Direct probing of a large spin-orbit coupling in the FeSe superconducting monolayer on STO: Evidence for nontrivial topological states

Abstract

In condensed-matter physics spin-orbit coupling (SOC) is a fundamental physical interaction, which describes how the electrons' spin couples to their orbital motion. It is the source of a vast variety of fascinating phenomena in solids such as topological phases of matter, quantum spin Hall states, and many other exotic quantum states. Although in most theoretical descriptions of the phenomenon of high-temperature superconductivity SOC has been neglected, including this interaction can, in principle, revise the microscopic picture of superconductivity in these compounds. Not only the interaction leading to Cooper pairing but also the symmetry of the order parameter and the topological character of the involved states can be determined by SOC. Here by preforming energy-, momentum-, and spin-resolved spectroscopy experiments with an unprecedented resolution we demonstrate that while probing the dynamic charge response of the FeSe monolayer on strontium titanate, a prototype two dimensional high-temperature superconductor using slow electrons, the scattering cross-section shows a considerable spin asymmetry. We unravel the origin of the observed spin asymmetry by developing a model in which SOC is taken into consideration. Our analysis indicates that SOC in this two dimensional superconductor is rather strong. We anticipate that such a strong SOC can have several serious consequences on the electronic structures and can lead to the formation of topological states. Moreover, a sizable SOC can compete with other pairing scenarios and is crucial for the mechanism of high-temperature superconductivity.

15 pages, 4 figures. arXiv admin note: text overlap with arXiv:2210.02058

References in corpus (13)

• Non-Abelian Anyons and Topological Quantum Computation
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Introduction to topological superconductivity and Majorana fermions
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• Ubiquitous strong electron phonon coupling at the interface of FeSe/SrTiO3
• Topological Phases in the Single-Layer FeSe
• Superconducting Properties of the $s^{\pm }$-wave state: Fe-based superconductors
• Temperature Dependence of Magnetic Excitations: Terahertz Magnons above the Curie Temperature
• Lattice Dynamics of Ultrathin FeSe Films on SrTiO3
• Interfacial Electron-Phonon Coupling Constants Extracted from Intrinsic Replica Bands in Monolayer FeSe/SrTiO${}_3$
• On the phonon dispersion relation of single-crystalline $\beta$--FeSe
• Enhanced superconductivity in FeSe/SrTiO${}_3$ from the combination of forward scattering phonons and spin fluctuations
• Theory of spin-polarized high-resolution electron energy loss spectroscopy from nonmagnetic surfaces with a large spin-orbit coupling

Cited by in corpus (8)

• Nematic Bogoliubov Fermi surfaces from magnetic toroidal order in FeSe${}_{1-x}$S${}_x$
• Giant spatial anisotropy of magnon lifetime in altermagnets
• Nonlinear optical responses in superconductors under magnetic fields: quantum geometry and topological superconductivity
• Unraveling the Complexity of the Dzyaloshinskii-Moriya Interaction in Layered Magnets: The Full Magnitude and Chirality Control
• Direct evidence of a charge depletion region at the interface of Van der Waals monolayers and dielectric oxides: The case of superconducting FeSe/STO
• Unique properties of the optical activity in noncentrosymmetric superconductors: sum rule, missing area, and relation with the superconducting Edelstein effect
• Ubiquity of the spin-orbit induced magnon nonreciprocity in ultrathin ferromagnets
• Temperature evolution of the Fermi surface of the FeSe monolayer on SrTiO${}_3$