  The surface state of a 3D topological insulator (3DTI) is a spin-momentum
locked conductive state, whose large spin hall angle can be used for the
energy-efficient spin orbit torque based switching of an overlying ferromagnet
(FM). Conversely, the gated switching of the magnetization of a separate FM in
or out of the TI surface plane, can turn on and off the TI surface current. The
gate tunability of the TI Dirac cone gap helps reduce its sub-threshold swing.
By exploiting this reciprocal behaviour, we can use two FM/3DTI
heterostructures to design a 1-Transistor 1-magnetic tunnel junction random
access memory unit (1T1MTJ RAM) for an ultra low power Processing-in-Memory
(PiM) architecture. Our calculation involves combining the Fokker-Planck
equation with the Non-equilibrium Green Function (NEGF) based flow of
conduction electrons and Landau-Lifshitz-Gilbert (LLG) based dynamics of
magnetization. Our combined approach allows us to connect device performance
metrics with underlying material parameters, which can guide proposed
experimental and fabrication efforts.
