Quantum Material Properties of 4d and 5d Transition Metal Oxides and Potential Applications.

摘要

This grant enabled the exploration of 4d and 5d transition metal oxides, in particular, ruthenates, as well as novel two-dimensional (2D) electronic materials, all featuring interesting physical properties and/or structure-property relationships. Specifically, we carried out electrical and magneto transport measurements on La4Ru6O19, BaRuO3, and Sr2RuO4 single crystals, and pursued the characterization, device fabrication, as well as the exploration of the potential uses of 2D electronic materials including graphene and NbSe2. La4Ru6O19 showed a ferromagnetic quantum criticality near ambient pressure; four-layered hexagonal (4H) and nine-layered rhombohedral (9R) BaRuO3 possess interesting structure-property relationships, with the strong one-dimensional character in the 9R structure leads to clear deviation from the metallic behavior seen in the 4H structure. The Nernst effect signal in the normal state of Sr2RuO4 is large which decreases linearly as a function of temperature, possibly related to the band-dependent magnetic fluctuation, which was suppressed by the emergence of coherence at low temperatures. We observed strong magneto conductance fluctuations in few layer graphene near the charge neutral point, and novel electronic states at the interface between monolayer and bilayer graphene. For NbSe2, we found that the CDW was suppressed in the atomically thin NbSe2 while SC survives down to two atomic layers.