Autor/a:
|
Sessi, Paolo; Rüßmann, P.; Bathon, Thomas; Barla, Alessandro; Kokh, K. A.; Tereshchenko, O. E.; Fauth, Kai; Mahatha, Sanjoy K; Valbuena, Miguel Ángel; Godey, Sylvie; Glott, F.; Mugarza, Aitor; Gargiani, Pierluigi; Valvidares, Manuel; Long, N. H.; Carbone, Carlo; Mavropoulos, Phivos; Blügel, Stefan; Bode, Matthias
|
Abstract:
|
Recently it has been shown that surface magnetic doping of topological insulators induces backscattering of Dirac states which are usually protected by time-reversal symmetry [Sessi, Nat. Commun. 5, 5349 (2014)10.1038/ncomms6349]. Here we report on quasiparticle interference measurements where, by improved Fermi level tuning, strongly focused interference patterns on surface Mn-doped Bi2Te3 could be directly observed by means of scanning tunneling microscopy at 4 K. Ab initio and model calculations reveal that their mesoscopic coherence relies on two prerequisites: (i) a hexagonal Fermi surface with large parallel segments (nesting) and (ii) magnetic dopants which couple to a high-spin state. Indeed, x-ray magnetic circular dichroism shows superparamagnetism even at very dilute Mn concentrations. Our findings provide evidence of strongly anisotropic Dirac-fermion-mediated interactions and demonstrate how spin information can be transmitted over long distances, allowing the design of experiments and devices based on coherent quantum effects in topological insulators. |