Ultrafast quasiparticle relaxation dynamics in normal metals and heavy-fermion materials
نویسندگان
چکیده
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-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.
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