Voltage-controlled topological-spin switch for ultra-low-energy computation

In this paper, we present the functionality and model the performance of a new spin-based logic device called the voltage-controlled topological-spin switch (vTOPSS). This device stores information in the magnetization of a thin magnetic insulator (MI) layer, which has ultra-fast dynamics and low-energy dissipation due to its small damping factor. To control the magnetization of the MI, a voltage signal is applied to a proximal topological insulator (TI) layer, which has a high charge-to-spin conversion efficiency at room temperature. The information in the MI layer is read using a magnetic tunnel junction (MTJ) voltage divider with sub-100 mV read voltages. Since its input/output state variables are in the voltage domain, the vTOPSS device does not require any transduction circuitry to be integrated with the CMOS technology. Device optimization shows that the vTOPSS device can operate with sub-25 aJ energy dissipation and < 30 nW power in on-state, these values are much lower than those reported in contemporary spin-based devices. Results confirm that the dominant component of energy dissipation is due to the TI leakage, which can be reduced by suppressing the surface and bulk charge conduction in the TI. Unlike CMOS devices, energy dissipation of the VTOPSS device is proportional to its switching delay. To simultaneously achieve low latency and energy dissipation in vTOPSS, a TI material with a large spin Hall conductivity and negligible charge conductivity is preferred. Interconnect burden on the performance of the vTOPSS device is minimal, which opens up the possibility of using highly resistive nanowires as potential interconnects for this technology.