Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 28: Focus Session: Topological Insulators (jointly with MA, TT)
HL 28.4: Talk
Tuesday, March 27, 2012, 10:15–10:30, ER 164
Cyclotron resonance of two-dimensional Dirac fermions in HgTe-based quantum well structures — Z.D. Kvon1,2, S.N. Danilov3, D.A. Kozlov1,2, •C. Zoth3, N.N. Mikhailov1, S.A. Dvoretsky1, V.V. Bel’kov4, and S.D. Ganichev3 — 1Institute of Semiconductor Physics, Novosibirsk, Russia — 2Novosibirsk State University, Novosibirsk, Russia — 3Terahertz Center, Rgensburg, Germany — 4Ioffe Institute, St. Petersburg, Russia
We report on the observation and investigation of cyclotron resonance (CR) of one-valley two-dimensional Dirac fermions in HgTe-based quantum well (QW) structures [1]. Terahertz photoconductivity was measured in (013)-grown QWs with widths of 6.4 and 6.6 nm, which are close to the critical thickness, when the band structure changes from normal to inverted. We show that these QWs are characterized by a linear energy dispersion and, consequently, by nonequidistant Landau levels. Our experiments show a shift by a factor of three of resonance position to smaller magnetic fields in comparison to larger QW widths having a parabolic energy spectrum. Moreover, our data demonstrates that the CR position changes by a factor of three upon variation of carrier density. This observation provides a further proof for nonequidistant Landau levels in our samples. The role of fluctuations of structure parameters, such as QW thickness and magnitude of impurity potential is discussed.
[1] Z.D. Kvon, S.N. Danilov, D.A. Kozlov et al., Pis’ma ZhETF 94, 895 (2011) (JETP Lett. in print)