Tuning the Conductance of Dirac Fermions on the Surface of a Topological Insulator

Mondal, Sayan; Sen, Diptiman; Sengupta, K.; Shankar, Ravi

doi:10.1103/physrevlett.104.046403

Cited by 123 publications

(109 citation statements)

References 32 publications

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“…In this work, we are interested in how this local TRS breaking affects the surface states of the TI. However, the local TRS breaking occurs at a length scale which is of the order of the lattice spacing in the antiferromagnet (for e.g., 8.85Å for MnO). Therefore the effects of local TRS breaking occur at very large momenta, which makes it difficult to observe them in experiments.…”

mentioning

confidence: 99%

“…One of the mechanisms by which the surface modes can be disrupted is by breaking the time reversal invariance upon applying a magnetic field. There have been several studies on the effects of a magnetic field either applied directly perpendicular to the surface of a TI 7 or by the proximity effect of a ferromagnet in a heterostructure 8,9 . On the other hand, the effects of an antiferromagnet or a spin density wave on the surface states of the TI is a topic which is much less well-explored.…”

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confidence: 99%

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Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Ghosh²,

et al. 2011

Phys. Rev. B

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We study the effects of spatially localized breakdown of time reversal symmetry on the surface of a topological insulator (TI) due to proximity to a helical spin density wave (HSDW). The HSDW acts like an externally applied one-dimensional periodic(magnetic) potential for the spins on the surface of the TI, rendering the Dirac cone on the TI surface highly anisotropic. The decrease of group velocity along the directionx of the applied spin potential is twice as much as that perpendicular tox. At the Brillouin zone boundaries (BZB) it also gives rise to new semi-Dirac points which have linear dispersion alongx but quadratic dispersion perpendicular tox. The group velocity of electrons at these new semi-Dirac points is also shown to be highly anisotropic. Experiments using TI systems on multiferroic substrates should realize our predictions. We further discuss the effects of other forms of spin density wave on the surface transport property of topological insulator.

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mentioning

confidence: 99%

mentioning

confidence: 99%

Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Ghosh²,

et al. 2011

Phys. Rev. B

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“…Experiments aimed at observing such phenomena have primarily focused on magnetically doped TIs [3][4][5][6][7]. Complementary to the direct magnetic doping of TIs, several theoretical schemes have proposed explorations of a different sample geometry wherein a patterned ferromagnet (FM) is interfaced with a TI [8][9][10][11]. When the magnetic easy axis of the FM overlayer is out-of-plane, a gap opens in the surface states of the vicinal TI and this massive Dirac Hamiltonian should lead to chiral 1D edge states along FM domain walls where the mass changes sign.…”

mentioning

confidence: 99%

Growth and characterization of hybrid insulating ferromagnet-topological insulator heterostructure devices

Kandala

Richardella

Rench

et al. 2013

Applied Physics Letters

106

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We report the integration of the insulating ferromagnet GdN with epitaxial films of the topological insulator Bi2Se3 and present detailed structural, magnetic and transport characterization of the heterostructures. Fabrication of multi-channel Hall bars with bare and GdN-capped sections enable direct comparison of magnetotransport properties. We show that the presence of the magnetic overlayer results in suppression of weak anti-localization at the top surface.Combining three dimensional (3D) topological insulators (TIs) with magnetism is of great current interest because of the unique effects predicted when the time reversal protected topological surface states are modified by symmetry breaking magnetic perturbations [1,2]. Experiments aimed at observing such phenomena have primarily focused on magnetically doped TIs [3][4][5][6][7]. Complementary to the direct magnetic doping of TIs, several theoretical schemes have proposed explorations of a different sample geometry wherein a patterned ferromagnet (FM) is interfaced with a TI [8][9][10][11]. When the magnetic easy axis of the FM overlayer is out-of-plane, a gap opens in the surface states of the vicinal TI and this massive Dirac Hamiltonian should lead to chiral 1D edge states along FM domain walls where the mass changes sign. If the easy axis of the FM lies in-plane, no gap is expected to first order but the moment can be levered outof-plane by an external field, thereby opening or closing a gap. Calculations[12] also show that hexagonal warping effects can lead to a gap even with an in-plane FM. Unlike magnetically doped films [3], such a geometry leaves the bulk band structure unaffected. However, electrical transport experiments require an insulating ferromagnet to ensure current paths that flow solely through the TI. Recent advances in this context have exploited the synthesis of EuS/Bi 2 Se 3 heterostructures [13,14]. In this Letter, we demonstrate an alternative scheme towards such "magnetic gating" proposals by creating hybrid electrical transport devices wherein we interface the insulating FM GdN with a TI (Bi 2 Se 3 ).GdN is an insulating FM that has elicited interest for low temperature spintronic devices, particularly since it can be deposited by reactive sputtering at ambient temperature [15,16]. This is of prime importance in studies of magnetic exchange coupling effects, as it minimizes thermal diffusion of magnetic species. Changing the nitrogen composition allows access to metallic [17] Bi 2 Se 3 thin films were grown by molecular beam epitaxy (MBE) on InP (111)A substrates under typical growth conditions described elsewhere [19]. Following a brief exposure to ambient atmosphere, the films were transferred to a Kurt Lesker CMS-18 system. After an in-situ Ar + surface clean, GdN was deposited by reactive rf sputtering of Gd in an Ar:N 2 environment at ambient temperature. The GdN films were deposited at a rate of ∼ 0.1−0.2Å/sec, with a sputtering power of 4.93 W/cm 2 in a 15% N 2 :Ar gas environment at 5 mTorr pressure with a source to substr...

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“…We find that the approximate formula fits well already for ∆ 0.5 and show in Fig. 3 the comparison between the full integration and the approximation (10).…”

Section: The Out-of-plane Configurationmentioning

confidence: 62%

“…Proximity induced ferromagnetism, where the order parameter can in general be inhomogeneous and timedependent gives rise to phenomena interesting for spintronics and magnetotransport [10][11][12][13] . Due to the spinmomentum locking, electrical current flow leads to a significant contribution to the spin-torque acting on the magnetization dynamics [11][12][13] .…”

Section: Introduction and Modelmentioning

confidence: 99%

Reflectionless transport of surface Dirac fermions on topological insulators with induced ferromagnetic domain walls

Wickles

Belzig

2012

Phys. Rev. B

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The properties of surface Dirac Fermions on a 3D topological insulator in proximity to a magnetic insulator with spatially textured magnetization are considered. We present an exact analytical treatment of the domain wall resistance and the spectrum for an extended generic domain wall with in-plane and out-of-plane magnetizations. In the latter case, we find oscillations in the domain wall resistance as a function of the wall width and for certain widths a complete absence of reflections for all incoming momenta. The surprising occurrence of oscillations and the reflectionless potentials can be related to a supersymmetry of the surface Dirac Hamiltonian combined with the domain wall profile.

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Tuning the Conductance of Dirac Fermions on the Surface of a Topological Insulator

Cited by 123 publications

References 32 publications

Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Anisotropic surface transport in topological insulators in proximity to a helical spin density wave

Growth and characterization of hybrid insulating ferromagnet-topological insulator heterostructure devices

Reflectionless transport of surface Dirac fermions on topological insulators with induced ferromagnetic domain walls

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