Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

D Kiphart,Y Harkavyi,M Wiesner,B Mróz,P Kuświk,J Szade,K Balin,S Jurga

doi:10.1038/s41598-021-02475-w

Abstract

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3.

Highlights

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI
Recent investigations of charge carrier dynamics in the vicinity of the critical temperature in iron-based high-temperature superconductors revealed a positive correlation between the strength of the electron–phonon coupling (EPC) and the critical temperature[57,58]
We can set a hypothesis that in the topological insulator grown on a high-temperature superconductor one can enhance the EPC in the TI

Summary

Introduction

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Hybrid structures of topological insulators (TI) and superconductors (SC) are an area of active interest due to the possibility of detecting Majorana modes and their potential applications in spintronics and quantum computing[1,2,3,4,5]. Such a hybrid device can be fabricated using classic low-temperature superconductors (LTSC) (e.g., Al, Nb) or high-temperature superconductors (HTSC) (e.g., YBa2Cu3O7-δ (YBCO) or Bi2Sr2Can−1CunO2n+4+δ (BSCCO)). The third proposes that the PS occurs due to Cooper pair tunnelling across the interface or due to the superconductor’s phonon-mediated pairing among surface electrons in the TI16

Methods

Results

Conclusion