STM Study Of Spin-orbit Polaron In Magnetic Weyl Semimetal Co₃Sn₂S₂

The defect engineering of magnetic quantum materials and the regulation of local spins are expected to build practical quantum spin devices in the future,which is currently one of the hotspots in condensed matter physics research.The transition metal based kagome lattice compounds have merged recently as a novel materials platform for unveiling and exploring the rich and unusual physics of geometric frustration,correlation and magnetism,and the topological behaviors of the quantum electronic states.These are layered crystalline materials where the transition metal elements occupy the vertices of the two-dimensional network of corner-sharing triangles,supporting electronic band structures with Dirac crossings and nearly flat bands with strong spin-orbit coupling.These prototype materials exhibit different magnetic ground states,such as ferromagnetic,antiferromagnetic and paramagnetic.Studying the relationship between magnetism and topological nature in such materials can help researchers understand the physical properties of magnetic quantum materials.Defect excitations at atomic vacancies and adatoms,which are known to provide deeper understanding and reveal new physical properties of correlation topological materials,have yet to be explored in these kagome lattice materials.In light of this,using spin-polarized scanning tunneling microscopy(SP-STM)and atomic force microscopy(AFM),we focus on the local excitation in the magnetic Weyl semimetal Co₃Sn₂S₂ and the Kondo resonance manipulation of magnetic molecules.1.Localized spin-orbit polaron from single vacancy of magnetic Weyl semimetal Co₃Sn₂S₂ are studied.The bound magnetic polarons nucleated around single S-vacancies are found in nearly non-magnetic S surface by spin-polarized STM.They emerged as bound states in the conductance map with a three-fold rotation symmetry.Applying external magnetic fields up to±6 T normal to the surface reveals that the binding energy of the localized magnetic polaron linearly increases as a function of the field magnitude regardless of the field direction.This anomalous response indicates dominant orbital magnetization contribution to the local magnetic moment.Besides,the appreciable magneto-elastic coupling around the S-vacancy is captured.2.The electronic structure of the intrinsic defects adsorbed on the cleavage surface in the nominal Co₃Sn₂S₂ was systematically studied.The defects contribute sharp contrast to the local electronic structure and behaves typical localization states.The asymmetric bonding mode of the impurities to the surface atoms was found.The response of the electronic structure of intrinsic impurities to external magnetic fields was studied.This work has enriched the understanding of the electronic structure as well as element composition of the intrinsic impurities of this material in related field and challenged existed work.3.Using superconducting Nb tip,the two adsorption configurations of FePc molecules on Au(111)are distinguished.Both of them present a"cross"-like topography with Fe atoms at the center.In the d I/d V spectrum,the type I configuration shows significant Kondo resonance characteristics,while the other shows the inelastic tunneling process with the participation of vibration modes.By controlling the tunnel junction barrier conductance,Switch between the Kondo effect and the IETS mode under narrow conductance window is realized.This operation is highly reversible and reproducible.Furthermore,by picking up the FePc molecule to the top of the superconducting Nb tip,the Yu-Shiba-Rusinov state appears in the superconducting energy gap.The discovery of the localized SOP opens a novel route for manipulating the magnetic order and the topological phenomena in Weyl semimetal Co₃Sn₂S₂.Controlled engineering of the SOPs may pave the way toward practical application in functional quantum devices.On the other hand,the in-situ reversible switch of Kondo effect in single magnetic molecule is a new approach to the regulation of physical properties of single-molecule devices.