08 Fakultät Mathematik und Physik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/9
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Item Open Access Electron correlations in the 2D multilayer organic metal k-(BEDT-TTF)2I3 in magnetic fields(2004) Balthes, Eduard; Schweitzer, Dieter (Prof. Dr.)This work presents quantum oscillation experiments in quasi-twodimensional multilayer organic metals. They show that low integer Landau level filling factors nare present in the two-dimensional organic metal k-(BEDT-TTF)2I3 and give strong indications for the existence of the fractional filling factor n=½ in this material. By this the work shows the presence of electron localisation and electron correlation in a bulk metallic two-dimensional system. These effects are found in the normal conducting state of the organic superconductor k-(BEDT-TTF)2I3. The revolutionary discovery of the integer as well as the fractional quantum Hall effect in two-dimensional semiconducting single-layer systems invoked, i.a., the questions, whether these effects may also be present in other types of conductors and, especially, whether they may also occur in bulk three-dimensional crystals. Strong efforts were made to produce bilayer two-dimensional semiconductors, to control their interlayer coupling as well as electron tunnelling, to increase step by step the number of involved layers with the aim to realise the quantised Hall effects in 'bulk' multilayer and, finally, in 'infinite-layer' systems. Furthermore strong efforts are made in semiconducting two-dimensional systems to realise carrier densities above 1011/cm2 with mobilities exceeding 107cm2/Vs. k-(BEDT-TTF)2I3 is a metallic compound with a very high electron density of 2*1019/cm2 and a very high carrier mobility reaching about 5*108cm2/Vs. From its structural principle this organic material represents a system of 105 coupled metallic multilayers, which can be synthesised in very high purity and can be produced as three-dimensional bulk single crystals. Despite of this, the material shows strongly two-dimensional electronic properties under certain experimental conditions, as found in the frame of this work. In contrast to the characteristic situation in semiconducting two-dimensional systems, where (correlated) electrons move on a single quantised orbit, the strongly correlated carriers in k-(BEDT-TTF)2I3 move on various quantised orbits with even very different filling factors. These are the main conditions under which the above mentioned filling factors are found in k-(BEDT-TTF)2I3. Besides these characteristics, the present two-dimensional organic metal holds a number of further peculiarities, which may represent a challenge for the understanding of possible fractional filling factors and quantum limit in a macroscopic multilayer crystal with two-dimensional electronic properties. In addition, the present work resumes experiments on the influence of low-dimensionality onto the electronic properties of a number of low-dimensional multilayer organic conductors.