Simultaneous measurement of circular dichroism and Faraday rotation at terahertz frequencies utilizing electric field sensitive detection via polarization modulation.

A far-infrared system measures the full complex Faraday angle, the rotation as well as the ellipticity, with an unprecedented accuracy of 10 microrad/T. The system operates on several far-infrared laser lines in the spectral range from 0.3 to 6 THz and produces results as a continuous function of temperature from 10 to 310 K and applied fields between +/-8 T. Performance of the instrument is demonstrated by measurements on a GaAs two-dimensional electron gas heterostructure and Bi(2)Sr(2)CaCu(2)O(8+x) single crystal.

Optical plasmonic resonances in split-ring resonator structures: an improved LC model.

We systematically investigate the resonant behavior of arrays of Ag nano-structures ranging from isolated simple rods, to U-shapes, to single split ring structures. We show that the lowest order plasmonic resonance associated with a rod red shifts as we create a U and SRR into the position normally associated with a simple LC mode. A second mode red shifts and grows in intensity as we extend the arms of the U-shape, and a third mode appears in the spectra as we close the arms and form a split ring structure. We performed simulations of the structures and examine the E-field and current density. The simulations show that the current path is different for these modes. We examine the behavior of the lowest order mode in detail, discuss the effects of skin depth, and present an improved LC model to describe this resonance.

Magneto-optical evidence for a gapped fermi surface in underdoped YBa2Cu3O6+x.

The infrared (900-1100 cm(-1)) Faraday rotation and circular dichroism are measured in the normal state of underdoped High T(c) superconductors and used to study the magnetotransport. YBa2Cu3O6+x thin films are investigated in the temperature range 10-300 K in magnetic fields up to 8 T and as a function of oxygen concentration. A dramatic increase of the Hall frequency is observed for underdoped samples, which is not consistent with the approach to a Mott transition but is consistent with a partial gapping of the Fermi surface as predicted in density wave models.

Spectral measurement of the Hall angle response in normal state cuprate superconductors.

We measure the temperature and frequency dependence of the complex Hall angle for normal state YBa(2)Cu(3)O(7) films from dc to far-infrared frequencies (20-250 cm(-1)) using a new modulated polarization technique. We determine that the functional dependence of the Hall angle on scattering does not fit the expected Lorentzian response. We find spectral evidence supporting models of the Hall effect where the scattering Gamma(H) is linear in T, suggesting that a single relaxation rate, linear in temperature, governs transport in the cuprates.