  The quantum spin Hall effect (QSHE) has formed the seed for contemporary
research on topological quantum states of matter. Since its discovery in
HgTe/CdTe quantum wells and AlGaAs/GaAs heterostructures, all such systems have
so far been suffering from extremely low operating temperatures, rendering any
technological application out of reach. We formulate a theoretical paradigm to
accomplish the high temperature QSHE in monolayer-substrate heterostructures.
Specifically, we explicate our proposal for hexagonal compounds formed by
monolayers of heavy group-V elements (As, Sb, Bi) on a SiC substrate. We show
how orbital filtering due to substrate hybridization, a tailored multi-orbital
density of states at low energies, and large spin-orbit coupling can conspire
to yield QSH states with bulk gaps of several hundreds of meV. Combined with
the successful realization of Bi/SiC (0001), with a measured bulk gap of 800
meV reported previously [Reis et al., 10.1126/science.aai8142 (2017)], our
paradigm elevates the QSHE from an intricate quantum phenomenon at low
temperatures to a scalable effect amenable to device design and engineering.
