V. G. Peschansky

Galvanomagnetic phenomena in layered organic conductors (Review)

The experimental research on galvanomagnetic phenomena in layered organic conductors at high magnetic fields is discussed in terms of the theoretical ideas about charge transfer phenomena in conductors with a metallic type of conductivity and a quasi-two-dimensional electron energy spectrum of arbitrary form. Attention is devoted mainly to the problem of recovering the dispersion relation of the conduction electrons in layered organic charge-transfer complexes from experimental studies of their magnetoresistance and quantum oscillation phenomena at low temperatures.

Galvanomagnetic Phenomena in Layered Organic Conductors

The dependence of the resistance and the Hall field in organic metals with the quasi-two-dimensional electron energy spectrum on the magnetic field strength and orientation is analyzed in the strong field limit. The inter-plane resistance is shown to be strongly dependent on the of magnetic field orientation. When the angle θ between the field and the highly conducting plane is zero, the resistance increases linearly in a relatively wide field range. The angle dependence of magnetoresistance at small θ is nonmonotonic: it exhibits a local minimum and then a sharp peak around θ = 0. The Hall constant in strong magnetic field does not depend on the field orientation.

Galvanomagnetic phenomena in organic conductors under topological phase transition

The magnetoresistance of layered organic conductors with a multisheet Fermi surface (FS) is studied theoretically under conditions of the Lifshitz topological transition, where the FS topology may change in response to external effects acting on the conductor, such as pressure or doping with impurity atoms. Using as an example the Fermi surface consisting of a cylinder and two planes, which are slightly corrugated along the projection of the momentum pz=pn along the normal to the layers n, we analyze the magnetic-field dependence of the resistance and the Hall field in a strong external magnetic field H, where the cyclotron frequency ωc of the conduction electrons is much higher than their collision frequency 1/τ. In the immediate vicinity of the topological transition, where the distance between the different sheets of the FS becomes small, an electron can move from one sheet of the FS to another with the probability w due to the magnetic breakdown. In this case, a quadratic increase of the electric resi...

Angular magnetic breakdown oscillations in organic conductorsa)

The dependence of the magnetoresistance oscillations in layered organic conductors with a multisheet Fermi surface on the angle between the magnetic field and the normal to the layers is studied theoretically in the condition of possible magnetic breakdown between different sheets of the Fermi surface. It is shown that the distance between separate cavities of the Fermi surface in momentum space can be determined from the periods of magnetic breakdown oscillations.

Thermomagnetic phenomena in layered conductors

A theoretical study is made of thermomagnetic phenomena in layered conductors in the presence of several groups of charge carriers. The thermopower at high external magnetic field is found as a function of the strength and orientation of the field; experimental study of this field dependence permits investigation of the structure of the energy spectrum of the charge carriers.

Magnetoresistance of organic conductors in the vicinity of a topological phase transition

We analyze the effect of magnetic breakdown on the resistance of layered organic conductors with a multisheet Fermi surface consisting of a cylinder and two slightly corrugated planes along the projection of the momentum onto the normal to the layers. Analytic expressions are derived for the charge carrier distribution function, and the dependences of the interlayer and intralayer conductivities on the magnitude and orientation of the external magnetic field in the immediate vicinity of a topological phase transition are determined when the distance between the different sheets of the Fermi surface is quite small, but the topological structure of the Fermi surface is still intact.

On the propagation of acoustic waves in quasi-two-dimensional conductors in a quantizing magnetic field

The damping of acoustic waves propagating perpendicular to the layers of a quasi-two-dimensional conductor is analyzed for the case of low temperatures, at which the energy quantization of the conduction electrons leads to an oscillatory dependence of the acoustic damping coefficient on the inverse magnetic field. The acoustic damping decrement is found for different orientations of the magnetic field with respect to the layers. It is shown that that a layered conductor is most transparent for an acoustic wave in the case when the magnetic field is perpendicular to the layers.

On the quantum oscillations of the sound attenuation coefficient in layered conductors

The attenuation of a transverse sound wave in a layered conductor with a quasi-two-dimensional dispersion relation of the charge carriers in a quantizing magnetic field is considered. The oscillatory dependence of the sound attenuation coefficient on the inverse magnetic field is analyzed, and the role of Joule losses in the absorption of energy from the sound wave by electrons is ascertained for different orientations of the magnetic field with respect to the plane of the layers.

Thermoelectric Effects in Organic Conductors in a Strong Magnetic Field

The linear response of the electron system of a layered conductor to the temperature gradient in this system in a strong magnetic field is investigated theoretically. Thermoelectric emf is studied as a function of the magnitude and orientation of a strong external magnetic field; the experimental investigation of this function, combined with the study of the electric and thermal resistance, allows one to completely determine the structure of the energy spectrum of charge carriers.

Diamagnetism of layered organic conductors

The temperature dependence of the magnetic susceptibility of layered organic conductors with an arbitrary dispersion law in high magnetic fields is analyzed. It is shown that the quasi-two-dimensional character of the electron energy spectrum of these conductors results in a strong dependence of the diamagnetic contribution to the magnetization on the direction of the applied magnetic field. Experimental investigation of the anisotropy of the magnetic susceptibility makes it possible to study separately the diamagnetic and paramagnetic contributions to the magnetization of layered conductors.