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教職演講

Quantum electronics in multiplexed devices and spintronic systems

演講者 : Dr. Luke Smith(路克史密斯) (Assistant Research Professor) (QFort, NCKU)
演講時間 : 2022 / 01 / 10 11:10
理學教學新大樓物理系 5F 36567會議室
My talk will cover different aspects of quantum device research for future electronics, including multiplexing schemes for high-throughput measurement, the development of scalable high-quality 2D material systems, and semiconducting spintronic devices. I will give an overview of my multiplexing research, from quantum point contacts fabricated within a two-dimensional electron gas of a semiconductor high-electron mobility transistor, to the integration of arrays of arbitrary 2D nanomaterials and semiconductor nanowires. I will show how multiplexing drives device development by discovering unique devices with unusual properties. Identifying the underlying device conditions leading to their behavior then allows the reverse engineering of reproducible structures. I will show an example discovery, in which graphene grown by chemical vapor deposition—where device quality is typically limited by the fabrication processes required—is shown to host a magnetic-field driven energy gap at charge neutrality, leading to diverging resistance, which is the signature of samples of very high quality. Transitions between quantum tunneling regimes in non-equilibrium transport point to the existence of a high quality region in a narrow constriction where edge disorder is minimized. This suggests the scalable methods used in fabricating this device make it possible to create high quality devices from 2D material for investigating exotic phenomena, using only conventional fabrication techniques.
Spintronics in semiconductor devices is another scheme with potential for next-generation computing, and incorporating additional spin phenomena such as the Kondo effect may open new possibilities for control. I will show electrical control of the Kondo effect in a semiconductor nanostructure, defined using quantum point contacts with spin orbit coupling. The Kondo effect manifests as a peak in conductance in non-equilibrium transport measurements, with a maximum at equilibrium. By coupling the Kondo effect to electron reservoirs with tunable spin-orbit interactions, the conductance peak can be split into two peaks at finite source-drain bias and controlled by only electrical methods.