  Insulating magnetic rare-earth pyrochlores related to spin ice host emergent
bosonic monopolar spinons, which obey a magnetic analogue of quantum
electrodynamics and may open a route to a magnetic analogue of electronics.
However, the energy scales of the interactions among rare-earth moments are so
low as 1 K that the possible quantum coherence can only be achieved at a
sub-Kelvin. Here, we desgin high-temperature quantum spin ice materials from
first principles. It is shown that the A-site deintercalated spinel iridate
Ir2O4, which has been experimentally grown as epitaxial thin films, is a
promising candidate for quantum spin ice with a spin-ice-rule interaction of a
few tens of meV. Controlling electronic structures of Ir2O4 through substrates,
it is possible to tune magnetic interactions so that a magnetic Coulomb liquid
persists at high temperatures.
