Observation of the Superconducting Proximity Effect from Surface States in SmB6/YB6 Thin Film Heterostructures via Terahertz Spectroscopy
Jonathan Stensberg, Xingyue Han, Seunghun Lee, Stephen A. McGill, Johnpierre Paglione, Ichiro Takeuchi, Charles L. Kane, Liang Wu
DOI 10.1103/PhysRevLett.130.096901 · Physical Review Letters
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Abstract
The ac conduction of epitaxially grown SmB6 thin films and superconducting heterostructures of SmB6/YB6 are investigated via time-domain terahertz spectroscopy. A two-channel model of thickness-dependent bulk states and thickness-independent surface states accurately describes the measured conductance of bare SmB6 thin films, demonstrating the presence of surface states in SmB6. While the observed reductions in the simultaneously measured superconducting gap, transition temperature, and superfluid density of SmB6/YB6 heterostructures relative to bare YB6 indicate the penetration of proximity-induced superconductivity into the SmB6 overlayer; the corresponding SmB6-thickness independence between different heterostructures indicates that the induced superconductivity is predominantly confined to the interface surface state of the SmB6. This study demonstrates the ability of terahertz spectroscopy to probe proximity-induced superconductivity at an interface buried within a heterostructure, and our results show that SmB6 behaves as a predominantly insulating bulk surrounded by conducting surface states in both the normal and induced-superconducting states in both terahertz and dc responses, which is consistent with the topological Kondo insulator picture.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YB6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 6.1 | Pressure not reported | unknown |
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