Fractional AC Josephson effect in a topological insulator proximitized by a self-formed superconductor
Ilan T. Rosen, Christie J. Trimble, Molly P. Andersen, Evgeny Mikheev, Yanbin Li, Yunzhi Liu, Lixuan Tai, Peng Zhang, Kang L. Wang, Yi Cui, M. A. Kastner, James R. Williams, David Goldhaber-Gordon
DOI 10.1103/PhysRevB.110.064511 · Physical Review B
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Abstract
A lateral Josephson junction in which the surface of a three-dimensional (3D) topological insulator (TI) serves as the weak link should support topologically protected excitations related to Majorana fermions. The resulting 4π-periodic current-phase relationship could be detected under high-frequency excitation by the suppression of odd Shapiro steps. Here, we demonstrate such devices through the self-formation of a Pd-Te superconducting layer from a telluride TI and observe suppressed first and third Shapiro steps. Other devices, including those where the Pd-Te layer is bolstered by an additional Al layer, show no suppression of Shapiro steps, a difference supported by simulations. Though we rule out the known trivial causes of suppressed Shapiro steps in our devices, we nevertheless argue that corroborating measurements and disorder-aware theoretical descriptions of these systems are needed before confidently claiming the observation of Majorana states.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Pd-Te Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.17 | Pressure not reported | midpoint |
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