Interplay between ferromagnetism, surface states, and quantum corrections in a magnetically doped topological insulator

Abstract

The breaking of time-reversal symmetry by ferromagnetism is predicted to yield profound changes to the electronic surface states of a topological insulator. Here, we report on a concerted set of structural, magnetic, electrical and spectroscopic measurements of \MBS thin films wherein photoemission and x-ray magnetic circular dichroism studies have recently shown surface ferromagnetism in the temperature range 15 K $\le T\le 100$ K, accompanied by a suppressed density of surface states at the Dirac point. Secondary ion mass spectroscopy and scanning tunneling microscopy reveal an inhomogeneous distribution of Mn atoms, with a tendency to segregate towards the sample surface. Magnetometry and anisotropic magnetoresistance measurements are insensitive to the high temperature ferromagnetism seen in surface studies, revealing instead a low temperature ferromagnetic phase at $T\lesssim 5$ K. The absence of both a magneto-optical Kerr effect and anomalous Hall effect suggests that this low temperature ferromagnetism is unlikely to be a homogeneous bulk phase but likely originates in nanoscale near-surface regions of the bulk where magnetic atoms segregate during sample growth. Although the samples are not ideal, with both bulk and surface contributions to electron transport, we measure a magnetoconductance whose behavior is qualitatively consistent with predictions that the opening of a gap in the Dirac spectrum drives quantum corrections to the conductance in topological insulators from the symplectic to the orthogonal class.

To appear in Phys. Rev. B

References in corpus (5)

• Topological Field Theory of Time-Reversal Invariant Insulators
• Quantized Anomalous Hall Effect in Magnetic Topological Insulators
• The development of ferromagnetism in the doped topological insulator Bi2-xMnxTe3
• Origin and control of high-temperature ferromagnetism in semiconductors
• Surface magnetic ordering in topological insulators with bulk magnetic dopants

Cited by in corpus (14)

• Surface State Magnetization and Chiral Edge States on Topological Insulators
• Giant Anisotropic Magnetoresistance in a Quantum Anomalous Hall Insulator
• Quantum anomalous Hall effect in ferromagnetic transition metal halides
• Dimensional Crossover Induced Topological Hall Effect in a Magnetic Topological Insulator
• Weak localization and weak anti-localization in topological insulators
• Spin- and angle-resolved photoemission on topological materials
• Observation of Distinct Bulk and Surface Chemical Environments in a Topological Insulator under Magnetic doping
• Low temperature saturation of phase coherence length in topological insulators
• Infrared electrodynamics and ferromagnetism in the topological semiconductors Bi${}_2$Te${}_3$ and Mn-doped Bi${}_2$Te${}_3$
• Crossover Between Weak Antilocalization and Weak Localization and Electron-Electron Interaction in Few-Layer WTe${}_2$
• Small Fermi Surfaces and Strong Correlation Effects in Dirac Materials with Holography
• Nanoscale $\beta$-Nuclear Magnetic Resonance Depth Imaging of Topological Insulators
• Magnetic properties of Mn-doped Bi${}_2$Se${}_3$ topological insulators: ab initio calculations
• Bulk Saturable absorption in Topological Insulator thin Films