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Charge noise analysis of metal oxide semiconductor dual-gate Si/SiGe quantum point contacts
摘要： The frequency dependence of conductance noise through a gate-defined quantum point contact fabricated on a Si/SiGe modulation doped wafer is characterized. The 1/f2 noise, which is characteristic of random telegraph noise, is reduced by application of a negative bias on the global top gate to reduce the local gate voltage. Direct leakage from the large global gate voltage also causes random telegraph noise, and therefore, there is a suitable point to operate quantum dot measurement.
关键词： quantum point contacts,global top gate,charge noise,Si/SiGe,random telegraph noise
更新于2025-09-23 15:21:21
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Topologically Nontrivial Valley States in Bilayer Graphene Quantum Point Contacts
摘要： We present measurements of quantized conductance in electrostatically induced quantum point contacts in bilayer graphene. The application of a perpendicular magnetic field leads to an intricate pattern of lifted and restored degeneracies with increasing field: at zero magnetic field the degeneracy of quantized one-dimensional subbands is four, because of a twofold spin and a twofold valley degeneracy. By switching on the magnetic field, the valley degeneracy is lifted. Because of the Berry curvature, states from different valleys split linearly in magnetic field. In the quantum Hall regime fourfold degenerate conductance plateaus reemerge. During the adiabatic transition to the quantum Hall regime, levels from one valley shift by two in quantum number with respect to the other valley, forming an interweaving pattern that can be reproduced by numerical calculations.
关键词： quantum point contacts,quantized conductance,valley degeneracy,bilayer graphene,Berry curvature
更新于2025-09-04 15:30:14