Prof Arzhang Ardavan

Abstract:

We present a model of a quasi-one-dimensional (Q1D) conductor with weak dispersion in the direction perpendicular to the chains in a magnetic field. Finite-energy electric dipole transitions between the eigenstates of the system constitute Fermi-surface traversal resonance, a Q1D analogue of cyclotron resonance. We extend the model to describe a (TMTSF)(2)X-like material, with dispersion in two directions perpendicular to the chains, and find that for certain orientations of the magnetic field large degeneracies occur between the magnetic-field induced states. These are angles at which maxima are observed experimentally in the d.c. conductivity, and thus we explain one class of angle-dependent magnetoresistance oscillations (AMRO) in terms of zero-energy electric dipole transitions between magnetic-field induced states.

Abstract:

We identify two interplane corrugations in the quasi-one-dimensional Fermi surface sections of the organic superconductor kappa-(BEDT-TTF)(2)Cu(SCN)(2). The warping directions are 17.3 degrees and -19.4 degrees relative to the crystal a* axis.

Abstract:

We present a numerical simulation of angle dependent magnetoresistances oscillations(AMROs) in alpha-(BEDT-TTF)(2)KHg(SCN)(4). The nesting vector of the density wave and the magnetic breakdowngap in the low-temperature, low-magnetic-field state (LTLF) are constrained by simulations of quasi-one-dimensional (Q1D) AMRO. Quasi-two-dimensional (Q2D) AMRO simulations for the high-temperature, high-magnetic-field state (HTHF) allow the precise derivation of an ellipticity of the Q2D Fermi surface. Simulations of the field dependent AMRO demonstrate the gradual evolution of the FS from LTLF to HTHF states toward the kink transition at 23 T.