The collective electromagnetic wave excitations in layered conductors in an external quantizing magnetic field are studied theoretically. A set of coupled equations for the electric field components and the Greens functions describing collective electromagnetic modes in such a system within the linear-response approach are obtained on the basis of a model of conducting planes embedded into a dielectric matrix. These equations, written in the layer-site representation, provide a basis for studies of the electromagnetic waves in the general case which does not imply either the spatial uniformity across the layers or the homogenity within the conducting planes. The dispersion equations are obtained for the uniform and homogeneous layered conductors, which give a rich structure of collective electromagnetic modes in layered conductors in an external magnetic field. The dispersion and damping of helicons in layered conductors in the regimes of conventional and quantum Hall effects have been studied, both analytically and numerically. Two new modes propagating perpendicular to the magnetic field with frequencies of the order of the plasma frequency have been found.

Індекс рубрикатора НБУВ: В368.313

Рубрики:

Магнітні властивості надпровідників

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

Індекс рубрикатора НБУВ: В368.31

Рубрики:

Надпровідність. Надпровідники

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

The Shubnikov - de Haas (SdH) oscillations of the in-plane conductivity of layered 2D electron gas is calculated. It is shown that layer stacking faults, magnetoimpurity bound states, and electron scattering modulate the SdH oscillations via the specific factors which bear the structural information. At zero temperature the 2D SdH oscillations are strongly nonsinusoidal in shape and related by simple equation to the derivative of the de Haas-van Alphen magnetization oscillations with respect to the magnetic field.

Індекс рубрикатора НБУВ: В368.3

Рубрики:

Фізика низьких температур

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 

We present a theory which is able to explain enhanced magnetic quantum-oscillation amplitudes in the superconducting state of a layered organic metal with incoherent electronic transport across the layers. The incoherence acts through the deformation of the layer-stacking factor which becomes complex and decreases the total scattering rate in the mixed state. This novel mechanism restores the coherence by establishing a long-range order across the layers and can compensate the usual decrease of the Dingle factor below the upper critical magnetic field caused by the intralayer scattering.

The quantum magnetic oscillations (QMO) in the layered and quasi-two-dimensional (2D) conductors deviate from the quasiclassical Lifshitz - Kosevich (LK) theory developed for 3D conventional metals. We discuss deviations related to the broadening of the Landau levels into Landau bands by various mechanisms (layer-stacking, magnetic breakdown, incoherence, disorder, localization etc.). Each mechanism yields a specific factor modulating the QMO amplitudes depending on the density of states and electron velocities within the Landau bands. In contrast to the LK theory, these factors differ for the thermodynamic (de Haas - van Alphen (dHvA)) and kinetic (Shubnikov - de Haas (SdH)) oscillations. We calculated the magnetic breakdown damping factors for the SdH and dHvA oscillations in the 2D conductors and analyzed their difference as well as the analogy between the bandwidth and Weiss oscillations. In case of an isotropic 3D metals the kinetic factors become proportional to the thermodynamic ones as is assumed in the LK theory.