Cyclotron resonance of polarons in AgBr at high microwave fields

A cyclotron resonance experiment on polarons in pure AgBr has been extended to the microwave field of 3 kV cm^?1 by using a pulsed magnetron at 35 GHz at lattice temperatures of 4.2 and 17 K in magnetic fields up to 58 kOe. It was established that the ground state polaron mass is m¹_p(0)=(0.287±0.003)m_e. From microwave field dependences of the peak position and the width of resonance lines, it was established that the electron polaron follows the streaming motion repetitively emitting LO-phonons in the microwave field region above 80 V cm^?1. Further, it was also suggested that, when streaming, the polaron has an enhanced effective mass of (0.353±0.006)m_e rather than the ground state mass m¹_p(0).     

Cyclotron resonance of electrons and holes in TlBr

Cyclotron resonance measurements on TlBr with circularly polarized waves at 34 GHz show the presence of an electron resonance at (0.52 ± 0.03)m_o and a hole resonance at (0.70 ± 0.03)m_o. Mobilities of both electrons and holes are determined in the temperature range 6.5°K to 14°K.     

Cyclotron resonance of holes in silicon in quantizing magnetic fields

The cyclotron resonance spectra of holes in bulk silicon in quantizing magnetic fields are investigated in the low-temperature range. The data obtained agree well with the results of the numerical calculation performed earlier by Owner-Petersen and Samuelsen for effective cyclotron masses m*/m₀ and matrix elements M upon transitions between different Landau levels of holes in silicon with a magnetic-field orientation H ∥ [001].     

Cyclotron resonance of electrons and holes in electric surface subbands of tellurium

We present first measurements of the submillimeter-cyclotron resonance of electrons and holes in electric surface subbands of tellurium. From the resonance in the inversion layer we have obtained for the magnetic field paralled to the trigonal axis, the cyclotron mass of the surface electron m_ce = (0.117 ± 0.002)m₀. The resonance of the accumulation layer splits and suggests the contribution of different nonparabolic subbands.     

Cyclotron resonance in quasi-two-dimensional conductors

A theoretical analysis is made of the resonant absorption of RF electromagnetic wave energy in layered conductors having a quasi-two-dimensional electron energy spectrum. An analysis is made of the influence of possible drift of carriers into the conductor and their Fermi-liquid interaction on the position of the cyclotron resonance lines. A reason is given for the substantial difference between the cyclotron effective masses determined from the temperature dependence of the amplitude of the Shubnikov-de Haas oscillations and from measurements of the cyclotron resonance frequencies in [5–7]. It is shown that by means of an experimental investigation of cyclotron resonance in a magnetic field parallel to the layers, it is possible to find the carrier velocity distribution at the Fermi surface in layered organic conductors.     

Cyclotron resonance in bilayer graphene

We present the first measurements of cyclotron resonance of electrons and holes in bilayer graphene. In magnetic fields up to B=18 T, we observe four distinct intraband transitions in both the conduction and valence bands. The transition energies are roughly linear in B between the lowest Landau levels, whereas they follow square root[B] for the higher transitions. This highly unusual behavior represents a change from a parabolic to a linear energy dispersion. The density of states derived from our data generally agrees with the existing lowest order tight binding calculation for bilayer graphene. However, in comparing data to theory, a single set of fitting parameters fails to describe the experimental results.     

Cyclotron resonance in a two-dimensional semimetal

Cyclotron resonance in a two-dimensional semimetal has been studied theoretically, keeping in mind recent experiments reported in Z. D. Kvon, S. N. Pamilov, S. D. Ganichev, et al., in Proceedings of the 14th International Conference on Narrow Gap Semiconductors and Systems (Sendai, Japan, 2009). Since the size of the sample is finite, the exciting microwave inhomogeneous and there is a plasma shift of resonance frequency. There are two magnetoplasmon branches in a two-component system, which undergo pseudocrossing under the found criterion. Resonance frequencies and intensities of absorption peaks have been found. The latter are complicated functions of the electron and hole densities.     

Cyclotron resonance in asymmetric double quantum wells

Far-infrared magnetotransmission measurements in magnetic fields are carried out on asymmetric coupled double wells. We observe a splitting in the cyclotron resonance (CR) line for a wide range of intermediate magnetic fields and only one line at high magnetic fields. Two peaks observed in the CR spectra correspond to transitions between Landau levels in individual wells. We propose that phase transition between weak and strong coupling regimes may be responsible for the features. The characteristics of the transition are studied via an analysis of CR masses, CR splitting and line widths as a function of the magnetic field.     

Cyclotron resonance under uniaxial stress in tellurium

We present cyclotron resonance measurements in pure Te for B 6 c in the Voigt configuration under uniaxial stress p 6 c up to 2·10⁹ dyn/cm². The maximum shift of the resonance line of about 10 per cent is interpreted as change of the band structure. Shift and line shape are in good agreement with theoretical predictions.     

Cyclotron resonance of electrons in localized surface states

The distribution of dipole strength is calculated for a system of electrons moving in a twodimensional surface subband in the presence of a magnetic field. At low densities, where an appreciable part of the electrons occupy localized states the cyclotron resonance exhibits a characteristic field and density dependent structure. The observed drop of the apparent cyclotron mass in Si (100) surfaces is described. The effective activation energy is calculated. From the mobility data in the activated conduction regime it is concluded that only about 20% of the localized states have a localization range of the order of 100 Å or less.     

Cyclotron resonance of polarons in ternary mixed crystals

Rayleigh-Schr?dinger perturbation theory and an improved Wigner-Brillouin perturbation theory has been used to study the cyclotron resonance of the polarons in ternary mixed crystals in the zero-temperature limit. The interaction between an electron and two branches of longitudinal optical phonon modes is taken into account in the framework of the random-element-isodisplacement model. The numerical results for several ternary mixed crystals show that the polaronic cyclotron energy and mass split successively twice related to the higher and lower branches of longitudinal optical phonon modes of ternary mixed crystals. A non-linear dependence of the polaronic cyclotron energy and mass on the composition x is found. Received 19 March 2002 / Received in final form 21 March 2003 Published online 20 June 2003 RID="a" ID="a"e-mail: xxliang@imu.edu.cn     

Cyclotron resonance and screening effects in GaAs-GaAlAs heterojunctions

Cyclotron resonance absorption has been studied in several high quality GaAs-GaAlAs heterojunctions. The dependence of the effective mass upon frequency, electron concentration and temperature has been measured and gives a nonparabolicity that is some 20% smaller than that measured in bulk GaAs. This is contrary to simple theory which predicts an enhanced polaron contribution in two-dimensional systems, and we attribute this difference to strong screening of the electron-phonon interaction. The presence of a small magnetic field component parallel to the interface introduces a coupling at energies corresponding to the electric subband separations. These couplings have been studied as a function of electron concentration and the results interpreted in terms of changes in the depletion charge in the GaAs layer.     

Cyclotron resonance of Dirac ferions in HgTe quantum wells

Cyclotron resonance of single-valley two-dimensional Dirac fermions in HgTe-based quantum wells has been experimentally investigated. The thickness of the wells is close to the critical value corresponding to the transition from the direct energy spectrum to the inverted spectrum. Under terahertz laser irradiation, transitions between the ground and first Landau levels, as well as between the first and second Landau levels, have been observed. Low magnetic fields corresponding to the cyclotron resonance, as well as the strong dependence of the position of the resonance on the electron density, indicate the Dirac character of the spectrum in these quantum wells. It has been shown that disorder plays an important role in the formation of the spectrum of two-dimensional Dirac fermions.     

Cyclotron resonance of two-dimensional electrons forming wigner crystal

The cyclotron resonance peak shape is analysed for two-dimensional electrons interacting with surface vibrations of a medium. Explicit expressions for the broadening and shift of the peak are obtained at low and high electron densities.