We present a detailed theoretical study of the ultrafast quasiparticle relaxation dynamics observed in normal metals and heavy-fermion materials with femtosecond time-resolved optical pump-probe spectroscopy. For normal metals, a nonthermal electron distribution gives rise to a temperature-(T) independent electron-phonon relaxation time at low temperatures, in contrast to the T−3-divergent behavior predicted by the two-temperature model. For heavy-fermion compounds, we find that the blocking of electron-phonon scattering for heavy electrons within the density-of-states peak near the Fermi energy is crucial to explain the rapid increase of the electron-phonon relaxation time below the Kondo temperature. We propose the hypothesis that the slower Fermi velocity compared to the sound velocity provides a natural blocking mechanism due to energy and momentum-conservation laws.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jan 30 2004|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics