Intersubband scattering inn-GaAs/AlGaAs wide quantum wells

Abstract

Slow magnetooscilations of the conductivity are observed in a 75 nm wide quantum well at heating of the two-dimensional electrons by a high-intensity surface acoustic wave. These magnetooscillations are caused by intersubband elastic scattering between the symmetric and asymmetric subbands formed due to an electrostatic barrier in the center of the quantum well. The tunneling splitting between these subbands as well as the intersubband scattering rate are determined.

Evidence for a quantum dipole liquid state in an organic quasi–two-dimensional material

“…2A ). The difference in frequencies of the two modes is much higher than expected for a structural phase transition, but corresponds to charges redistributed within the (BEDT-TTF) 2 1+ dimer as +0.4 on one molecule, and +0.6 on the other [14,10]; this breaks the inversion symmetry in a (BEDT-TTF) 2 1+ dimer, creating an electric dipole. This result confirms that the ground state of -Hg-Cl is an order of electric dipoles localized on (BEDT-TTF) 2 1+ dimer sites [10], the so-called dipole solid [1].…”

“…2 of the paper are shown in Table S1. Raman scattering spectra of all the discussed compounds show an overlap of electronic and magnetic components, phonons, and lattice vibrations (13), and luminescence which appears at frequencies above 3000 cm -1 (10). Basing on the fits of these different known contributions, their dependence on temperature, polarization, and chemical composition of the samples, we manage to separate these contributions.…”

“…Here we elucidate the properties of the quantum dipole liquid state in the triangular lattice Mott insulator [9,10] -(BEDT-TTF) 2 Hg(SCN) 2 Br ( -Hg-Br ) (T = 80 K [11,12]) by comparing them to those of an isostructural compound -(BEDT-TTF) 2 Hg(SCN) 2 Cl ( -Hg-Cl), which shows signatures of a quantum dipole solid below 30 K [11,10]. We first use Raman molecular vibrational spectroscopy to follow the evolution of the distribution of charge on the lattice of these systems through the metal-insulator transition.…”

“…Because heat capacity is found to not be always sensitive to magnetic phase transitions in these two-dimensional materials [33], further studies such as with nuclear magnetic resonance (NMR) are necessary to identify the magnetic ground state of -Hg-Cl . Paired electron crystal proposed as a ground state of -Hg-Cl [6,10] can be regarded as a variation of a valence bond solid [6,29]. In these terms, the quantum dipole liquid in -Hg-Br can be a realization of a resonant valence bond state [34].…”

Nonlinear AC and DC Conductivities in a Two-Subband n-GaAs/AlAs Heterostructure

“…Such heterostructures also exhibit unusual non-ohmic effects arising with an increase in the electric current flowing across the sample under study at low magnetic fields, at which the intersubband transitions are observed [12][13][14][15]. Despite the long-term history of the research in the field of two-subband electron systems, many aspects of magnetotransport in them are still debatable [16][17][18]. In the presence of two partially filled subbands, the picture of Shubnikovde Haas oscillations (as well as the picture of the integer Hall effect) is quite complicated and requires special investigation.…”