Proximity induced signatures of elusive Bose metal phase in topological insulator- superconductor junction

TL;DR

This study explores the elusive Bose metal phase in superconductor-topological insulator junctions, observing unique transport signatures in nanoscale devices.

Contribution

First experimental observation of proximity-induced Bose metal phase signatures in SC-Bi2Te3 nanosheet junctions.

Findings

Resistive humps in magnetoresistance curves indicate the presence of a resistive metallic state.

Longer junctions show consistent hump features, while shorter ones suppress them.

Scaling analysis supports the emergence of a Bose metal phase in these junctions.

Abstract

The quantum metal state (QMS) occurring between the superconductor and insulator transition is often considered a Bose metal phase (BMP) whose understanding remains elusive and has been under debate even though studied for decades. To observe the BMP one needs to disrupt the phase coherence and search it into 2D amorphous, disorder, defective or nanoengineered superconducting materials. Superconductor -Topological insulator (SC-TI) junctions host the exotic nature of quasiparticles and are expected to show 2D superconductivity. Here, for the first time, we harness exotic SC-TI junctions investigating signatures of BMP and report proximity induced low temperature transport through superconductor-bismuth telluride (SC-Bi2Te3) nanosheet junctions. Transport data reveals superconducting effects in the nanosheets and the existence of the resistive metallic state with reentrant nature. We analysed the data to show the appearance of different quantum states. For longer junction lengths (1.1 & 0.78 μm), temperature-dependent resistive humps having similar peak heights and widths in the magnetoresistance (MR) curves were observed which were suppressed for smaller junction length (310 nm). The hump signatures in MR curves and scaling analysis of the data indicate the appearance of BMP. Our results suggest that SC-TI junctions exhibiting partial superconductivity are necessary to witness a peculiar metallic state resembling a BMP.

The online version contains supplementary material available at 10.1038/s41598-025-11256-8.

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