Spectroscopy of Novel Materials
Using light to study fundamental properties of new materials for tomorrow’s technology
Spectroscopy is an enhanced form of seeing-- one of several that have critically influenced the development of our sciences. Telescopes, microscopes and spectroscopes each enable enhanced vision. Telescopes allowed Galileo to observe moons circling Jupiter, augmenting his perspection in a way that enabled him to envision the earth circling the sun, rather than at the center of the universe. Microscopy provides a powerful window into the domain of very small things, and has been essential to the development of biology and the nanosciences. High and low-speed photography have opened new vistas related to very fast and very slow processes, enabling access to previously unseen and unknown domains.
Spectroscopy provides another important and powerful manner in which to extend our perception. According to the laws of quantum physics, electromagnetic radiation, or light, is made up of small wave-like particles called photons. Each photon carries a microscopic amount of energy. That energy is inversely related to the photon’s wavelength . Spectroscopy is a nuanced form of seeing in which one separates photons according to their energy or wavelength.
Color vision provides a familiar example of spectroscopy. The colors: red, orange, yellow, green, blue and violet, each correspond to progressively higher photon energies (shorter wavelengths). Color vision evolved more than once and probably for different purposes in different species†. This may reflect the potential power and importance of spectroscopic (color) vision. Lizards and some monkeys have better color vision than we do (more ability to distinguish photon energies). Selection of fruit and mates are likely to have been applications which influenced the evolution of our color vision.
In physics, biology and chemistry an advanced form of “color vision” known as spectroscopy provides a powerful technique for studying matter in many forms. In our laboratory we use such spectroscopy to go beyond the ancient science of fruit selection to the study of modern materials, focussing on novel componds with unusual, interesting and potentially useful electron or phonon dynamics.
The range of our spectroscopy extends from photon energies of about 0.002 eV to 6 eV. This encompasses the visible range (in which color vision operates), as well as the infrared and part of the ultra violet (UV). The term infrared refers to the part of the electromagnetic spectrum with photon energies below those of visible light (that is, photon energies less than 2 eV, which correspond to red light). UV refers to the spectral region above the visible. (Photon energies above 3.5 eV (violet, or purple, light)).
In our laboratory we often measure the reflectivity of materials (how shiny is it?). This provides surprisingly profound and detailed information regarding the fundamental nature of the electron dynamics in a material. Another approach is to measure transmission (how transparent is it?). In both cases the photon flux is measured as a function of energy (or wavelength); that is the essence of spectroscopy. Some of our recent work focusses on studying the reflectivity of YbIn1-xAgxCu4, a “heavy electron” material with a Kondo-resonance excitation in the infrared, and on ZrW2O8, a compound which contracts when it is heated and exhibits very unusual phonon dynamics which may hold the key to understanding its anomalous contraction.
† Richard Dawkins, The Ancestor's Tale, Houghten Mifflin, 2004
Soft Manifold Dynamics Behind Negative Thermal Expansion, Z. Schlesinger, J. A. Rosen, J. N. Hancock, A. P. Ramirez, Phys. Rev. Lett. 101, 15501 (2008) [download pdf]
Ferromagnetism in the Mott insulator Ba2NaOsO6, Erickson, A.S., Misra, S., Miller, G.J., Gupta, R.R., Schlesinger, Z., Harrison, W.A., Kim, J.M., Fisher, I.R., Phys. Rev. Lett., 99, 16404, (2007)
Infrared dynamics of YbIn1-xAgxCu4: Kondo scaling, sum rules and temperature dependence, J.N. Hancock, T. McKnew, Z. Schlesinger, J.L. Sarrao, and Z. Fisk, Phys. Rev. B 73, 125119 (2006) [download pdf]
Optically probing the Kondo resonance in YbIn1-xAgxCu4,, J.N. Hancock, T. McKnew, Z. Schlesinger et al., Physica B, Condensed Matter 359, 239-241 (2005) [download pdf]
Unusual low-energy phonon dynamics in the negative thermal expansion compound ZrW2O8. J.N. Hancock, C.M. Turpen, Z. Schlesinger, G.R. Kowach, and A.P. Ramirez, Phys. Rev. Lett. 93, 225501 (2004) [download pdf]
Improving power efficiencies in polymer-polymer blend photovoltaic. A.J. Breeze, Z. Schlesinger, S.A. Carter, H. Tillmann, and H.H. Horhold. Solar Energy Materials and Solar Cells 83, 263 (2004) [download pdf]
Kondo scaling in the optical response of YbIn1-xAgxCu4, Jason N. Hancock, Tim McKnew, Zack Schlesinger, John L. Sarrao, Zach Fisk. Phys. Rev. Lett. 92, 19700 (2004) [download pdf]
Nanoparticle-polymer and polymer-polymer blend composite photovoltaics, A.J. Breeze, Z. Schlesinger, S.A. Carter, H. Horhold, H. Tillmann, D.S. Ginley, and P.J. Brock. Proceedings of SPIE 4108, pp. 57-61 (2001) [download pdf]
Charge transport in TiO2 - MEH-PPV polymer photovoltaics, A.J. Breeze, Z. Schlesinger, S.A. Carter and P.J. Brock, Phys. Rev. B 64, 125205 (2001) [download pdf]
Fractional power-law conductivity in SrRuO3 and its consequences, J.S. Dodge, C.P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J.W. Reiner, and M.R. Beasley, Phys. Rev. Lett. 85, 4932-4933 (2000) [download pdf]
Optical study of the electronic phase-transition of strongly correlated YbInCu4, Sean R. Garner, Jason N. Hancock, Yvonne W. Rodriguez, Zack Schlesinger, Benno Bucher, Zack Fisk, John L. Sarrao, Phys. Rev. B 62, 4478-4482(2000) [download pdf]
Efficient Titanium Oxide/Conjugated Polymer Photovoltaics for Solar Energy Conversion, Alexi C. Arango, Larry R. Johnson, Valery N. Bliznyuk, Zack Schlesinger, Sue A. Carter, and Hans-H. Horhold, Advanced Materials, V 12, 1689-1692 (2000) [download pdf]
Non-Fermi liquid behavior of SrRuO3 - evidence from infrared conductivity, P. Kostic, Y. Okada, Z. Schlesinger, J.W. Reiner, L. Klein, A. Kapitulnik, T.H. Geballe, and M.R. Beasley, Phys. Rev. Lett. 81, 2498-2501 (1998) [download pdf]
Is FeSi a Kondo insulator?, Z. Schlesinger, Z. Fisk, Hai-Tao Zhang, M.B. Maple. Physica B 237-238, 460-462 (1997) [download pdf]
Charge dynamics of Ce based compounds: connection between the mixed-valent and Kondo-insulator states, B. Bucher, Z. Schlesinger, D. Mandrus, Z. Fisk, J. Sarrao, J. F. DiTusa, C. Ogelsby, G. Aeppli and E. Bucher. Phys. Rev. B 53, 2948-2952 (1996) [download pdf]
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