductors through decay rate measurements of Andreev process. Unlike traditional Point Contact Andreev Reflection (PCAR), TAR achieves spatial resolution by operating from near-contact to tunneling regimes, enabling local mapping of excess conductance across surface features. This capability is demonstrated through spatial mapping of charge density wave domains in NbSe2, revealing distinct variations in Andreev reflection signatures. Furthermore, using a NbSe2 flake-terminated tip to probe the NbSe2 surface, the study observes characteristic signatures of Josephson currents and subharmonic gap features attributing to multiple Andreev reflections.

*This research was sponsored by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. SPM experiments were carried at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, a US DOE Office of Science User Facility.

–

Publication: 1. Ko, W., Song, S. Y., Yan, J., Lado, J. L., & Maksymovych, P. (2023). Atomic-Scale Andreev Probe of Unconventional Superconductivity. Nano Letters, 23(17), 8310-8318.
2. Ko, Wonhee, Jose L. Lado, and Petro Maksymovych. "Noncontact Andreev Reflection as a Direct Probe of Superconductivity on the Atomic Scale." Nano Letters 22.10 (2022): 4042-4048.
3. Ko, Wonhee, Eugene F. Dumitrescu, and Petro Maksymovych. "Statistical detection of Josephson, Andreev, and single quasiparticle currents in scanning tunneling microscopy." Physical Review Research 3.3 (2021): 033248.

Presenters

  • Nirjhar Sarkar

    • Oak Ridge National Laboratory

Authors

  • Nirjhar Sarkar

    • Oak Ridge National Laboratory

  • Wonhee Ko

    • University of Tennessee

  • Petro Maksymovych

    • Oak Ridge National Laboratory

  • Benjamin J Lawrie

    • Oak Ridge National Laboratory