Dirac gap opening and Dirac-fermion-mediated magnetic coupling in antiferromagnetic Gd-doped topological insulators and their manipulation by synchrotron radiation

Shikin, A. M.; Estyunin, D. A.; Surnin, Yu. I.; Королева, А. В.; Shevchenko, E. V.; Кох, К. А.; Tereshchenko, O. E.; Kumar, Shiv; Schwier, Eike F.; Shimada, Kenya; Yoshikawa, Tomohiro; Saitoh, Y.; Takeda, Yukiharu; Kimura, Akio

doi:10.1038/s41598-019-41137-w

Cited by 28 publications

(26 citation statements)

References 57 publications

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“…Recent breakthrough in such direction has been made thanks to the growth technology of 2D ferromagnetic (FM) semiconductors [15,16] and more importantly, intrinsic 3D magnetic TI MnBi2Te4, a magnetic version in analogy to time-reversal (T) preserved TI Bi2Te3 stacked by Van der Waals (VdW) connected sublayers. It is predicted and soon experimentally verified that MnBi2Te4 in its magnetic ground state is a Z2 antiferromagnetic (AFM) TI protected by a combined symmetry of T and a fractional translation operation [17][18][19][20][21].…”

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confidence: 99%

Rational Design Principles of the Quantum Anomalous Hall Effect in Superlatticelike Magnetic Topological Insulators

et al. 2019

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As one of paradigmatic phenomena in condensed matter physics, the quantum anomalous Hall effect (QAHE) in stoichiometric Chern insulators has drawn great interest for years. By using model Hamiltonian analysis and first-principle calculations, we establish a topological phase diagram and map on it with different two-dimensional configurations, which is taken from the recently-grown magnetic topological insulators MnBi4Te7 and MnBi6Te10 with superlattice-like stacking patterns. These configurations manifest various topological phases, including quantum spin Hall effect with and without time-reversal symmetry, as well as QAHE. We then provide design principles to trigger QAHE by tuning experimentally accessible knobs, such as slab thickness and magnetization. Our work reveals that superlattice-like magnetic topological insulators with tunable exchange interaction serve as an ideal platform to realize the long-sought QAHE in pristine compounds, paving a new avenue within the area of topological materials.

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Rational Design Principles of the Quantum Anomalous Hall Effect in Superlatticelike Magnetic Topological Insulators

et al. 2019

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“…Для анализа электронной структуры в области энергетической щели в точке Дирака и ее зависимости от температуры и уровня магнитного легирования обычно используется метод фотоэлектронной (ФЭ) спектроскопии с угловым разрешением (ФЭСУР), см. например [5][6][7][8][9][10][11][12][13][14][15][16][17]. При этом зачастую оказывается, что измеряемые дисперсионные картины для ряда магнитных ТИ демонстрируют слабую зависимость от температуры.…”

Section: Introductionunclassified

“…При этом зачастую оказывается, что измеряемые дисперсионные картины для ряда магнитных ТИ демонстрируют слабую зависимость от температуры. В измеряемых ФЭСУР-дисперсиях наблюдается сохранение щели в точке Дирака выше температуры Кюри или Нееля, для ферромагнитных (ФМ) и антиферромагнитных (АФМ) ТИ, т. е. при нарушении дальнодействующего магнитного упорядочения [7][8][9][11][12][13][14][15][16][17].…”

Section: Introductionunclassified

“…В литературе делались попытки объяснения слабой температурной зависимости щели в точке Дирака и ее наблюдения выше температуры магнитного упорядочения, например, в работах [7,[14][15][16][17][18][19][20]. При этом, с одной стороны, высказывались предположения о немагнитной природе щели (за счет эффектов " непересечения" элек-тронных состояний, открывающих гибридизационную немагнитную щель) [17][18][19] или повышенной поверхностной температуры Кюри [20].…”

Section: Introductionunclassified

“…При этом, с одной стороны, высказывались предположения о немагнитной природе щели (за счет эффектов " непересечения" элек-тронных состояний, открывающих гибридизационную немагнитную щель) [17][18][19] или повышенной поверхностной температуры Кюри [20]. С другой стороны, открытие щели связывалось с эффектами индуцированной намагниченности, обусловленной нескомпенсированной спиновой аккумуляцией и соответствующим спин-торк-эффектом, возникающих благодаря неэквивалентному фотовозбуждению электронов с противоположных ветвей дираковского конуса электронных состояний [7,[14][15][16]. При этом была выявлена зависимость щели в точке Дирака, наблюдаемая в ФЭСУР от энергии фотонов и поляризации излучения, которые не могут быть объяснены в рамках перечисленных выше эффектов.…”

Section: Introductionunclassified

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Механизм открытия щели в точке Дирака в электронном спектре Gd-допированного топологического изолятора

Шикин¹,

Естюнин²,

Королева³

et al. 2020

Физика Твердого Тела

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The electronic structure of magnetically-doped TI with stoichiometry Bi1.09Gd0.06Sb0.85Te3 in the region of the Dirac point has been studied in detail by angle-resolved photoelectron spectroscopy (ARPES) at various temperatures (above and below the Néel temperature, 1-35 K) and different polarizations of synchrotron radiation. It has shown that the energy gap in photoemission spectra opens at the Dirac point and remains open above the temperature of the long-range magnetic ordering, Tn. Measurements of magnetic properties by the superconducting magnetometry method (SQUID) have shown antiferromagnetic ordering with a transition temperature to the paramagnetic phase equal to 8.3 K. Study of the temperature dependence of the Dirac cone state intensity at the Г point by ARPES has confirmed the magnetic transition and has shown a possibility of its indication directly from photoemission spectra. A more detailed analysis of the splitting between the upper and lower Dirac cone states (i.e. the energy gap) at the Dirac point in the photoelectron spectra has shown the dependence of the measured gap on the synchrotron radiation polarization (about 28-30 meV for p-polarization and 22-25 meV for circularly polarized radiation of opposite chirality). The mechanism of opening the gap at a Dirac point above the Tn was proposed due to the “pairing” of the Dirac fermions with opposite momentum and spin orientation as a result of their interaction with the spin texture generated by photoemission in the region of the photoemission hole on a magnetic impurity atom (Gd). It was shown that the gap at the Dirac point, measured above Tn, is dynamic and is formed directly during photoemission process. At the same time, the origin of the gap remains magnetic (even when the long-range magnetic ordering is destroyed) and is associated with the properties of the magnetic topological insulator that determines a practically unchanged size of the gap above Tn. The dynamic origin of the generated gap is confirmed by the dependence of its magnitude on the polarization of synchrotron radiation.

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Magnetic Topological Insulator Heterostructures: A Review

Liu

Hesjedal

2021

Advanced Materials

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Chern number corresponds to the occupancy of discrete Landau levels, which can be varied by tuning the Fermi energy via a gate voltage. It further corresponds to the number of dissipationless conduction channels in the gapless edge state of the quantum Hall insulator that is insulating in the bulk in high magnetic fields.After observing the quantum version of the Hall effect, the natural question to ask is if there is also a quantized version of the anomalous Hall effect (AHE), commonly observed in ferromagnets. This quantum anomalous Hall effect (QAHE) would then be observable in the absence of external fields. The QAHE was initially proposed to arise in 2D honeycomb or kagome lattices, such as monolayer graphene, that host a non-zero out-of-plane magnetic flux density, but zero net flux in each unit cell. [8,9] Later, it was also proposed that the QAHE may be found in Hg 1−y Mn y Te quantum wells without an external magnetic field, in which the effect arises purely due to the spin polarization of the Mn atoms. [10] However, the experimental realization of the QAHE was not reported until 2013, when transport in 3D topological insulators (TIs) doped with magnetic impurities was studied. TIs refer to a class of materials that is insulating in the bulk, but which possess topologically protected conducting surface states. Right from the start, the field was (see refs. [6,11-17]), and continues to be (see refs. [18-20]), to a large degree driven by theory. Common examples of 3D TIs are rhombohedral Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 . [15] The surface state of a TI consists of two linearly dispersing states connecting the bulk conduction and valence bands. The two states cross at one point in reciprocal space, the Dirac point (Figure 1a). The charge carriers in this band structure are massless fermions, which are described by the relativistic Dirac equation. [15] Due to the strong spin-orbit coupling (SOC) in these materials, surface electron spins are locked to their momentum, forming dissipationless, counter-propagating conduction channels in the surface state.By introducing magnetism to a TI, either by impurity doping with magnetic elements, by proximity coupling to a magnetic insulators (MIs), or other magnetic layers, time-reversal symmetry (TRS) can be broken. TRS breaking can induce a bandgap in the surface states, leading to the realization of the QAHE which is characterized by 1D chiral edge conduction in zerofield at remanence, as shown in Figure 1. The Chern number, here being +1 or -1, corresponds to the direction of the spinmomentum locked edge current that can be flipped by a (small) external field. Using first-principles calculations, Sb 2 Te 3 , Bi 2 Te 3 , Topological insulators (TIs) provide intriguing prospects for the future of spintronics due to their large spin-orbit coupling and dissipationless, counterpropagating conduction channels in the surface state. The combination of topological properties and magnetic order can lead to new quantum states including the quantum anomalous Hall effect th...

show abstract

Dirac gap opening and Dirac-fermion-mediated magnetic coupling in antiferromagnetic Gd-doped topological insulators and their manipulation by synchrotron radiation

Cited by 28 publications

References 57 publications

Rational Design Principles of the Quantum Anomalous Hall Effect in Superlatticelike Magnetic Topological Insulators

Rational Design Principles of the Quantum Anomalous Hall Effect in Superlatticelike Magnetic Topological Insulators

Механизм открытия щели в точке Дирака в электронном спектре Gd-допированного топологического изолятора

Magnetic Topological Insulator Heterostructures: A Review

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