Ultrafast optical pump terahertz-probe spectroscopy of strongly correlated electron materials.
- Richard D.
- Verner K.
- Stuart A.
We have used optical-pump far-infrared probe spectroscopy to probe the low energy electron dynamics of high temperature superconductors and colossal magnetoresistance manganites. For the superconductor YBa2Cu3O7, picosecond conductivity measurements probe the interplay between Cooper-pairs and quasiparticles. In optimally doped films, the recovery time for long-range phase-coherent pairing increases from {approx}1.5 ps at 4K to {approx}3.5 ps near Tc, consistent with the closing of the superconducting gap. For underdoped films, the measured recovery time is temperature independent (3.5 ps) in accordance with the presence of a pseudogap. Ultrafast picosecond measurements of optically induced changes in the absolute conductivity of La0:7M0:3MnO3 thin films (M = Ca, Sr) from 10K to {approx}0.9Tc reveal a two-component relaxation. A fast, {approx}2 ps, conductivity decrease arises from optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. Our results indicate that for T<<Tc, the conductivity is determined by incoherent phonons while spin fluctuations dominate near Tc.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 975709
- Report Number(s):
- LA-UR-01-4821; TRN: US1006764
- Resource Relation:
- Conference: "Submitted to: Invited paper for Proceedings of the 26th International Conference on Infrared and Millimeter Waves"
- Country of Publication:
- United States
- Language:
- English
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