Rashba-type spin splitting from interband scattering in quasiparticle interference maps

Abstract

We have studied the BiCu 2 /Cu(111) surface alloy using low-temperature scanning tunneling microscopy and spectroscopy. We observed standing waves caused by scattering off defects and step edges. Different from previous studies on similar Rashba-type surfaces, we identified multiple scattering vectors that originate from various intraband as well as interband scattering processes. A detailed energy-dependent analysis of the standing-wave patterns enables a quantitative determination of band dispersions, including the Rashba splitting. The results are in good agreement with ARPES data and demonstrate the usefulness of this strategy to determine the band structure of Rashba systems. The lack of other possible scattering channels will be discussed in terms of spin conservation and hybridization effects. The results open new possibilities to study spin-dependent scattering on complex spin-orbit coupled surfaces.The Bychkov-Rashba effect lifts the spin-degeneracy at surfaces and interfaces in environments with a sizeable spin-orbit interaction [1]. Up to date, many different systems with various kinds of splitting strengths have been identified [2][3][4]. Its characteristic band dispersion is readily recognizable in angular resolved photoemission experiments and generally good agreement is achieved between theoretical calculations and experimentally observed electronic structures [4][5][6][7][8][9][10][11]. The Rashba parameter can also be extracted from the local density of states measured by scanning tunneling spectroscopy (STS) [12]. However,

Quasiparticle interference in ZrSiS: Strongly band-selective scattering depending on impurity lattice site

“…This may be expected (at least for non-magnetic defects which cannot impart angular-momentum to the final quasiparticle state) according to the same rationale as for suppression of spin-flip scattering which has been demonstrated in QPI measurements of spin-polarized bands in topological and Rashba systems (see Refs. [4][5][6][14][15][16]). However, here we stress that the general conservation on m remains an assumption, and is not strictly demonstrated by the results presented in this work: As each type of defect selectively scatters a certain sub-set of the CEC, and the underlying mechanism for selectivity is not yet known, the orbital character of the bands might be only incidental to the selectivity (and this might be true in general, not only in the current system).…”

“…The relative strength or suppression of various q-vectors is often used to infer attributes of the bands which are subject to selection rules governing scattering from initial to final states. Such selectivity has been exploited to explore the spin texture in spin-momentum-locked bands structures of topological and Rashba systems [4,[14][15][16][17][18], and the symmetry and momentum-dependent sign of the order parameter in unconventional superconductors [1,2,13]. Aside from the special case of scattering from magnetic flux vortices, which are known to have scattering properties qualitatively different from simple Coulomb potentials [13], impurities have until recently been treated as generic scattering centers, albeit with a relative scattering strength depending on the orbital character of the scattered band, or the different degrees to which impurity lattice sites coincide with a particular band's spatial charge density [16,17].…”

Enhancing and reducing the Rashba-splitting at surfaces by adsorbates: Na and Xe on Bi/Cu(111)

“…The surface alloy Bi/Cu(111) has been studied previously by ARPES [25,35,36], scanning tunneling spectroscopy [35,37], two-photon photoemission [36,38], spin-resolved photoemission [39] as well as ab initio electronic structure calculations [25,36,38]. In the following we briefly introduce the relevant features in the electronic structure of this compound and discuss in slightly more detail the quantitative applicability of the Rashba-model in equation (1).…”

Rashba splitting of graphene-covered Au(111) revealed by quasiparticle interference mapping

“…However, in the case of spin-split bands only scattering between states with the same spin polarization occurs, making it impossible to reconstruct the full spin-split band structure by analysis of QPI [21][22][23][24]. In particular cases, the presence of both spin-split and spin-degenerate surface state bands allows interband transitions, which yield the information about the Rashba splitting [25]. In Au(111), however, only spinconserved backscattering within the surface state is observed, which masks the actual spin splitting, hence necessitating a different approach for the local observation of the Rashba splitting.…”