All-optical nonthermal pathway to stabilizing magnetic Weyl semimetals in pyrochlore iridates

Nature Communications 9,4452, (2018)

All-optical nonthermal pathway to stabilizing magnetic Weyl semimetals in pyrochlore iridates

Gabriel E. Topp, Nicolas Tancogne-Dejean, Alexander F. Kemper, Angel Rubio, Michael A. Sentef

Nonequilibrium many-body dynamics is becoming a central topic in condensed matter physics. Floquet topological states were suggested to emerge in photodressed bands under periodic laser driving. Here we propose a viable nonequilibrium route without requiring coherent Floquet states to reach the elusive magnetic Weyl semimetallic phase in pyrochlore iridates by ultrafast modification of the effective electron-electron interaction with short laser pulses. Combining ab initio calculations for a time-dependent self-consistent light-reduced Hubbard U and nonequilibrium magnetism simulations for quantum quenches, we find dynamically modified magnetic order giving rise to transiently emerging Weyl cones that can be probed by time- and angle-resolved photoemission spectroscopy. Our work offers a unique and realistic pathway for nonequilibrium materials engineering beyond Floquet physics to create and sustain Weyl semimetals. This may lead to ultrafast, tens-of-femtoseconds switching protocols for light-engineered Berry curvature in combination with ultrafast magnetism.

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We thank C. Timm for suggesting the pyrochlore iridates as a candidate class of materials to light-induce nontrivial topology beyond Floquet states. Discussions with A. de la Torre are gratefully acknowledged. G.E.T. and M.A.S. acknowledge financial support by the DFG through the Emmy Noether programme (SE 2558/2-1). A.R. acknowledges financial support by the European Research Council (ERC-2015-AdG-694097), and European Union's H2020 program under GA no. 676580 (NOMAD).

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