P.-C. Ho

Infrared spectroscopy and nano-imaging of the insulator-to-metal transition in vanadium dioxide

We present a detailed infrared study of the insulator-to-metal transition IMT in vanadium dioxide VO2 thin films. Conventional infrared spectroscopy was employed to investigate the IMT in the far field. Scanning near-field infrared microscopy directly revealed the percolative IMT with increasing temperature. We confirmed that the phase transition is also percolative with cooling across the IMT. We present extensive near-field infrared images of phase coexistence in the IMT regime in VO2. We find that the coexisting insulating and metallic regions at a fixed temperature are static on the time scale of our measurements. A distinctive approach for analyzing the far-field and near-field infrared data within the Bruggeman effective medium theory was employed to extract the optical constants of the incipient metallic puddles at the onset of the IMT. We found divergent effective carrier mass in the metallic puddles that demonstrates the importance of electronic correlations to the IMT in VO2. We employ the extended dipole model for a quantitative analysis of the observed near-field infrared amplitude contrast and compare the results with those obtained with the basic dipole model.

Heavy-fermion behavior, crystalline electric field effects, and weak ferromagnetism in Sm Os 4 Sb 12

The filled skutterudite compound

Superconductivity and crystalline electric field effects in the filled skutterudite series Pr ( Os 1 − x Ru x ) 4 Sb 12

\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}

Ferromagnetism and possible heavy-fermion behavior in single crystals of Nd Os 4 Sb 12

was prepared in single-crystal form and characterized using x-ray diffraction, specific-heat, electrical resistivity, and magnetization measurements. The

Non-Fermi liquid behavior in the filled skutterudite compound CeRu4As12

\mathrm{Sm}{\mathrm{Os}}_{4}{\mathrm{Sb}}_{12}

Multiple ordered phases in the filled skutterudite compound PrOs4As12

crystals have the

Crystalline electric field effects in the filled skutterudite compound PrOs4P12

\mathrm{La}{\mathrm{Fe}}_{4}{\mathrm{P}}_{12}

The filled skutterudite CeOs4As12: A hybridization gap semiconductor

-type structure with lattice parameter

Ambient-pressure bulk superconductivity deep in the magnetic state of Ce Rh In 5

a=9.3085\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}

Probing the superconductivity of PrPt4Ge12 through Ce substitution

. Specific-heat measurements indicate a large electronic specific-heat coefficient of