Giant Magneto-Optical Faraday Effect in HgTe Thin Films in the Terahertz Spectral Range

Shuvaev, A.; Astakhov, G. V.; Pimenov, A.; Brüne, C.; Buhmann, H.; Molenkamp, L. W.

doi:10.1103/physrevlett.106.107404

Cited by 119 publications

(94 citation statements)

References 11 publications

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“…With appropriate modifications our findings can be extended to HgTe quantum wells which also support single-valley Dirac fermions [25][26][27][28][29] and show a pronounced Faraday effect. 30 …”

Section: Discussionmentioning

confidence: 99%

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

2011

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The surface quantum Hall state, magneto-electric phenomena and their connection to axion electrodynamics have been studied intensively for topological insulators. One of the obstacles for observing such effects comes from nonzero conductivity of the bulk. To overcome this obstacle we propose to use an external magnetic field to suppress the conductivity of the bulk carriers. The magnetic field dependence of galvanomagnetic and electromagnetic responses of the whole system shows anomalies due to broken time-reversal symmetry of the surface quantum Hall state, which can be used for its detection. In particular, we find negative linear dc magnetoresistivity and a quadratic field dependence of the Hall angle, shifted rf cyclotron resonance, nonanalytic microwave transmission coefficient and saturation of the Faraday rotation angle with increasing magnetic field or wave frequency.

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Section: Discussionmentioning

confidence: 99%

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

2011

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“…In well-investigated case of graphene [6,7] the states are fourfold degenerate, i.e. γ = 4, as two Dirac cones are present in the Brillouin zone which are both doubly spin-degenerate.Magneto-optics in the terahertz range has been proven to be an effective tool to investigate two-dimensional conducting states in several quantum systems, like graphene [8-10], Bi 2 Se 3 [11][12][13][14], and HgTe [15][16][17][18][19][20][21][22]. Magneto-optical spectroscopy has the advantages of being contact-free and of directly accessing the effective mass m c via the cyclotron resonance Ω c = eB/m c .…”

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confidence: 99%

Universal Faraday Rotation in HgTe Wells with Critical Thickness

et al. 2016

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The universal value of Faraday rotation angle close to the fine structure constant (α ≈ 1/137) is experimentally observed in thin HgTe quantum wells with thickness on the border between trivial insulating and the topologically non-trivial Dirac phases. The quantized value of the Faraday angle remains robust in the broad range of magnetic fields and gate voltages. Dynamic Hall conductivity of the hole-like carriers extracted from the analysis of the transmission data shows theoretically predicted universal value of σxy = e 2 /h consistent with the doubly degenerate Dirac state. On shifting the Fermi level by the gate voltage the effective sign of the charge carriers changes from positive (holes) to negative (electrons). The electron-like part of the dynamic response does not show quantum plateaus and is well described within the classical Drude model. PACS numbers:The strong spin-orbit coupling and an inverted band structure in mercury telluride makes this material to a nearly universal tool to probe novel physical effects with the film thickness being a tuning parameter [1,2]. If the thickness of HgTe wells is below critical, d < d c ≈ 6.3 nm, the sequence of the conduction and valence bands is conventional and a trivial insulating state is realized. For thicker films and in the bulk mercury telluride the inversion of valence and conduction bands leads to topologically non-trivial surface states [3,4]. This state is characterised by the locking of the electron spin and the electron momentum and they are topologically protected against non-magnetic impurity scattering.If the thickness of HgTe well is equal to critical, the gap between valence and conduction bands disappears and a two-dimensional (2D) electron gas is formed with Dirac cone dispersion [1,2]. Close to the center of the Dirac cone the electron spin is not a good quantum number, but has to be replaced by pseudo-spin or helicity [3,5]. Due to the particle-hole symmetry of these states, the quantum Hall effect becomes shifted by a half-integer and takes the form σ xy = γ(n+1/2)e 2 /h. In well-investigated case of graphene [6,7] the states are fourfold degenerate, i.e. γ = 4, as two Dirac cones are present in the Brillouin zone which are both doubly spin-degenerate.Magneto-optics in the terahertz range has been proven to be an effective tool to investigate two-dimensional conducting states in several quantum systems, like graphene [8-10], Bi 2 Se 3 [11][12][13][14], and HgTe [15][16][17][18][19][20][21][22]. Magneto-optical spectroscopy has the advantages of being contact-free and of directly accessing the effective mass m c via the cyclotron resonance Ω c = eB/m c . Here B is the external magnetic field.In the dynamical regime the unusual character of the quantum Hall effect in systems with Dirac cones can be shown [23][24][25][26] to lead to a universal values of the Faraday and Kerr rotation with θ F = α ∼ 1/137 and θ K = π/2, respectively. Such predictions have been recently confirmed experimentally in graphene [9], where the Faraday angle is additio...

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“…To date, THz magneto-optical phenomena have been mostly studied either in conducting materials without magnetic order or in magnetically ordered non-conducting materials. [8][9][10][11][12][13][14][15][16][17][18][19] Moreover, the majority of these works studied the Faraday rotation, while other magneto-optical effects, like magnetization dependent linear birefringence and dichroism, may be equally important for establishing a link between electronic transport properties and THz magneto-optics. Measurements on magnetically ordered and conducting samples were reported in Refs.…”

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Terahertz magneto-optics in the ferromagnetic semiconductor HgCdCr2Se4

Huisman

Mikhaylovskiy

Telegin

et al. 2015

Applied Physics Letters

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The magneto-optical response of the ferromagnetic semiconductor HgCdCr2Se4 at terahertz (THz) frequencies is studied using polarization sensitive THz time-domain spectroscopy. It is shown that the polarization state of broadband terahertz pulses, with a spectrum spanning from 0.2 THz to 2.2 THz, changes as an even function of the magnetization of the medium. Analysing the ellipticity and the rotation of the polarization of the THz radiation, we show that these effects originate from linear birefringence and dichroism, respectively, induced by the magnetic ordering. These effects are rather strong and reach 102 rad/m at an applied field of 1 kG which saturates the magnetization of the sample. Our observation serves as a proof-of-principle showing strong effects of the magnetic order on the response of a medium to electric fields at THz frequencies. These experiments also suggest the feasibility of spin-dependent transport measurements on a sub-picosecond timescale.

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Giant Magneto-Optical Faraday Effect in HgTe Thin Films in the Terahertz Spectral Range

Cited by 119 publications

References 11 publications

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

Universal Faraday Rotation in HgTe Wells with Critical Thickness

Terahertz magneto-optics in the ferromagnetic semiconductor HgCdCr2Se4

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