Andrea MarkelzAssistant ProfessorPulsed Terahertz Spectroscopy of Solid State and Biomolecular materials | 
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Contact Information
Brief CV
- B.A., University of California, Berkeley (1987)
- Ph.D., University of California, Santa Barbara (1995)
Selected Publications
- A.G. Markelz and E.J. Heiweil. "Temperature Dependent THz Output from Semi-Insulting GaAs Photoconductive Switches." Appl. Phys. Lett. 72, 2229 (1998).
- A.G. Markelz, N.G. Asmar, E.G. Gwinn and Berinder Brar. "Energy relaxation time in InAs/A11-xGaxSb quantum wells." Appl. Phys. Lett. 72, 2439 (1998).
- A.G. Markelz, N.G. Asmar, E.G. Gwinn and Berinder Brar. "Impact Ionization in InAs quantum wells with Far Infrared Illumination." Appl. Phys. Lett. 69, 3975 (1996).
- G. Markelz and E.G. Gwinn. "Charge Density and Intensity dependence of third order susceptibility in Quasi-2D systems." J. Appl. Phys. 80, 2533 (1996).
- "Third harmonic generation in GaAs/A1GaAs superlattice in the Bloch oscillator regime." M.C. Wanke, A.G. Markelz, K. Unterrainer, S. J. Allen and R. Bhaat, in Hot Carriers in Semiconductors, edited by K. Hess, J. P. Leburton and U. Ravaioli (Picnum Press, 1996).
Research Interests
My present research concerns exploiting the technique of pulsed terahertz spectroscopy (PTS) to study carrier and phonon dynamics in solid state materials and energy transfer to conformational vibrational modes in biomolecules.PTS is a versatile technique that uses ultrafast lasers (10-20 fs pulse widths) to generate low frequency broad band (0.2-3.0 THz, n ~ 7 - 100 cm-1, l ~ 1.5 - 0.1 mm) pulsed output (~ 1 ps pulse width). A coherent detection scheme allows for efficient determination of the complex dielectric response in a frequency region that overlaps dissipation mechanisms and lattice vibrational modes in solid state materials, and conformational vibrational modes in large macromolecules. Since the pulsed THz output is synchronized to the near infrared ultrafast generating laser, the system is also used for time resolved pump/probe measurements.
Current Projects
- The solid state research is focussed on two areas. Standard materials characterization is being performed on several perovskite systems: high Tc superconductors, colossal magnetoresistance materials and ferroelectrics. These studies are necessary to both better understand phonon-carrier interactions that underlie the novel properties of these material systems and to characterize the response of these materials at operating frequencies of technological interest. A second area of solid state research is nonlinear carrier dynamics in two dimensional electron systems in III-V semiconductor systems. In particular we are trying to understand how dissipation contributes to nonlinear response.
- The biomolecular research concerns using low frequency spectroscopy as a probe to the conformational state of a protein. The conformational state, i.e. the three-dimensional arrangement of the polypeptide chain, is critical to the function of the protein. Using PTS as a probe to this 3D structure opens a new avenue for investigations of the energy transfer mechanisms involved during the process of conformational change.
