Coulomb blockade effects in a topological insulator grown on a high-T c cuprate superconductor
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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2020-10-14
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en
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npj Quantum Materials, Volume 5, issue 1
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.Description
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Rachmilowitz, B, Zhao, H, Ren, Z, Li, H, Thomas, K H, Marangola, J, Gao, S, Schneeloch, J, Zhong, R, Gu, G, Flindt, C & Zeljkovic, I 2020, ' Coulomb blockade effects in a topological insulator grown on a high-T c cuprate superconductor ', npj Quantum Materials, vol. 5, no. 1, 72 . https://doi.org/10.1038/s41535-020-00274-6