Magnetic fluctuations in topological insulators with ordered magnetic adatoms: Cr on Bi2Se3from first principles

Abstract

We consider a system consisting of a topological insulator with an array of magnetic adatoms interacting with the surface states of electrons. We find that the indirect coupling of the magnetic impurities results in a ferromagnetic ordering of the magnetic moments and is also responsible for the unusual linear dispersion of the surface magnons. We also show that the interaction of magnons with surface electrons essentially renormalizes the electron energy spectrum. The renormalized spectrum is nonlinear and can be characterized by a negative effective mass of electrons and holes for any k = 0. The electron velocity near the Dirac point depends on the electron-magnon coupling.

Ab initio investigation of impurity-induced in-gap states in Bi2Te3 and Bi2Se3

“…These are the in-gap states central to our study, which were already observed for Cr (Mn) doped Bi 2 Se 3 (Bi 2 Te 3 ) in Refs. [39,40].…”

“…In this paper, we explore the impact of the bulk bands on the in-gap states present in magnetically doped topological insulators [31,39,40] This paper is organized as follows. In Sec.…”

Magnetic ordering in Cr-doped Bi 2 Se 3 thin films

“…For interstitial Cr the moment is ∼0.71 μ B , whereby both values have been calculated in a surface environment [22]. The magnetic moment of Cr 2+ ions in the low-spin configuration is 2 μ B ; however, this requires an octahedral crystal field larger than 2.5 eV [23].…”

Breaking time-reversal symmetry at the topological insulator surface by metal-organic coordination networks

“…On the one hand, ab initio calculations performed for ordered arrays of Co [34] and Cr [35] adatoms at the Bi 2 Se 3 surface predict FM ordering, out-of-plane magnetization, and, therefore, the DP splitting. This is in agreement with angle-resolved photoemission spectroscopy (ARPES) measurements of magnetically doped bismuth chalcogenide surfaces exhibiting a feature near the DP which resembles a gap [36,37].…”

“…Namely, to achieve the long-range FM order in the system of adatoms at the TI surface one has to organize their ordered arrays [14,34,35] and prevent them from diffusion [44,47] or intercalation inside the bulk or the van der Waals gaps [34,[51][52][53][54]. Lately, a type of system which may provide these conditions were successfully grown on metallic substrates-selfassembled metal-organic coordination networks (MOCNs) [55][56][57][58][59][60][61][62][63][64].…”