Spectroscopy of bulk and few-layer superconducting NbSe2 with van der Waals tunnel junctions

被引:95
作者
Dvir, T. [1 ]
Massee, F. [2 ]
Attias, L. [1 ]
Khodas, M. [1 ]
Aprili, M. [2 ]
Quay, C. H. L. [2 ]
Steinberg, H. [1 ]
机构
[1] Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel
[2] Univ Paris Saclay, Univ Paris Sud, CNRS, Lab Phys Solides,UMR 8502, Batiment 510, F-91405 Orsay, France
来源
NATURE COMMUNICATIONS | 2018年 / 9卷
关键词
CRITICAL FIELD; STATES; MODEL; DENSITY;
D O I
10.1038/s41467-018-03000-w
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra ;of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe2 devices at 70 mK. These exhibit two distinct superconducting gaps, the larger of which decreases monotonically with thickness and critical temperature. The spectra are analyzed using a two-band model incorporating depairing. In the bulk, the smaller gap exhibits strong depairing in in-plane magnetic fields, consistent with high out-of-plane Fermi velocity. In the few-layer devices, the large gap exhibits negligible depairing, consistent with out-of-plane spin locking due to Ising spin-orbit coupling. In the 3-layer device, the large gap persists beyond the Pauli limit.
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页数:6
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