  While current-induced torque by orbital current has been experimentally found
in various structures, evidence for its reciprocity has been missing so far.
Here, we report experimental evidence of strong inverse orbital torque in
YIG/Pt/CuOx (YIG = Y3Fe5O12) mediated by spin-orbital entangled electronic
states in Pt. By injecting spin current from YIG to Pt by the spin pumping via
ferromagnetic resonance and by the spin Seebeck effect, we find a pronounced
inverse spin Hall effect-like signal. While a part of the signal is explained
as due to the inverse spin-orbital Hall effect in Pt, we also find substantial
increase of the signal in YIG/Pt/CuOx structures compared to the signal in
YIG/Pt. We attribute this to the inverse orbital Rashba-Edelstein effect at
Pt/CuOx interface mediated by the spin-orbital entangled states in Pt. Our work
paves the way toward understanding of spin-orbital entangled physics in
nonequilibrium and provides a way for electrical detection of the orbital
current in orbitronic device applications.
