Coulomb blockade effects in a topological insulator grown on a high-T c cuprate superconductor

Bryan Rachmilowitz, He Zhao, Zheng Ren, Hong Li, Konrad H. Thomas, John Marangola, Shang Gao, John Schneeloch, Ruidan Zhong, Genda Gu, Christian Flindt, Ilija Zeljkovic*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The evidence for proximity-induced superconductivity in heterostructures of topological insulators and high-Tc cuprates has been intensely debated. We use molecular-beam epitaxy to grow thin films of topological insulator Bi2Te3 on a cuprate Bi2Sr2CaCu2O8+x, and study the surface of Bi2Te3 using low-temperature scanning tunneling microscopy and spectroscopy. In few unit-cell thick Bi2Te3 films, we find a V-shaped gap-like feature at the Fermi energy in dI/dV spectra. By reducing the coverage of Bi2Te3 films to create nanoscale islands, we discover that this spectral feature dramatically evolves into a much larger hard gap, which can be understood as a Coulomb blockade gap. This conclusion is supported by the evolution of dI/dV spectra with the lateral size of Bi2Te3 islands, as well as by topographic measurements that show an additional barrier separating Bi2Te3 and Bi2Sr2CaCu2O8+x. We conclude that the prominent gap-like feature in dI/dV spectra in Bi2Te3 films is not a proximity-induced superconducting gap. Instead, it can be explained by Coulomb blockade effects, which take into account additional resistive and capacitive coupling at the interface. Our experiments provide a fresh insight into the tunneling measurements of complex heterostructures with buried interfaces.

Original languageEnglish
Article number72
Journalnpj Quantum Materials
Volume5
Issue number1
DOIs
Publication statusPublished - 1 Dec 2020
MoE publication typeA1 Journal article-refereed

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