Abstract
The subthreshold swing is the critical parameter determining the operation of a transistor in low-power applications such as switches. It determines the fraction of dissipation due to the gate capacitance used for turning the device on and off, and in a conventional transistor it is limited by Boltzmann's tyranny to kBT ln(10)/q. Here, we demonstrate that the subthreshold swing of a topological transistor in which conduction is enabled by a topological phase transition via electric field switching, can be sizably reduced in a noninteracting system by modulating the Rashba spin-orbit interaction. By developing a theoretical framework for quantum spin Hall materials with honeycomb lattices, we show that the Rashba interaction can reduce the subthreshold swing by more than 25% compared to Boltzmann's limit in currently available materials but without any fundamental lower bound, a discovery that can guide future material design and steer the engineering of topological quantum devices.
Highlights
A large fraction of power dissipation in the low-energy operation of a conventional semiconductor transistor occurs due to irreversible charging and discharging of the gate capacitor to turn conduction on and off
FET based on Semenoff type [33] topologically trivial insulating system where ∆so = 0, the absolute trivial band gap opened by the gate electric field remains insensitive to the Rashba spin-orbit interaction (SOI) which is to be contrasted with a Topological Quantum Field Effect transistor (TQFET) based on QSH materials
We have analysed the working of TQFET, employing the energy-zero edge state of QSH honeycomb nanoribbons, based on the conductance which is quantized, topologically protected, and indebted to the intrinsic microscopic quantum phenomena such as SOI and band topology
Summary
A large fraction of power dissipation in the low-energy operation of a conventional semiconductor transistor occurs due to irreversible charging and discharging of the gate capacitor to turn conduction on and off. The impact of topological quantum field effect on the trivial/nontrivial band gaps, critical value of electric field for ON/OFF switching, and reduced sub-threshold swing S∗ of the TQFET can be simulated in terms of atomic SOI, lattice parameters, and Slater-Koster inter-orbital hopping parameters as EG = 2∆so − edzEz
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