Proximity-Induced Superconductivity in Monolayer MoS₂

Journal Article · 12 January 2020 · ACS Nano

DOI: https://doi.org/10.1021/acsnano.9b07475 · OSTI ID:1608034

Trainer, Daniel J. ^[1]; Wang, BaoKai ^[2]; Bobba, Fabrizio ^[3]; Samuelson, Noah ^[4]; Xi, Xiaoxing ^[5]; Zasadzinski, John ^[4]; Nieminen, Jouko  ^[6]; Bansil, Arun ^[2]; Iavarone, Maria  ^[5]

---

1. Temple Univ., Philadelphia, PA (United States); Temple University
2. Northeastern Univ., Boston, MA (United States)
3. Univ. of Salemo, Fisciano (Italy); Temple Univ., Philadelphia, PA (United States)
4. Illinois Inst. of Technology, Chicago, IL (United States)
5. Temple Univ., Philadelphia, PA (United States)
6. Northeastern Univ., Boston, MA (United States); Tampere Univ. of Technology (Finland)

Proximity effects in superconducting normal (SN) material heterostructures with metals and semiconductors have long been observed and theoretically described in terms of Cooper pair wave functions and Andreev reflections. Whereas the semiconducting N-layer materials in the proximity experiments to date have been doped and tens of nanometers thick, we present here a proximity tunneling study involving a pristine single-layer transition-metal dichalcogenide film of MoS₂ placed on top of a Pb thin film. Scanning tunneling microscopy and spectroscopy experiments together with parallel theoretical analysis based on electronic structure calculations and Green’s function modeling allow us to unveil a two-step process in which MoS₂ first becomes metallic and then is induced into becoming a conventional s-wave Bardeen–Cooper–Schrieffer-type superconductor. The lattice mismatch between the MoS₂ overlayer and the Pb substrate is found to give rise to a topographic moiré pattern. Even though the induced gap appears uniform in location, the coherence peak height of the tunneling spectra is modulated spatially into a moiré pattern that is similar to but shifted with respect to the moiré pattern observed in topography. The aforementioned modulation is shown to originate from the atomic-scale structure of the SN interface and the nature of local atomic orbitals that are involved in generating the local pairing potential. Our study indicates that the local modulation of induced superconductivity in MoS₂ could be controlled via geometrical tuning, and it thus shows promise toward the integration of monolayer superconductors into next-generation functional electronic devices by exploiting proximity-effect control of quantum phases.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Center for Complex Materials from First Principles (CCM); Temple Univ., Philadelphia, PA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-05CH11231; FG02-07ER46352; SC0004556; SC0012575
• OSTI ID: 1608034
• Journal Information: ACS Nano, Journal Name: ACS Nano Journal Issue: 3 Vol. 14; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English