近日，上海交通大学的贾金锋&李耀义及其研究小组与香港科技大学的刘军伟等人合作并取得一项新进展。经过不懈努力，他们揭示涡旋中多个马约拉纳零模杂化的特征。相关研究成果已于2024年8月28日在国际权威学术期刊《自然》上发表。

本文报道了超导拓扑晶体绝缘体SnTe（001）薄膜中涡旋束缚态的磁场响应。由于磁镜对称性，预计单个涡旋中会共存多个马约拉纳零模（MZMs）。研究人员使用配备有三轴矢量磁铁的扫描隧道显微镜发现，即使磁场较弱，单个涡旋中的零偏压峰（ZBP）也表现出明显的各向异性响应。当磁场平行于（110）型镜面时，ZBP可在（001）表面上稳健地扩展至长达约100nm的距离，否则将出现不对称分裂。

系统模拟表明，这种各向异性响应无法通过平凡的ZBP来重现。尽管由于实验中能量分辨率的限制，研究人员无法直接区分不同的MZMs，但实验测量与理论模拟之间的比较强烈支持对称保护的多MZMs的存在和杂化。这项研究工作展示了一种通过控制磁场方向来杂化不同MZMs的方法，并扩展了可用于调节拓扑态的MZM类型。

据悉，马约拉纳零模（Majorana zero modes，MZMs）是一种新出现的零能量拓扑准粒子，它们是其自身的反粒子。探测到的MZMs在空间上是分离的，且呈电中性，因此在超导体中产生MZMs之间的杂化极具挑战性。

附：英文原文

Title: Signatures of hybridization of multiple Majorana zero modes in a vortex

Author: Liu, Tengteng, Wan, Chun Yu, Yang, Hao, Zhao, Yujun, Xie, Bangjin, Zheng, Weiyan, Yi, Zhaoxia, Guan, Dandan, Wang, Shiyong, Zheng, Hao, Liu, Canhua, Fu, Liang, Liu, Junwei, Li, Yaoyi, Jia, Jinfeng

Issue&Volume: 2024-08-28

Abstract: Majorana zero modes (MZMs) are emergent zero-energy topological quasiparticles that are their own antiparticles. Detected MZMs are spatially separated and electrically neutral, so producing hybridization between MZMs is extremely challenging in superconductors. Here, we report the magnetic field response of vortex bound states in superconducting topological crystalline insulator SnTe (001) films. Several MZMs were predicted to coexist in a single vortex due to magnetic mirror symmetry. Using a scanning tunnelling microscope equipped with a three-axis vector magnet, we found that the zero-bias peak (ZBP) in a single vortex exhibits an apparent anisotropic response even though the magnetic field is weak. The ZBP can robustly extend a long distance of up to approximately 100nm at the (001) surface when the magnetic field is parallel to the (110)-type mirror plane, otherwise it displays an asymmetric splitting. Our systematic simulations demonstrate that the anisotropic response cannot be reproduced with trivial ZBPs. Although the different MZMs cannot be directly distinguished due to the limited energy resolution in our experiments, our comparisons between experimental measurements and theoretical simulations strongly support the existence and hybridization of symmetry-protected multiple MZMs. Our work demonstrates a way to hybridize different MZMs by controlling the orientation of the magnetic field and expands the types of MZM available for tuning topological states.

DOI: 10.1038/s41586-024-07857-4

Source: https://www.nature.com/articles/s41586-024-07857-4