Fractional AC Josephson effect in a topological insulator proximitized by a self-formed superconductor

Abstract

A lateral Josephson junction in which the surface of a 3D topological insulator serves as the weak link should support topologically protected excitations related to Majorana fermions. The resulting $4\pi$-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 topological insulator, 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.

10 pages, 5 figures, plus Supplemental Material

References in corpus (15)

• The electronic properties of graphene
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures
• Epitaxy of Semiconductor-Superconductor nanowires
• Time-Reversal-Invariant $Z_4$ Fractional Josephson Effect
• Transparent Semiconductor-Superconductor Interface and Induced Gap in an Epitaxial Heterostructure Josephson Junction
• Work function of bulk-insulating topological insulator Bi2-xSbxTe3-ySey
• Proximity-induced superconductivity in (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ topological-insulator nanowires
• Half-Integer Shapiro Steps in a Short Ballistic InAs Nanowire Josephson Junction
• Quantum-Hall to Insulator Transition in Ultra-low-carrier-density Topological Insulator Films and a Hidden Phase of the Zeroth Landau Level
• Characterization of Shapiro steps in the presence of a 4π-periodic Josephson current
• Low-damage electron beam lithography for nanostructures on Bi${}_2$Te${}_3$-class topological insulator thin films
• Competing energy scales in topological superconducting heterostructures
• Origin of Hysteresis in a Proximity Josephson Junction

Cited by in corpus (8)

• A quantum dot in germanium proximitized by a superconductor
• Low-damage electron beam lithography for nanostructures on Bi${}_2$Te${}_3$-class topological insulator thin films
• Missing odd-order Shapiro steps do not uniquely indicate fractional Josephson effect
• Influence of disorder on antidot vortex Majorana states in 3D topological insulators
• Ubiquitous missing first Shapiro step in Al-InSb nanosheet Josephson junctions
• Unveiling Topological Hinge States in the Higher-Order Topological Insulator WTe${}_2$ Based on the Fractional Josephson Effect
• Gate-Tunable Ambipolar Josephson Current in a Topological Insulator
• Planar Hall supercurrent and δϕ-shift in the topological Josephson junction