Thermoelectric effects in organic conductors in a strong magnetic field
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TURES AND LOW-DIMENSIONAL SYSTEMS
Thermoelectric Effects in Organic Conductors in a Strong Magnetic Field O. V. Kirichenkoa, V. G. Peschanskiia, and R. A. Hasanb a Verkin
Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, Kharkov, 61103 Ukraine b Bir-Zeit University, Bir-Zeit, West Bank, Autonomy of Palestine e-mail: [email protected]
Abstract—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. PACS numbers: 72.15.Jf DOI: 10.1134/S1063776107070357
A considerable amount of layered conductors have strongly anisotropic metallic conductivity. The electric conductivity in the plane of layers is several orders of magnitude greater than that along the normal n to the layers; this fact is attributed to the quasi-two-dimensional character of the electron energy spectrum. The energy ε(p) of conduction electrons weakly depends on the projection of their momentum pz = n · p onto the normal n to the layers. The Fermi surface (FS) ε(p) = εF of a layered conductor is weakly corrugated along the axis pz and, as a rule, is multisheeted and consists of topologically different elements [1, 2]. According to the energy-band calculations, (BEDT–TTF)2Cu(SCN)2 and (BEDT–TTF)2MHg(SCN)4 organic conductors, where M is either a metal from the groups K, Rb, or Tl, or NH4, have two groups of charge carriers with quasitwo-dimensional and quasi-one-dimensional energy spectra [3]. To understand the electron processes in low-dimensional conductors, one needs detailed information on the energy spectrum of conduction electrons. Electron phenomena in degenerate conductors placed in a strong magnetic field B when the rotation frequency of electrons ωc is much greater than their collision rate 1/τ are very sensitive to the form of the energy spectrum of charge carriers. The investigations of galvanomagnetic phenomena in many layered conductors at low temperatures, when the condition ωcτ 1 is satisfied in practically accessible magnetic fields, have allowed one to determine the topological structure of the FS and some details of the electron spectrum in layered structures [1, 2]. Similar information on charge carriers can be obtained by investigating the thermoelectric resistance in a strong magnetic field. The dependence of the kinetic coefficient that relates the
thermal flux density to the temperature gradient on the magnitude and orientation of a strong magnetic field does not contain any new information on the spectrum compared with that obtainable from the measurement of electric resistance; however, the investigation of thermoelectric phenomena in a strong magneti
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