|M.Sc Student||Chekulaev Dimitri|
|Subject||Thermodynamic Chemical Potential of a Two-Dimensional|
|Department||Department of Physics||Supervisor||Professor Michael Reznikov|
|Full Thesis text|
This work is devoted to experimental investigation of the thermodynamic property of a two-dimensional electron gas (2DEG) - the chemical potential dependence on magnetic field. This dependence was extracted using the magnetic field induced recharging of gated 2DEG, the technique previously developed in our group. Its main advantages are high sensitivity (about 1 mBohr per electron) and ability to extract the chemical potential at fixed temperature.
We focused on the normal to the two-dimensional plane magnetic field, especially on the Integer and the Fractional Quantum Hall effect regimes. We point to the problem with the measurements which arises in the minima of the diagonal conductivity sxx of a 2DEG due to the difficulty in recharging the structure, and suggest its solution. The basic idea of the solution is the following: although the chemical potential at sxx minima where the structure cannot be effectively recharged is experimentally inaccessible by our method, one still can tell the chemical potential change through the minima. This possibility was somehow overlooked in magnetocapacitance measurements, which are hindered by similar problem.
We present experimental results for the magnetic field dependence of the chemical potential. We believe that it is the first time the text-book picture of the saw-tooth behavior of the chemical potential on magnetic field was actually measured all the way from zero magnetic field into the Fractional Quantum Hall effect. At integer and pronounced fractional filling factors we compare chemical potential jumps across the gaps in the density of states with quasiparticle activation energy. We found them to be consistent with each other at both integer and fractional filling factors. At fractional filling factors the jumps and the activation gaps are related through the fractional charge of the quasiparticles, therefore our measurements may be viewed as an alternative way to measure the quasiparticle charge.