Several quantum spin liquid candidate materials, such as 𝛼RuCl3 and
1T-TaSe2, are exfoliable, so that it is possible to investigate 2D samples
which avoid the manifestation of bulk properties that might disrupt the
quantum spin liquid phase. In this phase the material is a Mott insulator impenetrable to direct electric probes such as charge currents.
Despite this, we propose an experimental setup that will allow to use
non-local electrical probes to gain information on the transport properties of gapless quantum spin liquids. The proposed setup is a spinon
induced drag experiment, that consists in interfacing two metallic films
separated by a layer of quantum spin liquid. A current is injected in one
of the two layers (active layer) and a voltage is measured on the second
(passive) metallic film. The electrons of both layers interact with the
spinons via Kondo interaction, thus allowing momentum transfer from
the active to the passive layer. We calculate, both for a U(1) and a
𝑍2 spin liquids, the drag resistivity in the framework of the linearized
quantum Boltzmann equation derived from the Keldysh formalism. In
this framework the three layers are out of thermodynamic equilibrium.
We further confront the results obtained with the equilibrium case and
with the results of standard Coulomb drag.