Condensed Matter Seminar

Norman Tolk
Vanderbilt University

Tuesday, January 20, 2009; 4:00 pm in JFB 334

Carrier/Spin and Coherent Phonon Dynamics Using Intense, Tunable, Ultra-fast Lasers

Recent progress in laser technology has increased experimental capabilities to an extent undreamed of even a few years ago. With the lasers now available, it is possible to fulfill the long-sought goal of modern science to characterize and coherently control the motion and electronic properties of condensed matter on atomic and molecular scales. Multiple ultra-fast laser pulses, phase-correlated spatially and/or temporally, can be applied to a material system to coherently interact with phonons and electrons in a non-equilibrium manner. Our group has pioneered such techniques, motivated by the goal of selectively, remotely and non-thermally creating coherent acoustic phonon (CAP) waves, which travel to an isolated thin layer or array of quantum structures to be studied. Additional laser pulses are timed to correlate temporally, spatially and in phase with the coherent phonons as they arrive at a layer of interest in order to either characterize the material or electronically modify it. Recent advances in the application of this approach to semiconductor heterostructures will be discussed including (a) pump-probe magnetic optical Kerr effect measurements to monitor spin and carrier dynamics in ultra-thin diluted magnetic semiconductor layers^1,2, and (b) studies of non-equilibrium coherent acoustic phonons (CAP) in GaMnAs, silicon and diamond structures³.

References:
1. "Ultrafast Laser-Induced Coherent Spin Dynamics In Ferromagnetic GaMnAs/GaAs Structure," J. Qi, Y. Xu, A. Steigerwald, , X. Liu, J. K. Furdyna, and I. E. Perakis, N. Tolk. Phys. Rev. B 79 (4), Jan 2009.
2. "Coherent magnetization precession in GaMnAs induced by ultrafast optical excitation," J. Qi, Y. Xu, N. Tolk, X. Liu, J. K. Furdyna, and I. E. Perakis, Applied Physics Letters 91 (11): Art. No. 112506 Sep 10 2007.
3. "Near-bandgap wavelength dependence of long-lived traveling coherent longitudinal acoustic phonons in GaSb-GaAs heterostructures" Miller, J. K., Qi, J., Xu, Y., Cho Y., Liu, X., Furdyna, J. K. , Perakis, I., Shahbazyan, T. V. , and Tolk, N., Phys. Rev. B 74 (11), Art. No 113313 Sep 2006.