Abstract
Quantum point contacts (QPC) are a primary component in mesoscopic physics and have come to serve various purposes in modern quantum devices. However, fabricating a QPC that operates robustly under extreme conditions, such as high bias or magnetic fields, still remains an important challenge. As a solution, we have analyzed the trench-gated QPC (t-QPC) that has a central gate in addition to the split-gate structure used in conventional QPCs (c-QPC). From simulation and modelling, we predicted that the t-QPC has larger and more even subband spacings over a wider range of transmission when compared to the c-QPC. After an experimental verification, the two QPCs were investigated in the quantum Hall regimes as well. At high fields, the maximally available conductance was achievable in the t-QPC due to the local carrier density modulation by the trench gate. Furthermore, the t-QPC presented less anomalies in its DC bias dependence, indicating a possible suppression of impurity effects.
Highlights
Quantum point contacts (QPC) are a primary component in mesoscopic physics and have come to serve various purposes in modern quantum devices
QPCs typically suffer from nonideal characteristics under extreme conditions, such as nonlinearities at high biases and transmissions or irregularities under magnetic fields, and the construction of a robust QPC still remains a crucial challenge
The trench-gated QPC (t-QPC) has been used in the past to explore mesoscopic phenomena and unconventional 2DESs18–21, and several studies have sought to characterize the properties of the variant device geometry[22,23,24,25]
Summary
Quantum point contacts (QPC) are a primary component in mesoscopic physics and have come to serve various purposes in modern quantum devices. QPCs typically suffer from nonideal characteristics under extreme conditions, such as nonlinearities at high biases and transmissions or irregularities under magnetic fields, and the construction of a robust QPC still remains a crucial challenge. Previous characterization studies emphasized the role of a trench gate in the enhancement of QPC subband spacings during split gate modulation. We have characterized a t-QPC by modulating the trench gate rather than the split gate and compared it to the performance of a conventional QPC. We emphasize that trench gate modulation maintains a uniform large subband spacing even at higher numbers of conducting channels. The magnetoconductance have been investigated up to high magnetic fields, and the t-QPC was observed to be more robust against complications in the quantum Hall regime
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