Dr Moon-Sun Nam

Abstract:

A new family of hydrated molecular metals based on the bis(ethylenethio- tetrathiafulvalene) (BET-TTF) donor was developed. A metal stable down to 0.5 K was obtained for the first time from this donor, perhaps due to the absence of disorder in the peripheral sulfur atoms. A hint of superconducting transition in some crystals of the BET-TTF2Br·3H2O salt was observed.

Abstract:

We have performed detailed studies of the angle- and temperature-dependent resistive upper critical fields in the layered organic superconductor κ-(BEDT-TTF)2Cu(NCS)2. With the magnetic field lying in the conducting planes, our measurements show an upper critical field which comfortably exceeds the Pauli-paramagnetic limit in this material. We find no azimuthal angle dependence of the critical field, in spite of recent evidence that this material has gap nodes characteristic of d-wave superconductivity. We propose that the large critical fields may be due to a Fulde-Ferrell-Larkin-Ovchinnikov state which can exist in exactly in-plane fields because of the nature of the Fermi surface of κ-(BEDT-TTF)2Cu(NCS)2. © 1999 IOP Publishing Ltd.

Abstract:

Angle-dependent magnetoresistance oscillations (AMROs) in kappa-(BEDT-TTF)(2)Cu(SCN)(2) have been observed in fields of up to 33 T. AMROs due to both open and closed Fermi surface sections have been measured simultaneously for the first time in an organic metal. This provides information concerning the low temperature Fermi surface and demonstrates the absence of a spin-density wave state in this material.

Abstract:

Using a variant of the Corbino geometry in pulsed magnetic fields of up to 60 T, we have made direct measurements of the Hall potential in (Formula presented) within the quantum Hall regime. This method enables the in-plane components of the resistivity tensor, which are normally very difficult to measure, to be investigated and the nonlinear behavior of the sample’s (Formula presented) characteristics to be studied. It is found that an increasing probability of magnetic breakdown at higher fields leads to a degradation of the quantum Hall effect. © 1999 The American Physical Society.