  Quantum spin-liquid van der Waals magnets such as TaS$_2$, TaSe$_2$, and
RuCl$_3$ provide a natural platform to explore new exotic phenomena associated
with spinon physics, whose properties can be controlled by exchange proximity
with ferromagnetic insulators such as CrBr$_3$. Here we put forward a twisted
van der Waals heterostructure based on a quantum spin-liquid bilayer
encapsulated between ferromagnetic insulators. We demonstrate the emergence of
spinon flat bands and topological spinon states in such heterostructure, where
the emergence of a topological gap is driven by the twist. We further show that
the spinon bandstructure can be controlled via exchange proximity effect to the
ferromagnetic leads. We finally show how by combining small magnetic fields
with tunneling spectroscopy, magnetically encapsulated heterostructures provide
a way of characterizing the nature of the quantum spin-liquid state. Our
results put forward twisted quantum spin-liquid bilayers as potential platforms
for exotic moire spinon phenomena, demonstrating the versatility of magnetic
van der Waals heterostructures.

Strongly Correlated Electrons;Mesoscale and Nanoscale Physics;Materials Science