  We study nonequilibrium transport in various open quantum systems whose
systems and leads/baths are made of topological superconductors (TSs),
semiconductors, and metals. Using quantum Langevin equations and Green's
function method, we derive exact expressions for steady-state electrical,
thermal, and spin current at the junctions between a system and leads. We
validate these current expressions by comparing them with the results from
direct time-evolution simulations. We then show how an electrical current
injected in TS wires divides into two parts carried by single electronic
excitations and Cooper pairs. We further show ballistic thermal transport in an
open TS wire in the topological phase under temperature or voltage bias. The
thermal current values grow significantly near the topological phase
transition, where thermal conductance displays a sharp quantized peak as
predicted earlier. We relate the quantized thermal conductance to the
zero-frequency thermoelectric transmission coefficient of the open TS wire. We
also observe a large thermoelectric current near the topological transition of
the TS wires. We introduce a differential spin conductance which displays a
quantized zero-bias peak at zero temperature for a spinful TS wire in the
topological phase. The role of superconducting baths in transport is
demonstrated by thoroughly examining the features of zero-temperature
differential electrical conductance and thermal conductance in open systems
with TS baths. Our new thermoelectric and spin transport findings in various
two-terminal geometries are beneficial to the present challenges in probing the
emergence of Majorana quasi-particles in experiments.
