Impurity states in the magnetic topological insulator 
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Peixoto, T. R. F.; Bentmann, Hendrik; Schreyeck, S.; Winnerlein, Martin; Seibel, Christoph; Maaß, Henriette; Al-Baidhani, Mohammed; Treiber, Katharina; Schatz, Sonja; Grauer, S.; Gould, C.; Βrunner, Karl; Ernst, A.; Molenkamp, Laurens W.; Reinert, F.

doi:10.1103/physrevb.94.195140

Cited by 41 publications

(48 citation statements)

References 55 publications

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“…12,13 In addition, a high V density of states near E F has been found using resonant (angular integrated) photoemission spectroscopy (AIPES) at the V L 3 edge and scanning tunneling spectroscopy. 20,21 This is in agreement with theoretically predicted nonzero V partial density of states (V-DOS) at E F .…”

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confidence: 89%

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

et al. 2017

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We combine low energy muon spin rotation (LE-µSR) and soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and electronic properties of magnetically doped topological insulators, (Bi,Sb)2Te3. We find that one achieves a full magnetic volume fraction in samples of (V/Cr)x(Bi,Sb)2−xTe3 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 L3 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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confidence: 89%

“…Several of the above effects potentially hinder the observation of the QAH effect at higher temperature 8,9,12,13,[19][20][21] and a deeper understanding of the interplay between the electronic and magnetic degrees of freedom in these materials is necessary in order to increase this temperature.…”

Section: 22mentioning

confidence: 99%

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

et al. 2017

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“…We point out that the impurityinduced in-gap states are strongly localized in the vicinity of the impurities, so that at larger distances the magnetic proximity effect could still lead to a gap in density of states (of the surface state). This could support a quantum anomalous Hall state [31,47,48].…”

Section: Discussionmentioning

confidence: 73%

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

et al. 2018

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We investigate in-gap states emerging when a single 3d transition metal impurity is embedded in topological insulators (Bi 2 Te 3 and Bi 2 Se 3 ). We use a combined approach relying on first-principles calculations and an Anderson impurity model. By computing the local density of states of Cr, Mn, Fe, and Co embedded not only in surfaces of Bi 2 Te 3 and of Bi 2 Se 3 but also in their bulk phases, we demonstrate that in-gap states originate from the hybridization of the electronic states of the impurity with bulk bands and not with the topological surface states as is usually assumed. This finding is analyzed using a simplified Anderson impurity model. These observations are in contradiction with the prevailing models used to investigate the magnetic doping of topological insulators [R. R. Biswas et al., Phys. Rev. B 81, 233405 (2010)], which attribute the origin of the in-gap states to the hybridization with the topological surface states.

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“…The QAH state, in contrast, can be formed in thin films of topological insulators (TI) even in the absence of magnetic field. [3][4][5][6][7][8][9][10] In this case the TRSB is induced by magnetic order attained by doping the TIs with transition metal elements like Cr, V, or Mn, [3][4][5][6][7][8]11,12 which open a mass gap Δ in the helical Dirac surface states. [13][14][15] In order to establish a TRSB topological state on a macroscopic scale the magnetic order should be long ranged and therefore a robust ferromagnetic (FM) state is believed to be a necessary condition for the experimental observation of the QAH effect with dissipationless chiral edge states.…”

Section: Introductionmentioning

confidence: 99%

Observation of superparamagnetism in coexistence with quantum anomalous Hall C = ±1 and C = 0 Chern states

et al. 2017

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Simultaneous transport and scanning nanoSQUID-on-tip magnetic imaging studies in Cr-(Bi,Sb) 2 Te 3 modulation-doped films reveal the presence of superparamagnetic order within the quantum anomalous Hall regime. In contrast to the expectation that a longrange ferromagnetic order is required for establishing the quantum anomalous Hall state, superparamagnetic dynamics of weakly interacting nanoscale magnetic islands is observed both in the plateau transition regions, as well as within the fully quantized C = ±1 Chern plateaus. Modulation doping of the topological insulator films is found to give rise to significantly larger superparamagnetic islands as compared to uniform magnetic doping, evidently leading to enhanced robustness of the quantum anomalous Hall effect. Nonetheless, even in this more robust quantum state, attaining full quantization of transport coefficients requires magnetic alignment of at least 95% of the superparamagnetic islands. The superparamagnetic order is also found within the incipient C = 0 zero Hall plateau, which may host an axion state if the top and bottom magnetic layers are magnetized in opposite directions. In this regime, however, a significantly lower level of island alignment is found in our samples, hindering the formation of the axion state. Comprehension and control of superparamagnetic dynamics is thus a key factor in apprehending the fragility of the quantum anomalous Hall state and in enhancing the endurance of the different quantized states to higher temperatures for utilization of robust topological protection in novel devices. 1-3 In the QH state the TRSB is induced by high magnetic field applied perpendicular to a high-mobility 2D electron gas. The QAH state, in contrast, can be formed in thin films of topological insulators (TI) even in the absence of magnetic field.3-10 In this case the TRSB is induced by magnetic order attained by doping the TIs with transition metal elements like Cr, V, or Mn,

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Impurity states in the magnetic topological insulator V:(Bi,Sb)2Te3

Cited by 41 publications

References 55 publications

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

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

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

Observation of superparamagnetism in coexistence with quantum anomalous Hall C = ±1 and C = 0 Chern states

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