Strained Topological Insulator Spin Field Effect Transistor

Spin Field Effect transistors have driven decades of research as it is one of the most remarkable spin-based devices. The transistor action in a Spin-FET is realized by controlling the spin-orbit interaction in the channel of the Spin-FET that is placed in between two ferromagnetic contacts with the application of electric field. The electric field causes spin-precession of the current carriers injected into the channel via the source contact and depending on the spin polarization of the drain contact, the carriers can either flow unimpeded or can be barred from flowing which modulates the channel current. In this work, we are introducing a spin field effect transistor that uses a three-dimensional topological insulator (3D-TI) as channel. The 3D-TI is placed on top of a poled piezoelectric film and the energy-dispersion relation and consequently the Dirac velocity of the conducting surface states of the 3D-TI can be controlled by strain that is generated when a voltage is applied to the piezoelectric film. This in causes the rotation of the spins of the injected carriers and hence modulates the channel conductance thereby establishing transistor action. This device is termed as a strained-topological-insulator-spin-field-effect-transistor, or STI-SPINFET. Its conductance on/off ratio is not suitable for it to function as a switch, but it shows oscillatory behavior which can make it applicable as an extremely energy-efficient stand-alone single-transistor frequency multiplier.