Quantum computational speed of a nanowires system with Rashba interaction in the presence of a magnetic field

The present research is designed to examine the dynamic of the quantum computational speed in a nanowire system through the orthogonality speed when three distinct types of magnetic fields are applied: the strong magnetic field, the weak magnetic field, and no magnetic field. Moreover, we investigate the action of the magnetic fields, the spin-orbit coupling, and the system’s initial states on the orthogonality speed. The observed results reveal that a substantial correlation between the intensity of the spin-orbit coupling and the dynamics of the orthogonality speed, where the orthogonality speed decreasing as the spin-orbit coupling increases. Furthermore, the initial states of the nanowire system are critical for regulating the speed of transmuting the information and computations.

Overcoming Boltzmann's Tyranny in a Transistor via the Topological Quantum Field Effect

The sub-threshold swing is the fundamental 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 kBTln(10)/q, or 60 mV per decade. Here, we demonstrate that the sub-threshold 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 non-interacting system by modulating the Rashba spin-orbit interaction via a top-gate electric field. We refer to this as the Topological Quantum Field Effect and to the transistor as a Topological Quantum Field Effect transistor (TQFET). By developing a general theoretical framework for quantum spin Hall materials with honeycomb lattices we explicitly show that the Rashba interaction can reduce the sub-threshold 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 materials design and steer the engineering of topological quantum devices.

Kramers Degeneracy and Spin Inversion in a Lateral Quantum Dot

We show that the axial symmetry of the Bychkov–Rashba interaction can be exploited to produce electron spin-flip in a circular quantum dot, without lifting the time reversal symmetry. In order to elucidate this effect, we consider ballistic electron transmission through a two-dimensional circular billiard coupled to two one-dimensional electrodes. Using the tight-binding approximation, we derive the scattering matrix and the effective Hamiltonian for the considered system. Within this approach, we found the conditions for the optimal realization of this effect in the transport properties of the quantum dot. Numerical analysis of the system, extended to the case of two-dimensional electrodes, confirms our findings. The relatively strong quantization of the quantum dot can make this effect robust against the temperature effects.

Transport properties of fermions with moat spectra

We present here polarization operator of non-relativistic fermions with spin-orbit (SO) Rashba interaction. The spectrum of this fermions is moat type having minimum on a circle. Contrary to Dirac or non-relativistic fermions, Fermi sea here has a geometry of Corbino disk which reflects in a transport properties of excitation’s.