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Harold Hwang studies electronic phenomena in oxide materials and their interfaces. His Stanford publication record includes work on electronic reconstruction and emergent states at oxide interfaces, where local symmetry and charge distribution can differ from those of either bulk material.^[ref]

He also coauthored the indium tin oxide study of band nonparabolicity.^[ref] The broader experimental idea is that an interface is a physical region with its own structure and boundary conditions. Measuring a conducting layer at a boundary therefore raises questions about charge location, thickness and the adjoining materials, rather than being fully described by averaging the two bulk conductivities. Local structural and electronic measurements can test those distinctions.

Hongtao Yuan researches electronic and optoelectronic behavior at material interfaces. His Nanjing University profile describes electric-field control of charge, spin and orbital behavior in low-dimensional systems and records his earlier Stanford work with Yi Cui and Harold Hwang.^[ref]

He also coauthored the indium tin oxide study of band nonparabolicity.^[ref] A basic experimental distinction in this field is between changing the number of carriers electrically and changing a material's chemical composition. Both can alter conductivity, but their structural effects and reversibility need not be the same. Comparing transport and optical response helps identify what has changed beyond a single resistance value.

By Xiaoge Liu, Junghyun Park, Ju-Hyung Kang, Hongtao Yuan, Yi Cui, Harold Hwang and Mark Brongersma. Applied Physics Letters 105, 181117 (2014). Figure 3: Hall measurements, carrier density, optical plasma frequency and mobility. Byline corroborated by Stanford SIMES: simes.stanford.edu/publications/quantum?page=21