Kavli ITS Workshop-Majorana Modes | 闻海虎

The Kavli ITS workshop on “Majorana Modes in Topological Superconductors” was held at the Kavli Institute for Theoretical Sciences (Kavli ITS) at UCAS in Beijing from January 8-11, 2019. The workshop mainly focuses on the realization and application of elusive Majorana modes in topological superconductors.

Majorana particles, which are their own antiparticles, have been of consider able interest for quantum computing in solid state systems since the zero-bias peak of the conductance was observed in the semiconductor nanowires. Now there are multiple experimental hints to support the potential existence of the Majorana states possessing zero energy. Since Majorana states can form qubits for quantum computation, once the Majorana states are able to be fully controlled and manipulated, the number of the Majorana qubits can be scalable to accelerate the speed of the quantum computation.

The scope of this workshop is to discuss the recent topics in Majorana bound states and Chiral Majorana edge modes in class D, aiming at promoting new collaborations among participants and seeking practical implementations to use Majorana modes for quantum computation. Furthermore, in the workshop, there will be a discussion session focusing on Majorana physics in the vortices of the topological superconductors.

图|闻海虎教授

题目：Vortex bound states and Majorana modes in FeTe_0.55Se_0.45 and Bi₂Te₃ / FeTe_0.55Se_0.45

报告人：闻海虎

单位：南京大学

时间：2019年1月8日-11日

地点：卡弗里理论科学研究所

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报告摘要

By measuring the spatial evolution of tunnelling spectra on the surface of FeTe_0.55Se_0.45, we observed the long sought discrete Caroli-de Gennes-Matricon bound states within some vortex cores. By analyzing the energies of thelowest level and the interval between the energy levels, we found that the ironbased superconductor FeTe_0.55Se_0.45 has the shallow bandwith the Fermi energy of about 5-20 meV, indicating the possibility of acrossover from BEC-BCS. Furthermore we have measured the vortex core boundstates on many other vortices in different areas and/or different samples, andfound that, in some vortices there is a strong bound state peak locating atzero energy. With the rather symmetric shape at the gap edge, we would conclude that it may correspond to the Majorana mode. With increase the magnetic field, the zero energy mode of the vortices locating at the same position is systematically suppressed. Meanwhile, we also find that the probability of observing the zero energy mode decreases with increasing the magnetic field. We find no clear connection between the surface concentration of Te/Se ratio. By increasing temperature, the zero energy mode is suppressed quickly and merged into the side peak in the occupied state at about 4K.

We deposit Bi₂Te₃ thin film on the FeTe_0.55Se_0.45 substrate and get the proximity induced superconductivity. By using the quasiparticle interference technique, we demonstrate clear evidence of twofold symmetry of the superconducting gap. The gap minimum is along one of the main crystalline axis following the so-called Δ_4y notation. This is also accompanied by the elongated vortex shape. Within the vortex core, along the stretcheddirection, a zero energy peak appears and stays until going out of the vortex. Our results reveal the direct evidence of superconductivity with two-fold symmetry in Bi₂Te₃ thin film.

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个人简介

闻海虎，现任南京大学教授，特聘教授, 美国物理学会会士。1993年10月回到中科院物理所工作；1996年-1998年在德国Ulm 大学从事洪堡学者研究计划；2005年-2010年担任科技部973项目“高温超导材料和物理研究”首席科学家；2013年入选"国家工程"，2014年担任科技部创新人才推进计划重点领域创新团队负责人。主要从事高温超导材料和物理问题研究，在包括Nature Physics，Nature Communications 在内的SCI 杂志上发表论文290余篇, 他人引用超过5000次。目前任Physica C, Philosophical Magazine, Chinese Physics Letters，《中国科学G辑》，《物理学进展》和《中国材料进展》等杂志的编委。

研究领域：探索合成新型超导材料；利用电输运，热力学，精密磁化和扫描隧道谱手段研究新型非常规超导体机理和磁通态物理；研究非常规电子态材料和物理性质，尤其关注具有非费米液体行为和量子临界特性的材料。

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