Ultrafast x-ray diffraction thermometry measures the influence of spin excitations on the heat transport through nanolayers - Archive ouverte HAL
Article Dans Une Revue Physical Review B: Condensed Matter (1978-1997) Année : 2017

Ultrafast x-ray diffraction thermometry measures the influence of spin excitations on the heat transport through nanolayers

Résumé

We investigate the heat transport through a rare earth multilayer system composed of yttrium (Y), dysprosium (Dy), and niobium (Nb) by ultrafast x-ray diffraction. This is an example of a complex heat flow problem on the nanoscale, where several different quasiparticles carry the heat and conserve a nonequilibrium for more than 10 ns. The Bragg peak positions of each layer represent layer-specific thermometers that measure the energy flow through the sample after excitation of the Y top layer with fs-laser pulses. In an experiment-based analytic solution to the nonequilibrium heat transport problem, we derive the individual contributions of the spins and the coupled electron-lattice system to the heat conduction. The full characterization of the spatiotemporal energy flow at different starting temperatures reveals that the spin excitations of antiferromagnetic Dy speed up the heat transport into the Dy layer at low temperatures, whereas the heat transport through this layer and further into the Y and Nb layers underneath is slowed down. The experimental findings are compared to the solution of the heat equation using macroscopic temperature-dependent material parameters without separation of spin and phonon contributions to the heat. We explain why the simulated energy density matches our experiment-based derivation of the heat transport, although the simulated thermoelastic strain in this simulation is not even in qualitative agreement.
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Dates et versions

hal-02889052 , version 1 (03-07-2020)

Identifiants

Citer

A. Koc, M. Reinhardt, A. von Reppert, M. Rössle, W. Leitenberger, et al.. Ultrafast x-ray diffraction thermometry measures the influence of spin excitations on the heat transport through nanolayers. Physical Review B: Condensed Matter (1978-1997), 2017, 96 (1), pp.014306. ⟨10.1103/PhysRevB.96.014306⟩. ⟨hal-02889052⟩
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