STM Study Of The Effects Of Magnetic Impurities On Sb(111) Surface

In recent years, topological materials have attracted considerable interests for application in the fields of spin electronic devices and quantum information processing. Their properties have been intensively studied by experiments and theories. As a new class of quantum materials, they are characterized by novel surface states with chiral spin texture. Meanwhile, the surface states following massless Dirac equation are protected by time-reversal (TR) symmetry and thereby are insensitive to spin-independent backscattering.One of the most important aspects in studying the topological states is to understand the interaction mechanism of its magnetic coupling with magnetic impurities in atomic scale as well as the resulting quantum phenomena. Since the topological states consist of antilocalized Dirac fermions where the spin and momentum are locked, it is still unknown how the topological states influence the quantum transports in comparison with those orthodox metallic electronic states. In this thesis, our studies are focused on the influence of magnetic impurities on the topological surface state of semimetallic Sb(111) with the simple configuration. The main results are shown as follows:(1) The local density of states of Co atoms adsorbed on Sb(111)are investigated by scanning tunneling spectroscopy (STS). A sharp peak locating near the Fermi energy is observed and originates from the Kondo effect. It reveals that the spin-polarized electronic clouds surrounding the Co atoms screen the magnetic moment of the magnetic impurities, and therefore the TR symmetry of topological surface states is protected from those magnetic scattering.(2) Standing waves on the Co/Sb(111) system are observed by energy resolved differential conductance mapping. By analyzing the scattering vectors, we clarify the scattering channels corresponding to forbidden backscattering for the surfaces with and without the Co adsorption. It implies that the TR symmetry of the topological surface states sustains for the magnetic interactions at our measurement condition.(3) The structures and electronic properties of CoPc molecules adsorbing on Sb(111) are investigated by scanning tunneling microscopy and STS. On top of CoPc molesules, a Kondo peak is also found near the Fermi level which implies that the TR symmetry is still not breaked.