Controlling thermal properties is central to many applications, such as thermoelectric energy conversion and the thermal management of integrated circuits. Progress has been made over the past decade by structuring materials at different length scales, but a clear relationship between structure size and thermal properties remains to be established. The main challenge comes from the unknown intr...

Fermi liquid theory is remarkably successful in describing the transport and optical properties of metals; at frequencies higher than the scattering rate, the optical conductivity adopts the well-known power law behavior σ1(ω) ∝ ω(-2). We have observed an unusual non-Fermi liquid response σ1(ω) ∝ ω(-1±0.2) in the ground states of several cuprate and iron-based materials which undergo electronic...

Recent progress in experimental techniques has made it possible to extract detailed information on dynamics of carriers in a correlated electron material from its optical conductivity, [Formula: see text]. This review consists of three parts, addressing the following three aspects of optical response: (1) the role of momentum relaxation; (2) [Formula: see text] scaling of the optical conductivi...

Temperature-dependent ~300–10 K! reflectance measurements were made on h-Mo4O11 and g-Mo4O11 in the conducting b-c plane in the frequency range 30–8000 cm, for light polarized both parallel and perpendicular to the charge density wave ~CDW! direction ~b axis!. The optical conductivity was determined from a Kramers-Kronig analysis of the reflectance. The data clearly show strong suppression of t...

In2O3 exhibits a dramatic increase in solubility of SnO2 and ZnO when they are cosubstituted into In2O3. The resultant material, In2-2xSnxZnxO3-δ with x ) 0-0.4, displays the same order of magnitude conductivity and transparency compared with bulk ITO (tindoped indium oxide). Rapid quenching of In2-2xSnxZnxO3-δ raises the conductivity and widens the optical bandgap while lowering the optical tr...

A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that i...

We report on a study of the optical conductivity of single crystals of the high-Tc superconductor YBa2Cu4O8 in which superconductivity is suppressed by random substitution of Cu with Zn. The a-axis infrared spectrum, which is a direct measure of the charge dynamics in the CuO2 planes, is dominated by a bound state at ø120 cm21. This indicates that the low-energy electronic states are on the ver...

~-phase organic conductors with bidimensional layers of orthogonal molecular dimers are modelled by tetramers and hexamers of appropriate geometry. The complex conductivity is calculated within the Hubbard model including the electron-intramolecular vibration coupling. The polarized optical conductivity data of two ~-phase charge-transfer salts of b~s-(ethylenedithio)-tetrathiafulvalene: ~-(BED...

We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Jo...

The optical absorptivities of oriented single crystals of hcp Gd, Tb, Dy, Ho, Er, Tm, and Lu were measured at 4.2 K between 0.2 and 4.4 eV. Polarized radiation was used to reveal the optical anisotropy. Systematic movement of structures in the absorptivity and optical conductivity was observed as a result of trends within sp and d bands. Low-energy structures were related to effects of s−f exch...