Coherent energy scale revealed by ultrafast dynamics of UX${}_3$ (X=Al, Sn, Ga) single crystals

Abstract

Temperature dependence of relaxation dynamics of UX${}_3$ (X = Al, Ga, Sn) compounds is studied using time resolved pump-probe technique in the reflectance geometry. UGa${}_3$ is an itinerant antiferromagnet, while UAl${}_3$ and USn${}_3$ are spin fluctuation systems. For UGa${}_3$, our data are consistent with the formation of a spin density wave SDW gap as evidenced from the quasidivergence of the relaxation time $\tau$ near the Néel temperature $T_N$. For UAl${}_3$ and USn${}_3$, the relaxation dynamics shows a change from single exponential to two exponential behavior below a particular temperature, suggestive of coherence formation of the 5\textit{f} electrons with the conduction band electrons. This particular temperature can be attributed to the spin fluctuation temperature $T_{sf}$, a measure of the strength of Kondo coherence. Our $T_{sf}$ is consistent with other data such as resistivity and susceptibility measurements. The temperature dependence of the relaxation amplitude and time of UAl${}_3$ and USn${}_3$ were also fitted by the Rothwarf-Taylor model. Our results show ultrafast optical spectroscopy is sensitive to c-\textit{f} Kondo hybridization in the \textit{f}-electron systems.

6 pages, 5 figures

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• Anomalous Femtosecond Quasiparticle Dynamics of Hidden Order State in URu${}_2$Si${}_2$
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Cited by in corpus (1)

• Optical spectroscopy and ultrafast pump-probe studies on the heavy fermion compound CePt${}_2$In${}_7$