Circular photogalvanic effect in HgTe/CdHgTe quantum well structures
B. Wittmann, S. N. Danilov, V. V. Bel'kov, S. A. Tarasenko, E. G. Novik, H. Buhmann, C. Brüne, L. W. Molenkamp, Z. D. Kvon, N. N. Mikhailov, S. A. Dvoretsky, N.… 展开作者
B. Wittmann, S. N. Danilov, V. V. Bel'kov, S. A. Tarasenko, E. G. Novik, H. Buhmann, C. Brüne, L. W. Molenkamp, Z. D. Kvon, N. N. Mikhailov, S. A. Dvoretsky, N. Q. Vinh, A. F. G. van der Meer, B. Murdin, S. D. Ganichev
We describe the observation of the circular and linear photogalvanic effects in HgTe/CdHgTe quantum wells. The interband absorption of mid-infrared radiation as well as the intrasubband absorption of terahertz (THz) radiation in the QWs structures is shown to cause a dc electric current due to these effects. The photocurrent magnitude and direction varies with the radiation polarization state and crystallographic orientation of the substrate in a simple way that can be understood from a phenomenological theory. The observed dependences of the photocurrent on the radiation wavelength and temperature are discussed.
We calculate the dispersion of the plasmon-LO modes taking into account the spatial dispersion of the electronic polarizability. It is shown that stimulated emission of the plasmon-LO mode is possible in the frequency range corresponding to the Reststrahlen band of GaAs both in a 6 nm wide HgTe/CdTe QW and in a 5 nm wide HgTe/Cd0.7Hg0.3Te QW grown on the (013) plane. Due to the anisotropy of the dispersion law for the plasmon-LO mode, the [03-1] direction appears to be optimal for generation.
Magnetic field effects on edge and bulk states in topological insulators based on HgTe/CdHgTe quantum wells with strong natural interface inversion asymmetry
We report on observation of an unconventional structure of the quantum Hall effect (QHE) in a $ p$-type HgTe/Cd$_x$Hg$_{1-x}$Te double quantum well (DQW) consisting of two HgTe layers of critical width. The observed QHE is a reentrant function of magnetic field between two $i=2$ states (plateaus at $ρ_{xy}=h/ie^2$) separated by an intermediate $i=1$ state, which looks like some anomalous peak on the extra-long $i=2$ plateau when weakly expressed. The anomalous peak apparently separates two different regimes: a traditional QHE at relatively weak fields for a small density of mobile holes $p_s$ …
We report on the study of magneto-photogalvanic and magnetotransport phenomena in 200 nm partially strained HgTe films. This thickness is slightly larger than the estimated critical thickness of lattice relaxation leaving the film partially relaxed with the value of the energy gap close to zero. We show that illumination of HgTe films with monochromatic terahertz laser radiation results in a giant resonant photocurrent caused by the cyclotron resonance in the surface states. The resonant photocurrent is also detected in the reference fully strained 80 nm HgTe films previously shown to be fully…
The dispersion laws of two-dimensional plasmons in narrow-gap HgTe/CdHgTe quantum wells are calculated taking into account the spatial dispersion of the electron susceptibility. At the energy scale of the band gap the dependence of plasmon frequencies on the wave vector is shown to be close to linear that changes significantly the critical concentration of noneqilibrium electron-hole gas corresponding to "switching-on" the carrier recombination with plasmon emission. The recombination rates with the plasmon emission have been calculated.
Enhanced circular photogalvanic effect in HgTe quantum wells in the heavily inverted regime
由于HgTe基量子阱具有很强的自旋-轨道相互作用（SOI），因此表现出非常丰富的自旋相关性质。但由于窄禁带能带结构的强带间耦合，对它们的完整描述超出了简单的抛物线能带模型和传统的Rashba和Dresselhaus SOI项。本文基于密度矩阵的八带$\mathbf{k}\cdot\mathbf{p}$模型，建立了计算$_{0.3}$ Cd $_{0.7}$ Te/HgTe/$_{0.3}$ Cd $_{0.7}$ Te量子阱（HgTe QWs）中圆形光电流效应的理论方法.我们的方法考虑了HgTe量子阱的特殊能带结构和SOI，因此可以用来计算具有非抛物、类Dirac和反向色散的HgTe量子阱中的CPGE电流.本文还探讨了CPGE的微观成因以及结构反转不对称性（SIA）和体反转不对称性（BIA）的相互作用。此外，将该方法推广到线偏振光垂直入射碲化汞量子阱中的纯自旋电流的研究。我们的计算结果支持了以下发现：（i）在反相区，重反HgTe量子阱的能量色散会发生强烈的畸变，导致在一定能谱范围内CPGE的显著增强。(ii)SIA和BIA的相互作用可以导致CPGE电流各向异性地依赖于斜入射光的方位角。(iii)[110]线偏振光产生的PSC $j_{y'}^{x'}$（$x'\parallel[110]$和$y'\parallel[\bar{1}10]$）随HgTe量子阱由正相转变为反相而改变符号…
We report on transport and capacitance spectroscopy study of two kinds of quantum wells, namely Cd$_{0.02}$Hg$_{0.98}$Te and Cd$_{0.06}$Hg$_{0.94}$Te with the thicknesses of 7.4 and 11.5 nm, accordingly. The fraction of Cd was chosen in a way that the both quantum wells are expected to have gapless band structure typical for a Dirac fermions system. We have established that the first quantum well exhibits a massless Dirac fermions system with a quality slightly better then in conventional HgTe quantum wells of critical thickness. Second quantum well exhibits a high-quality two-dimensional topo…
We develop a microscopic theory of the fine structure of Dirac states in $(0lh)$-grown HgTe/CdHgTe quantum wells (QWs), where $l$ and $h$ are the Miller indices. It is shown that bulk, interface, and structure inversion asymmetry causes the anticrossing of levels even at zero in-plane wave vector and lifts the Dirac state degeneracy. In the QWs of critical thickness, the two-fold degenerate Dirac cone gets split into non-degenerate Weyl cones. The splitting and the Weyl point positions dramatically depend on the QW crystallographic orientation. We calculate the splitting parameters related to …
We propose a minimal effective two-dimensional Hamiltonian for HgTe/CdHgTe quantum wells (QWs) describing the side maxima of the first valence subband. By using the Hamiltonian, we explore the picture of helical edge states in tensile and compressively strained HgTe QWs. We show that both dispersion and probability density of the edge states can differ significantly from those predicted by the Bernevig-Hughes-Zhang (BHZ) model. Our results pave the way towards further theoretical investigations of HgTe-based quantum spin Hall insulators with direct and indirect band gaps beyond the BHZ model.
Magnetophotogalvanic Effects Driven by Terahertz Radiation in CdHgTe Crystals with Kane Fermions
University of Regensburg（雷根斯堡大学）；Ioffe Institute（约费研究所）；Rzhanov Institute of Semiconductor Physics（兹哈诺夫半导体物理研究所）；Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier（夏尔·库隆实验室（L2C），CNRS-蒙彼利埃大学联合研究单位5221）
We report on a strong nonlinear behavior of the photogalvanics and photoconductivity under excitation of HgTe quantum wells (QWs) by intense terahertz (THz) radiation. The increasing radiation intensity causes an inversion of the sign of the photocurrent and transition to its superlinear dependence on the intensity. The photoconductivity also shows a superlinear raise with the intensity. We show that the observed photoresponse nonlinearities are caused by the band-to-band \emph{light} impact ionization under conditions of a photon energy less than the forbidden gap. The signature of this kind …
