%0 Journal Article %J Physical Review B %D 2020 %T Linear dichroism infrared resonance in overdoped, underdoped, and optimally doped cuprate superconductors %A Mukherjee, A. %A Seo, J. %A Arik, M. M. %A Zhang, H. %A Zhang, C. C. %A Kirzhner, T. %A George, D. K. %A Markelz, A. G. %A Armitage, N. P. %A Koren, G. %A Wei, J. Y. T. %A Cerne, J. %K Materials Science %K Physics %X

By measuring the polarization changes in terahertz, infrared, and visible radiation over an extended energy range (3-2330 meV), we observe symmetry breaking in cuprate high-temperature superconductors over wide energy, doping, and temperature ranges. We measure the polarization rotation (Re[theta(F)]) and ellipticity (Im[theta(F)]) of transmitted radiation through thin films as the sample is rotated. We observe a twofold rotational symmetry in theta(F), which is associated with linear dichroism (LD) and occurs when electromagnetic radiation polarized along one direction is absorbed more strongly than radiation polarized in the perpendicular direction. Such polarization anisotropies can be generally associated with symmetry breakings. We measure the amplitude of the LD signal and study its temperature, energy, and doping dependence. The LD signal shows a resonant behavior with a peak in the few hundred meV range, which is coincident with the midinfrared optical feature that has been associated with the formation of the pseudogap state. The strongest LD signal is found in underdoped films, although it is also observed in optimally and overdoped samples. The LD signal is consistent with an electronic nematic order which is decoupled from the crystallographic axes as well as novel magnetoelectric effects.

%B Physical Review B %V 102 %P 6 %8 Aug %@ 2469-9950 %G English %9 Article %M WOS:000562627700004 %] 054520 %R 10.1103/PhysRevB.102.054520 %0 Journal Article %J Physical Review E %D 2005 %T Large oxidation dependence observed in terahertz dielectric response for cytochrome c %A Chen, J. Y. %A Knab, J. R. %A Cerne, J. %A Markelz, A. G. %K absorption %K binding %K conformation %K dna %K dynamics %K heart ferricytochrome-c %K modes %K Physics %K protein flexibility %K spectroscopy %K state %X

Far infrared dielectric response is used to characterize the collective mode density of states for cytochrome c as a function of oxidation state and hydration using terahertz time domain spectroscopy. A strong absorbance and refractive index increase was observed with the oxidation. A simple phenomenological fitting using a continuous distribution of oscillators reproduces the frequency dependence of the complex dielectric response as well as demonstrates quantitative agreement with a uniform increase in either mode density or polarizability with oxidation in the 5-80 cm(-1) frequency range. Hydration dependence measurements find that a difference in the equilibrium water content for ferri and ferro cytochrome c is not sufficient to account for the large change in terahertz response. The large dielectric increase at terahertz frequencies with oxidation suggests either a significant global softening of the potential and/or a significant increase in polarizability with oxidation.

%B Physical Review E %V 72 %P 4 %8 Oct %@ 1539-3755 %G English %9 Article %M WOS:000232930600005 %] 040901 %R 10.1103/PhysRevE.72.040901