D. Andres

Orbital effect of a magnetic field on the low-temperature state in the organic metalα−(BEDT−TTF)2KHg(SCN)4

The effect of pressure on the B--T phase diagram of

Orbital quantization in the high-magnetic-field state of a charge-density-wave system

\alpha

B–T–P phase diagram of α-(BEDT-TTF)2KHg(SCN)4

-(BEDT-TTF)

Superconductivity in the charge-density-wave state of the organic metal α-(BEDT-TTF)2KHg(SCN)4

_2

Interplay between the orbital quantization and Pauli effect in a charge-density-wave organic conductor £

KHg(SCN)

Magnetoresistance studies of α-(ET)2KHg(SCN)4 under pressure

_4

Effects of low dimensionality on the classical and quantum parts of the magnetoresistance of layered metals with a coherent interlayer transport

is studied. The measured phase lines can be well described by a recent model of a charge-density wave system with varying nesting conditions. A remarkable increase of the transition temperature with magnetic field is found in a certain pressure and field range. We associate this result with a dramatic enhancement of the orbital effect of magnetic field due to a deterioration of the nesting conditions by pressure. Furthermore, we present data which can be interpreted as a first sign of field-induced charge-density waves.

The phase diagram of a-(BEDT-TTF)2KHg(SCN)4 for magnetic fields almost parallel to the layers

A superposition of the Pauli and orbital coupling of a high magnetic field to charge carriers in a charge-density-wave (CDW) system is proposed to give rise to transitions between subphases with quantized values of the CDW wavevector. By contrast to the purely orbital field-induced densitywave effects which require a strongly imperfect nesting of the Fermi surface, the new transitions can occur even if the Fermi surface is well nested at zero field. We suggest that such transitions are observed in the organic metal �-(BEDT-TTF)2KHg(SCN)4 under a strongly tilted magnetic field.

New electronic phase transitions in α-(BEDT-TTF)2KHg(SCN)4

We present detailed studies of the B-T-P phase diagram of α-(BEDT-TTF) 2 KHg(SCN) 4 by means of magnetic torque and magnetoresistance measurements. The phase diagram for magnetic field oriented almost perpendicular to the highly conducting layers closely resembles that expected for a charge-density-wave (CDW) system with an imperfectly nested Fermi surface. The influence of pressure can be readily understood as deteriorating the nesting conditions and thus enhancing the role of the orbital effect of magnetic field. At field strongly tilted from the normal to the layers, both the torque and magnetoresistance display a number of irreversible features that may be associated with a series of first-order phase transitions. This behaviour is not understood within the existing CDW theories.

Magnetic field-induced charge-density-wave transitions : The role of the orbital and Pauli effects

The superconducting transition in the layered organic compound \alpha-(BEDT-TTF)_2KHg(SCN)_4 has been studied in the two hydrostatic pressure regimes where a charge-density wave is either present or completely suppressed. Within the charge-density-wave state the experimental results reveal a network of weakly coupled superconducting regions. This is especially seen in a strong enhancement of the measured critical field and the corresponding positive curvature of its temperature dependence. Further, it is shown that on lowering the pressure into the density-wave state traces of a superconducting phase already start to appear at a much higher temperature.