Abstract-High-frequency breakdown of the integer QHE in GaAs/AlGaAs heterojunctions

V. Dziom, A. Shuvaev, A. V. Shchepetilnikov, D. MacFarland, G. Strasser, A. Pimenov

https://arxiv.org/abs/1811.08777

The integer quantum Hall effect is a well-studied phenomenon at frequencies below about 100 Hz. The plateaus in high-frequency Hall conductivity were experimentally proven to retain up to 33 GHz, but the behavior at higher frequencies has remained largely unexplored. Using continuous wave THz spectroscopy, the complex Hall conductivity of GaAs/AlGaAs heterojunctions was studied in the range of 69-1100 GHz. Above 100 GHz, the quantum plateaus are strongly smeared out and replaced by weak quantum oscillations in the real part of the conductivity. The amplitude of the oscillations decreases with increasing frequency. Near 1 THz, the Hall conductivity does not reveal any features related to the filling of Landau levels. Similar oscillations are observed in the imaginary part as well, this effect has no analogy at zero frequency. This experimental picture is in disagreement with existing theoretical considerations of the high-frequency quantum Hall effect.

Abstract-Magneto-Optical Modulation of Photonic Spin Hall Effect of Graphene in Terahertz Region

Tingting Tang, Jie Li, Li Luo, Ping Sun, Jianquan Yao,

http://onlinelibrary.wiley.com/doi/10.1002/adom.201701212/full

Magneto-optical (MO) modulation of the photonic spin Hall effect (PSHE) of transmitted light in graphene–substrate system in terahertz region is proposed. The expressions for PSHE shifts of left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) components are derived based on angular spectrum analysis. PSHE shifts and their physical mechanisms are discussed in detail in the presence of different relaxation time and Fermi energy of graphene based on simulation results. The potential applications of MO-modulated PSHE in multichannel switch and barcode encryption are also proposed and discussed. The MO-modulated PSHE in graphene–substrate system provides a new mechanism to realize photonic devices in the terahertz region.

Abstract-Sub-100-ps dynamics of the anomalous Hall effect at terahertz frequencies

T. J. Huisman, R. V. Mikhaylovskiy, Th. Rasing, A. V. Kimel, A. Tsukamoto, B. de Ronde, L. Ma, W. J. Fan, and S. M. Zhou

Phys. Rev. B 95, 094418 – Published 13 March 2017

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.094418

We report about the anomalous Hall effect in $4f3d$ metallic alloys measured using terahertz time-domain spectroscopy. In this way, we succeeded in revealing ultrafast dynamics of the anomalous Hall effect which accompanies the sub-100-ps optically induced magnetization reversal in a GdFeCo alloy. The experiments demonstrate the ability to control currents at terahertz frequencies in spintronic devices magnetically and ultrafast.

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