Transport study of graphene adsorbed with indium adatoms

Enhancement of the spin-orbit coupling in graphene may lead to various topological phenomena and also find applications in spintronics. Adatom adsorption has been proposed as an effective way to achieve the goal. In particular, great hope has been held for indium in strengthening the spin-orbit coupling and realizing the quantum spin Hall effect. To search for evidence of the spin-orbit coupling in graphene adsorbed with indium adatoms, we carry out extensive transport measurements. It is found that indium adatoms dope graphene and introduce significant Coulomb scattering. No signature of the spin-orbit coupling is observed in the weak localization magnetoconductance and nonlocal spin Hall effect. Possible explanations are discussed.