3 research outputs found
Comparison of the normal state properties of -(BEDT-TTF)Cu(NCS) and its deuterated analogue in high magnetic fields and under high hydrostatic pressures
Details of the Fermi-surface topology of deuterated
-(BEDT-TTF)Cu(NCS) ~have been measured as a function of
pressure, and compared with equivalent measurements of the undeuterated salt.
We find that the superconducting transition temperature is much more
dramatically suppressed by increasing pressure in the deuterated salt. It is
suggested that this is linked to pressure-induced changes in the Fermi-surface
topology, which occur more rapidly in the deuterated salt than in the
undeuterated salt as the pressure is raised. Our data suggest that the negative
isotope effect observed on deuteration is due to small differences in
Fermi-surface topology caused by the isotopic substitution.Comment: 10 pages 3 figure
Studies of crystalline organic molecular materials under extreme conditions
This thesis describes investigations into the properties of -phase BEDT-TTF
charge transfer salts. Charge transfer salts are mainly studied as they are very
useful test beds for fundamental physics due to the tuneability of their proper-
ties and ground states. The effects of temperature and pressure on such systems
have been studied, as these allow access to a wide range of different states and
properties. Transport properties of these systems have been studied to obtain
information about the Fermi surface and effective mass, and the effect of deuter-
ation and also change of pressure media will be discussed. The interaction of
infrared radiation with these systems has also been investigated and simultaneous
pressure and temperature measurements will be presented, something not greatly
studied due to the large technical challenges. The techniques and approaches for
overcoming these are also discussed.
Chapter 1 provides an introduction to the organic materials themselves with
particular emphasis on the actual compounds studied.
Chapter 2 provides the necessary theoretical background for studying organic
charge transfer salts using magnetic quantum oscillations and their infrared re-
ectivity.
Chapter 3 covers the experimental techniques and also discusses some of the
challenges encountered and their solutions to aid others working in this area.
Chapter 4 describes an investigation into the transport properties of -
(ET)2Cu(SCN)2 by studying Shubnikov-de Haas oscillations using both deuter-
ated and normal samples and using two different pressure media, and comparing
it to work done using a third.
Chapter 5 presents an investigation into the pressure dependence of selected
phonon modes in -(ET)2Cu(SCN)2 using infrared radiation on a deuterated sam-
ple.
Chapter 6 presents what is believed to be the first pressure and temperature
dependent infrared study of an organic molecular material. In this case the or-
ganic molecular material is d8--(ET)2Cu[N(CN)2]Br, but the techniques should
be readily transferable to other materials.This thesis is not currently available in ORA