Direct measurements of the spin and the cyclotron gaps in a 2D electron system in silicon

Using magnetocapacitance data in tilted magnetic fields, we directly determine the chemical potential jump in a strongly correlated two-dimensional electron system in silicon when the filling factor traverses the spin and the cyclotron gaps. The data yield an effective g factor that is close to its value in bulk silicon and does not depend on the filling factor. The cyclotron splitting corresponds to the effective mass that is strongly enhanced at low electron densities.     

Direct measurements of fractional quantum Hall effect gaps

We measure the chemical potential jump across the fractional gap in the low-temperature limit in the two-dimensional electron system of GaAs/AlGaAs single heterojunctions. In the fully spin-polarized regime, the gap for filling factor nu=1/3 increases linearly with the magnetic field and is coincident with that for nu=2/3, reflecting the electron-hole symmetry in the spin-split Landau level. In low magnetic fields, at the ground-state spin transition for nu=2/3, a correlated behavior of the nu=1/3 and nu=2/3 gaps is observed.     

Light Higgs boson in the two-doublet model featuring explicit <Emphasis Type="Italic">CP</Emphasis> violation

The most general form of an effective two-doublet Higgs potential whose parameters are complex-valued and whose CP invariance is violated explicitly in the minimal supersymmetric model caused by Higgs boson interaction with third-generation squarks is considered. Higgs boson states are obtained and their masses are calculated, along with the decay widths of the lightest Higgs boson and the cross section for its production, in the case of substantial mixing between the CP-even states h and H and the CP-odd state A.     

Scaling analysis of the magnetic field-tuned quantum transition in superconducting amorphous In-O films

We studied the magnetic field-tuned superconductor-insulator transition (SIT) in amorphous In-O films with different oxygen contents and, hence, different electron densities. Whereas the two-dimensional scaling behavior was confirmed for the states of the film near the zero-field SIT, the SIT scenario changed for the deeper states in the superconducting phase; in addition to the scaling function describing the conductivity of the fluctuation-induced Cooper pairs, the temperature-dependent contribution to the film resistance emerged. This contribution can originate from the conductivity of normal electrons.     

Lateral tunneling through the controlled barrier between edge channels in a two-dimensional electron system

A study is made of the lateral tunneling between edge channels at the depletion-induced edges of a gated two-dimensional electron system, through a gate-voltage-controlled barrier arising when the donor layer of the heterostructure is partly removed along a fine strip by means of an atomic force microscope. For a sufficiently high barrier the typical current-voltage characteristic is found to be strongly asymmetric, having, in addition to the positive tunneling branch, a negative branch that corresponds to the current overflowing the barrier. It is established that the barrier height depends linearly on both the gate voltage and the magnetic field, and the data are described in terms of electron tunneling between the outermost edge channels. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 561–566 (25 April 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Zero-bias tunneling anomaly in a two-dimensional electron system with disorder

The temperature dependence of a zero-bias anomaly in the tunneling conductance of an Al/δ-GaAs tunneling structure with a two-dimensional electron density in the δ-layer of 3.5 × 10¹² cm^?2 has been investigated. It has been shown that the respective drop Δρ(?, T) in the tunneling density of states ρ near the Fermi level E _F of the two-dimensional electron system depends logarithmically on the energy ? within the range of 2.7kT < |?| < ?/τ, where ? is measured with respect to E _F and τ is the momentum relaxation time of two-dimensional electrons. It has been found that the drop depth Δρ(0, T)/ρ is also proportional to ln(kT/?₀) in the temperature range T = 0.1–20 K and saturates below 0.1 K.     

Coherent radiation under conditions of the propagation of heavy charged particles through the dielectric in an external electric field

The process of electromagnetic radiation arising during the propagation of heavy charged particles through a dielectric layer situated in an external electric field is investigated. This radiation is due to the degradation of polarization medium induced by the field. The local maximum within the centimeter frequency range of the energy spectrum is analyzed under varying external parameters of the model. Conditions that might allow for the intensity of the radiation to be comparable to the transition radiation are found.     

Formation of associates of solvated cations in salt solutions in polar dielectric liquids

Experimental results are presented on excitation of oscillations of polarization charges of solvated ions in an aqueous solution of a mixture of cerium and lead nitrates under an external asymmetric electric field and the directed motion of solvated cerium and lead cations, caused by this process. The applicability of the approximation of the existence of a self-consistent electric field in the solution volume to explain the observed frequency ranges of the manifestation of the effect of electroinduced selective drift of solvated cations is demonstrated. The results of a theoretical analysis of the possibility of forming associates from solvated ions are presented.     

Collective effects in the transport properties of two-dimensional electron systems

The results of the experimental study of the nontraditional manifestations of collective effects in the transport properties of two-dimensional electron systems are reported.