Electronic Transport of Thin Crystals in Ruthenium Chloride

Ruthenium chloride (RuCl3) is a 4d halide and relativistic Mott insulator where Ruthenium atoms form a honeycomb lattice. Electronic interactions and spin-orbit coupling work together to give RuCl3 its insulating behavior. This brings forth exciting physics predicted in the frame of the Kitaev model including exotic ground states like zigzag ordering and quantum spin liquids. We prepared samples for experiments that aim to test for these exotic states. Nanofabrication techniques such as mechanical exfoliation, electron beam lithography, and thin film deposition, were used to obtain crystals of about 20 nm in thickness to make devices for testing. Preliminary electronic transport measurements were performed. In the low bias regime, all samples presented a thermal activation energy of ~80 meV. In the high bias regime, electronic transport was ruled by Frenkel-Poole emission. When large vertical electric fields were applied via a back-gate voltage, a higher bias voltage was needed to thermally activate charge carriers. The presence of a vertical electric field seemed to impede Frenkel-Poole emission. Larger fields will be needed to reach either the valence band or the conduction band of RuCl3 which has an energy band gap of at least 1.7 eV, probed by angle resolved photoemission spectroscopy (ARPES). More powerful gating techniques should be tested such as electrostatic ionic liquid gating, which will allow probing magnetic ordered ground states, predicted in the frame of the Kitaev model