Leggett Modes in Dirac Semimetals

Cuozzo, Joseph J.; Yu, Wenlong; Davids, Paul; Nenoff, Tina M.; Soh, Daniel B. S.; Pan, Wei; Rossi, Enrico

doi:10.48550/arxiv.2205.15995

Cited by 1 publication

(1 citation statement)

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“…Hybrid structures formed by a strong topological insulator (TI) and a superconductor (SC) have been theoretically predicted as a promising platform for realizing topological superconductivity. − Soon after the theoretical proposals, experiments showed that superconducting pairing can be induced on the surface states of three-dimensional (3D) TIs. − Experimental studies of Josephson junctions (JJs) based on 2D or 3D TI-SC heterostructures then showed signatures in the current voltage characteristic ( I – V ) under microwave radiation consistent with the presence of a topological superconducting state. − Over the past few years, a growing number of JJs with 3D TI weak links have been realized and displayed signs suggesting the establishment of a topological superconducting state. − Recently, several studies have provided further insight into the behavior of JJs based on topological materials, − and, in particular, have shown that signatures in the I – V properties often associated with the topological character of the superconducting state can also be observed in nontopological JJs. ,, …”

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confidence: 99%

Phase-Slip Lines and Anomalous Josephson Effects in Tungsten Nanoscale Cluster-Based Topological Insulator Nanobridges: Implications for Topologically Protected Qubits and Quantum Sensors

Qu,

Cuozzo,

Teslich

et al. 2024

ACS Appl. Nano Mater.

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Superconducting topological systems formed by a strong 3D topological insulator (TI) in proximity to a conventional s-wave superconductor (SC) have been intensely studied, as they may host Majorana zero modes. However, there are limited experimental realizations of TI-SC systems in which robust superconducting pairing is induced on the surface states of the TI and a topological superconducting state is established. Here, we fabricate a TI-SC system by depositing, via a focused ion beam, tungsten (W) nanoscale clusters on the surface of TI Bi 0.91 Sb 0.09 . We find that the resulting heterostructure supports phase-slip lines (PSLs) that act as effective Josephson junctions (JJs). We probe the response of the system to microwave radiation. We find that for some ac frequencies, and powers, the resulting Shapiro steps' structure of the voltage−current characteristic exhibits a missing first step and an unexpectedly wide second Shapiro step. The theoretical analysis of the measurements shows that the unusual Shapiro response arises from the interplay between a static JJ and a dynamic one and allows us to identify the conditions under which the missing first step can be attributed to the topological nature of the JJs formed by the PSLs. Our results suggest an approach to induce superconductivity in a TI, a route to realizing highly transparent topological JJs, and show how the response of superconducting systems to microwave radiation can be used to infer the dynamics of PSLs. Highly transparent topological junctions are promising candidates to realize vector field sensors with very high sensitivity. In addition, due to the nontrivial Berry phase of the TI's surface states such junctions can be in a topological state which is ideal to create topologically protected qubits.

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