Carlos E. ViolBarbosa

Evidence of surface transport and weak antilocalization in a single crystal of the Bi2Te2Se topological insulator

Topological insulators are known for their metallic surface states, a result of strong spin-orbit coupling, that exhibit unique surface transport phenomenon. However, these surface transport phenomena are buried in the presence of metallic bulk conduction. We synthesized very high quality

Distinct Electronic Structure of the Electrolyte Gate-Induced Conducting Phase in Vanadium Dioxide Revealed by High-Energy Photoelectron Spectroscopy

{\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}\mathrm{Se}

Direct observation of band bending in the topological insulator Bi2Se3

single crystals by using a modified Bridgman method that possess high bulk resistivity of

Electronic and crystalline structures of zero band-gap LuPdBi thin films grown epitaxially on MgO(100)

g20

Investigation of the Mn3−δGa/MgO interface for magnetic tunneling junctions

\ensuremath{\Omega}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}

Transparent conducting oxide induced by liquid electrolyte gating

below 20 K, whereas the bulk is mostly inactive and surface transport dominates. The temperature dependence of resistivity follows an activation law like a gap semiconductor in temperature range 20--300 K. To extract the surface transport from that of the bulk, we designed a special measurement geometry to measure the resistance and found that single-crystal

Size-dependent structural and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

{\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}\mathrm{Se}

Forward scattering in hard X-ray photoelectron spectroscopy: Structural investigation of buried Mn-Ga films

exhibits a crossover from bulk to surface conduction at 20 K. Simultaneously, the material also shows strong evidence of weak antilocalization in magnetotransport owing to the protection against scattering by conducting surface states. This simple geometry facilitates finding evidence of surface transport in topological insulators, which are promising materials for future spintronic applications.

Magnetic dichroism in angular resolved hard X-ray photoelectron spectroscopy from buried magnetic layers

The development of new phases of matter at oxide interfaces and surfaces by extrinsic electric fields is of considerable significance both scientifically and technologically. Vanadium dioxide (VO2), a strongly correlated material, exhibits a temperature-driven metal-to-insulator transition, which is accompanied by a structural transformation from rutile (high-temperature metallic phase) to monoclinic (low-temperature insulator phase). Recently, it was discovered that a low-temperature conducting state emerges in VO2 thin films upon gating with a liquid electrolyte. Using photoemission spectroscopy measurements of the core and valence band states of electrolyte-gated VO2 thin films, we show that electronic features in the gate-induced conducting phase are distinct from those of the temperature-induced rutile metallic phase. Moreover, polarization-dependent measurements reveal that the V 3d orbital ordering, which is characteristic of the monoclinic insulating phase, is partially preserved in the gate-induced metallic phase, whereas the thermally induced metallic phase displays no such orbital ordering. Angle-dependent measurements show that the electronic structure of the gate-induced metallic phase persists to a depth of at least ∼40 Å, the escape depth of the high-energy photoexcited electrons used here. The distinct electronic structures of the gate-induced and thermally induced metallic phases in VO2 thin films reflect the distinct mechanisms by which these states originate. The electronic characteristics of the gate-induced metallic state are consistent with the formation of oxygen vacancies from electrolyte gating.