Topological charge, spin, and heat transistor

Abstract

Spin pumping consists in the injection of spin currents into a nonmagnetic material due to the precession of an adjacent ferromagnet. In addition to the pumping of spin the precession always leads to pumping of heat, but in the presence of spin-orbital entanglement it also leads to a charge current. We investigate the pumping of charge, spin, and heat in a device where a superconductor and a quantum spin Hall insulator are in proximity contact with a ferromagnetic insulator. We show that the device supports two robust operation regimes arising from topological effects. In one regime, the pumped charge, spin, and heat are quantized and related to each other due to a topological winding number of the reflection coefficient in the scattering matrix formalism, translating to a Chern number in the case of Hamiltonian formalism. In the second regime, a Majorana zero mode switches off the pumping of currents owing to the topologically protected perfect Andreev reflection. We show that the interplay of these two topological effects can be utilized so that the device operates as a robust charge, spin, and heat transistor.

Compact Model of a Topological Transistor

“…Using the deduced closed form equation, we build a Verilog-A-based compact model. Our model can perfectly capture the proposed transistor behavior of the two topological regimes reported in [13]. Our model will enable the device and circuit-level exploration of the device.…”

“…We calibrate our model with the geometric and material parameters corresponding to the QSHI-FI-SC structure reported in [13] (Table I). Using equation ( 8), we build a circuit-compatible Verilog-A-based compact model.…”

“…Becerra et. al. has recently proposed such a device where a quantum spin Hall insulator (QSHI) adjacent to a ferromagnetic insulator (FI) and a superconductor (SC) can harbor Majorana zero mode in the FI-SC junction [13]. This Majorana fermion (MF) enables topologically protected perfect Andreev reflection (AR) [14].…”

A three-terminal magnetic thermal transistor

“…Electrical transistors revolutionized society and have formed the backbone of modern computing and power transmission. Thermal researchers have proposed that thermal transistors could be used in precision thermal management 25 , advanced thermal sensing and integrated control 26 , and passive thermal logic/computation in harsh climates with no available electrical power 4,27,28 .Previous researchers have computationally investigated threeterminal thermal transistors using mechanisms based on thermal radiation 25,26,[29][30][31][32][33][34] , nonlinear phonon conduction in nanoscale systems [35][36][37][38][39][40] , nanoscale confined fluids 41,42 , quantum electronic systems [43][44][45][46][47][48][49][50] , and superconducting devices 51,52 . These proposed mechanisms all involve the concept of a negative differential thermal resistance (NDTR) 35,39 ; using the terminology of a FET, NDTR refers to the regime in which increasing the gate temperature increases the heat flow from the source into the transistor at a fixed source temperature and drain temperature.…”

“…Previous researchers have computationally investigated threeterminal thermal transistors using mechanisms based on thermal radiation 25,26,[29][30][31][32][33][34] , nonlinear phonon conduction in nanoscale systems [35][36][37][38][39][40] , nanoscale confined fluids 41,42 , quantum electronic systems [43][44][45][46][47][48][49][50] , and superconducting devices 51,52 . These proposed mechanisms all involve the concept of a negative differential thermal resistance (NDTR) 35,39 ; using the terminology of a FET, NDTR refers to the regime in which increasing the gate temperature increases the heat flow from the source into the transistor at a fixed source temperature and drain temperature.…”