Observation and characterization of the zero energy conductance peak in the vortex core state of FeTe${}_{0.55}$Se${}_{0.45}$

Abstract

The search for the Majorana fermions in condensed matter physics has attracted much attention, partially because they may be used for the fault-tolerant quantum computation. It has been predicted that the Majorana zero mode may exist in the vortex core of topological superconductors. Recently, many iron-based superconductors are claimed to exhibit a topologically nontrivial surface state, including Fe(Te,Se). Some previous experiments through scanning tunneling microscopy (STM) have found zero-bias conductance peaks (ZBCP) within the vortex cores of Fe(Te,Se). However, our early experimental results have revealed the Caroli-de Gennes-Matricon (CdGM) discrete quantum levels in about 20% vortices. In many other vortices, we observed a dominant peak locating near zero bias. Here we show further study on the vortex core state of many more vortices in FeTe${}_{0.55}$Se${}_{0.45}$. In some vortices, if we take a certain criterion of bias voltage window near zero energy, we indeed see a zero energy mode. Some vortices exhibit zero energy bound state peaks with relatively symmetric background, which cannot be interpreted as the CdGM discrete states. The probability for vortices showing the ZBCP lowers down with the increase of magnetic field. Meanwhile it seems that the presence and absence of the ZBCP has no clear relationship with the Te/Se ratio on the surface. Temperature dependence of the spectra reveals that the ZBCP becomes weakened with increasing temperature and disappears at about 4 K. Our results provide a confirmed supplementary to the early claimed zero energy modes within the vortex cores of Fe(Te,Se). Detailed characterization of these zero energy modes versus magnetic field, temperature and spatial distribution of Te/Se will help to clarify its origin.

References in corpus (13)

• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Paired states of fermions in two dimensions with breaking of parity and time-reversal symmetries, and the fractional quantum Hall effect
• Majorana Fermion Induced Resonant Andreev Reflection
• Evidence for Majorana bound state in an iron-based superconductor
• Observation of topological superconductivity on the surface of an iron-based superconductor
• Tunneling characteristic of a chain of Majorana bound states
• Topological superconductivity on the surface of Fe-based superconductors
• Quantum point contact as a probe of a topological superconductor
• Low-lying Quasiparticle Excitations around a Vortex Core in Quantum Limit
• Shallow pockets and very strong coupling superconductivity in FeSe_xTe_1-x
• Coexistence of incommensurate magnetism and superconductivity in Fe_{1+y}Se_xTe_{1-x}
• Strongly interacting Majorana fermions
• Electronic structure of topological superconductors in the presence of a vortex lattice

Cited by in corpus (5)

• Scalable Majorana vortex modes in iron-based superconductors
• Topological Superconductivity in an s-wave Superconductor and Its Implication to Iron-based Superconductors
• Topological orders competing for the Dirac surface state in FeSeTe surfaces
• Emergent vortex Majorana zero mode in iron-based superconductors
• Observation of Persistent Zero Modes and Superconducting Vortex Doublets in UTe${}_2$