Machida T, Sun Y, Pyon S, Takeda S, Kohsaka Y, Hanaguri T, Sasagawa T, Tamegai T
RIKEN Center for Emergent Matter Science, Wako, Japan.
Department of Physics and Mathematics, Aoyama Gakuin University, Chuou-ku, Sagamihara, Japan.
Nat Mater. 2019 Aug;18(8):811-815. doi: 10.1038/s41563-019-0397-1. Epub 2019 Jun 17.
Majorana quasiparticles in condensed matter are important for topological quantum computing, but remain elusive. Vortex cores of topological superconductors may accommodate Majorana quasiparticles that appear as the Majorana bound state (MBS) at zero energy. The iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state that was investigated by scanning tunnelling microscopy (STM) studies, which suggest such a zero-energy vortex bound state (ZVBS). Here we present ultrahigh energy-resolution spectroscopic imaging (SI)-STM to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 ± 20 μeV, which constrained its MBS origin, and showed that some vortices host the ZVBS but others do not. We show that the fraction of vortices hosting the ZVBS decreases with increasing magnetic field and that local quenched disorders are not related to the ZVBS. Our observations elucidate the necessary conditions to realize the ZVBS, which paves the way towards controllable Majorana quasiparticles.
凝聚态物质中的马约拉纳准粒子对拓扑量子计算很重要，但仍然难以捉摸。拓扑超导体的涡旋核可能容纳马约拉纳准粒子，这些准粒子在零能量处表现为马约拉纳束缚态（MBS）。铁基超导体Fe(Se,Te)具有超导拓扑表面态，通过扫描隧道显微镜（STM）研究对其进行了探究，这些研究表明存在这种零能量涡旋束缚态（ZVBS）。在此，我们展示超高能量分辨率光谱成像（SI）-STM，以阐明Fe(Se,Te)中涡旋束缚态的性质。我们在0±20μeV处发现了ZVBS，这限制了其MBS起源，并表明一些涡旋拥有ZVBS而另一些则没有。我们表明，拥有ZVBS的涡旋比例随磁场增加而降低，并且局部淬火无序与ZVBS无关。我们的观察结果阐明了实现ZVBS的必要条件，这为可控的马约拉纳准粒子铺平了道路。
