Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators

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Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators

J. A. Krieger, Cui-Zu Chang, M.-A. Husanu, D. Sostina, A. Ernst, M. M. Otrokov, T. Prokscha, T. Schmitt, A. Suter, M. G. Vergniory, E. V. Chulkov, J. S. Moodera, V. N. Strocov, and Z. Salman

Phys. Rev. B 96, 184402 – Published 2 November 2017

Abstract

We combine low energy muon spin rotation ( $LE − μ SR$ ) and soft-x-ray angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and electronic properties of magnetically doped topological insulators, ( ${Bi, Sb)}_{2} {Te}_{3}$ . We find that one achieves a full magnetic volume fraction in samples of ${(V / Cr)}_{x} {(Bi, Sb)}_{2 - x} {Te}_{3}$ at doping levels $x ≳ 0.16$ . The observed magnetic transition is not sharp in temperature indicating a gradual magnetic ordering. We find that the evolution of magnetic ordering is consistent with formation of ferromagnetic islands which increase in number and/or volume with decreasing temperature. Resonant ARPES at the V $L_{3}$ edge reveals a nondispersing impurity band close to the Fermi level as well as V weight integrated into the host band structure. Calculations within the coherent potential approximation of the V contribution to the spectral function confirm that this impurity band is caused by V in substitutional sites. The implications of our results on the observation of the quantum anomalous Hall effect at mK temperatures are discussed.

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Received 8 August 2017

DOI:https://doi.org/10.1103/PhysRevB.96.184402

Physics Subject Headings (PhySH)

Magnetism

Magnetic semiconductors Thin films Topological insulators

Angle-resolved photoemission spectroscopy Density functional theory Muon spin relaxation & rotation

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

J. A. Krieger^1,2, Cui-Zu Chang^3,4, M.-A. Husanu^5,6, D. Sostina⁵, A. Ernst^7,8, M. M. Otrokov^9,10, T. Prokscha¹, T. Schmitt⁵, A. Suter¹, M. G. Vergniory^11,12, E. V. Chulkov^9,11,13, J. S. Moodera^3,14, V. N. Strocov⁵, and Z. Salman^1,*

¹Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
²Laboratorium für Festkörperphysik, ETH-Hönggerberg, CH-8093 Zürich, Switzerland
³Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
⁴Department of Physics, The Penn State University, University Park, Pennsylvania 16802, USA
⁵Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
⁶National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
⁷Institut für Theoretische Physik, Johannes Kepler Universität, A 4040 Linz, Austria
⁸Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
⁹Departamento de Física de Materiales UPV/EHU, Centro de Física de Materiales CFM - MPC and Centro Mixto CSIC-UPV/EHU, 20080 San Sebastián/Donostia, Spain
¹⁰Tomsk State University, pr. Lenina 36, 634050 Tomsk, Russia
¹¹Donostia International Physics Center, P. Manuel de Lardizabal 4, San Sebastián, 20018 Basque Country, Spain
¹²Department of Applied Physics II, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Apdo. 644, 48080 Bilbao, Spain
¹³Saint Petersburg State University, 198504 Saint Petersburg, Russia
¹⁴Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

^*Corresponding author: zaher.salman@psi.ch

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Issue

Vol. 96, Iss. 18 — 1 November 2017

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