Temperature-induced spin density wave in a magnetically doped topological insulator Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Se<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>

Lasia, Martha; Brey, L.

doi:10.1103/physrevb.86.045317

Cited by 12 publications

(12 citation statements)

References 40 publications

(54 reference statements)

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“…In the case of a ferromagnetic material near the Curie point an external field causes a strong para-process, resulting in short range ordering of the spins (ferromagnetic ordering) even above the Curie point [49]. Spin density waves have also been claimed to play a role [51]. The magnetic field hinders the phase transition from ferromagnetism to paramagnetism.…”

Section: Temperature Dependencementioning

confidence: 99%

Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals

et al. 2013

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Breaking the time reversal symmetry of a topological insulator, for example by the presence of magnetic ions, is a prerequisite for spinbased electronic applications in the future. In this regard Mn-doped Bi 2 Te 3 is a prototypical example that merits a systematic investigation of its magnetic properties. Unfortunately, Mn doping is challenging in many host materials-resulting in structural or chemical inhomogeneities affecting the magnetic properties. Here, we present a systematic study of the structural, magnetic and magnetotransport properties of Mn-doped Bi 2 Te 3 single crystals using complimentary experimental techniques. These materials exhibit a 6 Authors contributed equally to this work. 7

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Section: Temperature Dependencementioning

confidence: 99%

Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals

et al. 2013

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“…l a positive integer [40]. For a given two-dimensional wave vector k = (k x ,k y ) we diagonalize the Hamiltonian in this basis and we obtain a discrete number of eigenvalues, ε n,k , and the corresponding wave functions,…”

Section: A Electronic Structure Of Topological Insulator Slabsmentioning

confidence: 99%

Optical properties of magnetically doped ultrathin topological insulator slabs

Lasia

Brey

2014

Phys. Rev. B

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Starting from a three-dimensional Hamiltonian, we study the optical properties of ultrathin topological insulator slabs for which the coupling between Dirac fermions on opposite surfaces results in two degenerated gapped hyperbolic bands. The gap is a threshold for the optical absorption and translates in a peak in the imaginary part of the optical conductivity. An exchange field applied perpendicular to the slab splits the degenerated hyperbolic bands and a double step structure comes out in the optical absorption, whereas a double peak structure appears in the imaginary part of the longitudinal optical conductivity. The exchange field breaks time-reversal symmetry and for exchange fields larger than the surfaces coupling gap, the zero frequency Hall conductivity is quantized to e 2 /h. This result implies large values of the Kerr rotation angle and a quantization of the Faraday angle. In ultrathin slabs, the absence of light multiple scattering and bulk conductivity makes the Kerr angle remain rather large in a wide range of frequencies.

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“…We consider the situation where the chemical potential is in a gap of the bulk spectrum, so that free carriers are not present and bulk magnetic ordering is not expected. In the TCI state, however, surface electrons couple the magnetic moments of the substitutional impurities near the surface, and may lead to ferromagnetism [40,41]. We model this by assuming magnetic impurities are present in the system, on one sublattice, near the surface.…”

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confidence: 99%

Surface magnetism in topological crystalline insulators

et al. 2017

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We study topological crystalline insulators doped with magnetic impurities, in which ferromagnetism at the surface lowers the electronic energy by spontaneous breaking of a crystalline symmetry. The number of energetically equivalent groundstates is sensitive to the crystalline symmetry of the surface, as well as the precise density of electrons at the surface. We show that for a SnTe model in the topological state, magnetic states can have two-fold, six-fold symmetry, or eight-fold degenerate minima. We compute spin stiffnesses within the model to demonstrate the stability of ferromagnetic states, and consider their ramifications for thermal disordering. Possible experimental consequences of the surface magnetism are discussed.PACS numbers: 73.20. At,75.70.Rf,75.30.Gw Introduction -Topological crystalline insulators (TCI's) are a class of materials in which the energy bands can host non-trivial topology protected by a crystalline symmetry [1]. These systems support surface states [2] which remain gapless provided the crystal symmetry is unbroken, and are believed to present themselves in (Sn,Pb)Te and related alloys [3][4][5][6][7][8]. Interesting effects may arise when the symmetry protecting a topological band structure is broken. In topological insulators protected by time-reversal symmetry (TRS), magnetic impurities on a surface break this symmetry and form collective states [9][10][11][12][13], which may be understood in terms of a gap opening in the surface spectrum [14].In contrast, TCI's are not protected by TRS, so the loss of this symmetry does not by itself energetically favor ordering of magnetic moments [15,16]. However, a uniform magnetization can undermine one or more relevant crystalline symmetries [17,18]. Indeed, the most common such symmetry is reflection across a mirror plane, of which there can be several. We show below that spontaneous surface magnetization opens a maximal gap when oriented along axes dictated by the bulk symmetries of the system. For a generic surface with a single mirror plane, there are two surface Dirac points at different momenta and energies [19], and in such cases at low temperature this results in a metallic, Ising-like ferromagnet, with the easy axis determined by the chemical potential µ. Importantly, the number of degenerate low-energy directions is enhanced for surfaces with further symmetries. Rotational symmetries in particular yield multiple mirror planes, and connect distinct surface Dirac cones to one another, yielding a multiplicity of easy axis directions. For sufficiently high symmetry, all the surface Dirac points may be related by symmetry operations, resulting in a fully gapped surface spectrum and a large number of groundstate orientations.To illustrate this physics, we present detailed calculations for the (111) surface of (Sn,Pb)Te [8,[20][21][22], using a known model Hamiltonian [3,23]. The (111) surface states are characterized in this system by four surface Dirac points, one at theΓ point and one at each of three Fig. 1(a).] When the system...

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Temperature-induced spin density wave in a magnetically doped topological insulator Bi2Se3

Cited by 12 publications

References 40 publications

Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals

Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals

Optical properties of magnetically doped ultrathin topological insulator slabs

Surface magnetism in topological crystalline insulators

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Temperature-induced spin density wave in a magnetically doped topological insulator Bi2Se3

Cited by 12 publications

References 40 publications

Study of the structural, electric and magnetic properties of Mn-doped Bi2Te3single crystals

Study of the structural, electric and magnetic properties of Mn-doped Bi2Te3single crystals

Optical properties of magnetically doped ultrathin topological insulator slabs

Surface magnetism in topological crystalline insulators

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Product

Resources

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Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals

Study of the structural, electric and magnetic properties of Mn-doped Bi₂Te₃single crystals