Prof Arzhang Ardavan

Abstract:

An angle-dependent study of the magneto-optical response of the p-wave triplet-paired perovskite superconductor Sr2RuO4\ reveals several new cyclotron resonance effects. We observe an odd-harmonic cyclotron resonance series, probably arising from the gamma Fermi surface, with a fundamental cyclotron mass of 12.6 m(e). In addition, we find several resonance branches which behave in unconventional ways owing to the unusual nature of the band dispersion in this material. The results confirm the complexity of the Sr2RuO4 Fermi surface topology and show that earlier conclusions drawn from millimetre-wave experiments should be reconsidered. (C) 2001 Elsevier Science B.V. All rights reserved.

Abstract:

Single crystals of the quasi-two-dimensional organic type II superconductor, κ-(BEDT-TTF)2Cu(NCS)2, have been studied in magnetic fields of up to 33 T and at temperatures between 0.5 K and 11 K using a compact differential susceptometer. When the magnetic field lies precisely in the quasi-two-dimensional planes of the material, there is strong evidence for a phase transition from the superconducting mixed state into a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, manifested as a change in the rigidity of the vortex system. The behaviour of the transition as a function of temperature is in good agreement with theoretical predictions.

Abstract:

We have investigated the molecular dynamics in the nematic liquid crystal 5CB using the ALC mu SR technique. Our measurements are consistent with a change in the amplitude of director fluctuations at the nematic-isotropic transition and we develop a model to describe this. (C) 2000 Elsevier Science B.V. All rights reserved.