Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 59: Transport: Poster
TT 59.1: Poster
Mittwoch, 20. März 2024, 15:00–18:00, Poster E
Thermal noise and electrical characterization of mode coupled GaAs/AlGaAs quantum point contacts — •Daniel Nickel1, Birkan Düzel1, Olivio Chiatti1, Sven S. Buchholz1, and Saskia F. Fischer1,2 — 1Novel Materials Group,Humboldt-Universität zu Berlin,10099 Berlin, Germany — 2Center for the Science of Materials Berlin, 12489 Berlin, Germany
Noise measurements are a useful tool to investigate intrinsic system properties in thermodynamic equilibrium. This work investigates the thermal noise and electrical properties of etched single and double quantum point contacts (QPCs) in GaAs/AlGaAs heterostructures at T = 4.2 K. Both QPCs exhibit conductance plateaus indicative of ballistic transport in one dimension. The transconductance as a function of the top and back gate voltages yields information regarding the degeneracies of the 1D subband energies of the double QPC. Crossings are observed when two energy levels are degenerate and anti-crossings are observed when a hybridization of the 1D wave functions occurs. The single QPC subband structure is well-detected in voltage noise measurements in accordance with the expected thermal noise using the Johnson-Nyquist theorem. For the double QPC, additional noise beyond the expected thermal noise is observed. This additional noise occurs in mode coupled states with hybridized wave functions and simultaneous phase-coherent transport, as well as in degenerate states. The increase in voltage fluctuations is discussed in relation to shot noise through the tunnel barrier and correlations between noise sources.
Keywords: Quantum point contacts; thermal noise; mode coupling