Nonequilibrium electron dynamics in a solid with a changing nodal excitation gap

Abstract

We develop a computationally inexpensive model to examine the dynamics of boson-assisted electron relaxation in solids, studying nonequilibrium dynamics in a metal, in a nodal superconductor with a stationary density of states, and in a nodal superconductor where the gap dynamically opens. In the metallic system, the electron population resembles a thermal population at all times, but the presence of even a fixed nodal gap both invalidates a purely thermal treatment and sharply curtails relaxation rates. For a gap that is allowed to open as electron relaxation proceeds, effects are even more pronounced, and gap dynamics become coupled to the dynamics of the electron population.Comparisons to experiments reveal that phase-space restrictions in the presence of a gap are likely to play a significant role in the widespread observation of coexisting femtosecond and picosecond dynamics in the cuprate high-temperature superconductors.

Dehybridization of f and d states in the heavy-fermion system YbRh2Si2

“…Fig. 4(b) shows that the intensity in region I above E F increases linearly with increasing T e , confirming the expected linear relationship for a thermalized electron T e (K) population [35]. In the discussion of Fig.…”

“…The overall time resolution of our experiment of 160 fs is given by the width of the cross correlation (XC) at E − E F = 0.3 eV. Region I tracks the intensity increase above E F and is expected to be proportional to T e for a thermalized electron distribution [35]. Indeed, both quantities track each other closely and peak at 0.2 ps before decaying on a ps time scale.…”

Ultrafast dynamics of electron-phonon coupling in a metal

“…Indeed in a metallic system, the electron population resembles a thermal population that is the case of a nonsuperconducting cuprate. In contrast, when a gap opens in a superconducting cuprate, electron relaxation dynamics become coupled to the dynamics of the electron population and phase restriction processes kick in, leading to coexisting femtosecond and picosecond dynamics [18]. Clearly these results suggest that there are several mechanism at play that could provide new insights on the nature of the superconductivity and ask for more detailed theoretical works.…”

Particle-Hole Asymmetry in the Cuprate Pseudogap Measured with Time-Resolved Spectroscopy

“…This enhanced width does not represent thermal excitations but rather the Bogoliubov mixing of electronlike and holelike excitations. Pumping is known to suppress the superconducting gap [34,35]; thus, as we approach T e = T c the value of w eff may actually decrease with the temperature, if ∆ SC >> k B T c . Based on these considerations Fig.…”