Mesoscopic fluctuation effects in the fractional quantum Hall regime 'Mesofrac'

Información del proyecto

Identificador del acuerdo de subvención: INTAS-94-0668

Proyecto cerrado

Fecha de inicio 1 Marzo 1995

Fecha de finalización 28 Febrero 1997

Financiado con arreglo a

• International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993-

Coste total € 0,00

Aportación de la UE € 40 000,00

Coordinado por

Centre National de la Recherche Scientifique
France

Exploitable results

Mesoscopic fluctuation effects in the fractional quantum hall regime Mesofrac

The project investigated a wide range of mesoscopic phenomena arising in the system of composite fermion moving in the presence of random potential. Among these are the universal conductance fluctuations, mesoscopic photovoltaic effect, mesoscopic thermopower and mesoscopic microwave photoconductivity. All of these effects have been thoroughly studied in electron systems both in weak magnetic fields and in the limit of integer quantum Hall effect and in both cases found to be satisfactorily described in terms of electron wave interference. The formalisation of composite fermions has led to a wide range of experiments aimed at the investigation of both the quasiclassical and quantum interference properties of the new quasiparticles. We have investigated mesoscopic resistance fluctuations in electron microstructures in the vicinity of v=1/2. For the first time the mesoscopic fluctuations have been studied both in the gate voltage and in magnetic field dependencies of Rxx. It is established that the fluctuations in these two types of dependencies have the same average amplitude and temperature dependence. It was experimentally proved the theory predicted by Falko universal relation between two types of fluctuations, according to which the ratio of the correlation magnetic field to the correlation electron density should be equal to the magnetic flux quantum multiplied by the inverse filling factor. As the universal conductance fluctuations are very sensitive to the specific disorder potential, it is possible to use this technique to probe the non homogeneous and random effective magnetic field close to v=1/2. Microwave conductivity experiments, without electrical contacts, were developed and millimetre wave photovoltaic effect were studied in the fractional quantum Hall effect regime (frequency range 27-40 GHz) under high magnetic field. Microcharacterisation of these samples were performed by atomic force microscope and by scanning tunnelling microscope.