Investigation of Interface-induced Superconductivity in Topological Insulator Heterostructures

by Dr Hemian Yi (Pennsylvania State University)

Tuesday 30 Apr 2024, 10:00 → 12:00 Asia/Shanghai

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Abstract

Over the last decade, the pursuit of the topological superconducting (TSC) phase has attracted a great deal of attention because of both the elegant physics of the subject and its potential application in topological quantum computations. The TSC phase has been proposed to be present in hybrid structures where a topological insulator (TI) film is proximally coupled to a conventional s-wave superconductor [1]. In the past years, we employed molecular beam epitaxy (MBE) to synthesize a series of TI-based heterostructures, including TI/superconductor [e.g., Bi₂Se₃/monolayer NbSe₂] and TI/non-superconducting material with interfacial superconductivity [e.g., (Bi,Sb)₂Te₃/FeTe and Cr-doped (Bi,Sb)₂Te₃/FeTe]. For Bi₂Se₃/monolayer NbSe₂ heterostructures, we found that the in-plane upper critical magnetic field of the superconducting Bi₂Se₃/monolayer NbSe₂ heterostructures is greatly reduced when the Rashba-type bulk conduction bands and surface states emerge, implying the crossover from the Ising- to Rashba-type superconductivity [2]. For (Bi,Sb)₂Te₃/FeTe and Cr-doped (Bi,Sb)₂Te₃/FeTe heterostructures, we found that interface-induced superconductivity emerges [3,4]. These TI/non-superconducting material heterostructures with interfacial superconductivity may also host the TSC phase because they fulfill the two essential ingredients of TSC, i.e. topological and superconducting orders [1]. The MBE-grown (Bi,Sb)₂Te₃/FeTe and Cr-doped (Bi,Sb)₂Te₃/FeTe heterostructures with atomically sharp interfaces will advance the fundamental inquiries into Majorana physics in hybrid devices and may provide an alternative approach for the exploration of the TSC phase.

References:
[1] Fu et al, Phys. Rev. Lett. 100, 096407(2008) 
[2] Yi et al, Nature Mater. 21, 1366(2022) 
[3] Yi et al, Nature Commun. 14, 7119 (2023)
[4] Yi et al, Science 383, 634(2024)

Biography

Dr. Hemian Yi is an assistant research professor in Prof. Cui-Zu Chang’s group in the Department of Physics at The Pennsylvania State University. He received his bachelor’s degree in 2009 from Shandong University and his Ph.D. degree in 2015 from the Institute of Physics, Chinese Academy of Sciences. Prior to joining Penn State, he conducted postdoctoral research at France National Synchrotron Facility- Synchrotron SOLEIL for two years. Dr. Yi’s research primarily focuses on emergent topological materials and their integration of superconductors, with the long-term goal of employing these platforms for scalable quantum information science and dissipationless quantum devices. The experimental tools in Dr. Yi’s research include molecular beam epitaxy (MBE) growth, electrical transport, and angle-resolved photoemission spectroscopy (ARPES) measurements. As of April 2024, Dr. Yi has published ~40 peer-reviewed papers. 10 first or co-first author papers include 1 in Science, 1 in Nature Materials, and 3 in Nature Communications.

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