Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 77: Transport in High Magnetic Fields

HL 77.3: Talk

Thursday, March 23, 2017, 15:15–15:30, POT 112

Phase transition induced by impurities in GaAs/AlGaAs single quantum wells — •Eddy P. Rugeramigabo, Lina Bockhorn, and Rolf J. Haug — Institute for Solid State Physics, Leibniz Universität Hannover

We report on a phase transition in two-dimensional electron gases (2DEG) interacting with specific background impurities. These are silicon atoms which have been intentionally incorporated in high quality single GaAs/AlGaAs quantum wells confining the 2DEG. The reference 2DEG, without any additional impurities, has an electron mobility µ_E of 3.2 · 10⁶ cm²/Vs and a 2D electron density n_E of 2.9 · 10¹¹ cm⁻² at low temperature. The incorporated impurities induce a decrease in the sample quality, observed in the lowering of µ_E. However at high magnetic fields they induce a phase transition. The new phase has a metastable equilibrium between 7 T and 13 T (2 < ν > 1). It is characterized by better developed fractional filling factors, e.g. ν = 5/3 and ν = 4/3. The phase transition is shown to be related to nuclear spin polarization.