Visualization of Unconventional Rashba Band and Vortex Zero Mode in Topopogical Superconductor Candidate AuSn${}_4$

Abstract

Topological superconductivity (TSC) is a promising platform to host Majorana zero mode (MZM) for topological quantum computing. Recently, the noble metal alloy AuSn${}_4$ has been identified as an intrinsic surface TSC. However, the atomic visualization of its nontrivial surface states and MZM remains elusive. Here, we report the direct observation of unconventional surface states and vortex zero mode at the gold (Au) terminated surfaces of AuSn${}_4$, by ultra-low scanning tunneling microscope/spectroscopy. Distinct from the trivial metallic bulk states at tin (Sn) surfaces, the Au terminated surface exhibits pronounced surface states near Fermi level. Our density functional theory calculations indicate that these states arise from unconventional Rashba bands, where two Fermi circles from different bands share identical helical spin textures, chiralities, and group velocities in the same direction. Furthermore, we find that although the superconducting gap, critical temperature, anisotropic in-plane critical field are almost identical on Au and Sn terminated surfaces, the in-gap bound states inside Abrikosov vortex cores show significant differences. The vortex on Sn terminated surfaces exhibits a conventional Caroli-de Gennes-Matricon bound state while the Au surface shows a sharp zero-energy core state with a long non-splitting distance, resembling an MZM in a non-quantum-limit condition. This distinction may result from the dominant contribution of unconventional Rashba bands near Fermi energy from Au terminated surface. Our results provide a new platform for studying unconventional Rashba band and MZM in superconductors.

17 pages, 4 figures

References in corpus (46)

• Topological insulators and superconductors
• Fault-tolerant quantum computation by anyons
• Non-Abelian Anyons and Topological Quantum Computation
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• New directions in the pursuit of Majorana fermions in solid state systems
• A generic new platform for topological quantum computation using semiconductor heterostructures
• Topological superconductors: a review
• Evidence for Majorana bound state in an iron-based superconductor
• Observation of topological superconductivity on the surface of an iron-based superconductor
• Topological Superconductivity in CuxBi2Se3
• Majorana mode in vortex core of Bi2Te3/NbSe2 topological insulator-superconductor heterostructure
• The Coexistence of Superconductivity and Topological Order in the Bi2Se3 Thin Films
• Three-dimensional charge density wave and robust zero-bias conductance peak inside the superconducting vortex core of a kagome superconductor CsV${}_3$Sb${}_5$
• Spin-pumping into surface states of topological insulator α-Sn, spin to charge conversion at room temperature
• Giant Rashba Splitting in CH3NH3PbBr3 Organic-Inorganic Perovskite
• Spin-Rotation Symmetry Breaking in the Superconducting State of CuxBi2Se3
• Discovery of Dirac Node Arcs in PtSn4
• Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te)
• Nearly quantized conductance plateau of vortex zero mode in an iron-based superconductor
• Robust and clean Majorana zero mode in the vortex core of high-temperature superconductor (Li0.84Fe0.16)OHFeSe
• Transmission of topological surface states through surface barriers
• Observation of half-integer level shift of vortex bound states in an iron-based superconductor
• Signature of Dispersing 1D Majorana Channels in an Iron-based Superconductor
• Magnetic Field Effects on Transport Properties of PtSn4
• Two-dimensional time-reversal-invariant topological superconductivity in a doped quantum spin Hall insulator
• Signature of a pair of Majorana zero modes in superconducting gold surface states
• Strong Superconducting Proximity Effect in Pb-Bi2Te3 Hybrid Structures
• First Principles Calculations for Topological Quantum Materials
• A new Majorana platform in an Fe-As bilayer superconductor
• Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs
• Extremely large magnetoresistance and Kohler's rule in PdSn4: a complete study of thermodynamic, transport and band structure properties
• Tunable vortex Majorana zero modes in LiFeAs superconductor
• Self-Assembled Nanowires with Giant Rashba-Type Band Splitting
• Vortex Lines in Topological Insulator-Superconductor Heterostructures
• Quasiparticle Interference Studies of Quantum Materials
• Robust gapless surface state and Rashba-splitting bands upon surface deposition of magnetic Cr on Bi${}_2$Se${}_3$
• Enhanced electron correlations in the new binary stannide PdSn4: a homologue of the Dirac nodal arc semimetal PtSn4
• Superconductivity in the surface state of noble metal gold and its Fermi level tuning by EuS dielectric
• Direct observation of topological surface state in the topological superconductor 2M-WS2
• Millikelvin scanning tunneling microscope at 20/22 T with a graphite enabled stick-slip approach and an energy resolution below 8$\mu$eV: Application to conductance quantization at 20 T in single atom point contacts of Al and Au
• Giant Inverse Rashba-Edelstein Effect: Application to Monolayer OsBi${}_2$
• Probing the topological surface states in superconducting Sn4Au single crystal: A magneto transport study
• Superconductivity in PtPb${}_4$ with Possible Nontrivial Band Topology
• Band structure, superconductivity and polytypism in AuSn${}_4$
• Ultrafast Carrier Relaxation Dynamics in a Nodal-Line Semimetal PtSn${}_4$
• Tunable vortex bound states in multiband CsV3Sb5-derived kagome superconductors