Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials

Nature Communications 7, 13940 (2017)

Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials

Hannes Hübener, Michael A. Sentef, Umberto De Giovannini, Alexander F. Kemper, Angel Rubio

Tuning and stabilising topological states, such as Weyl semimetals, Dirac semimetals, or topological insulators, is emerging as one of the major topics in materials science. Periodic driving of many-body systems offers a platform to design Floquet states of matter with tunable electronic properties on ultrafast time scales. Here we show by first principles calculations how femtosecond laser pulses with circularly polarised light can be used to switch between Weyl semimetal, Dirac semimetal, and topological insulator states in a prototypical 3D Dirac material, Na3Bi. Our findings are general and apply to any 3D Dirac semimetal. We establish the concept of timedependent bands and steering of Floquet-Weyl points (Floquet-WPs), and demonstrate how light can enhance topological protection against lattice perturbations. Our work has potential practical implications for the ultrafast switching of materials properties, like optical band gaps or anomalous magnetoresistance. Moreover, we introduce Floquet time-dependent density functional theory (Floquet-TDDFT) as a general and robust first principles method for predictive Floquet engineering of topological states of matter.

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We are grateful to Peizhe Tang for stimulating discussions and a critical reading of our manuscript, and to Ashvin Vishwanath for helpful discussions. We acknowledge financial support from the European Research Council (ERC-2010-AdG-267374), Grupos Consolidados (IT578-13), AFOSR Grant No. FA2386-15-1-0006 AOARD 144088, COST Action MP1306 (EUSpec). H.H. acknowledges support from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7-PEOPLE-2013-IEF project No. 622934. A.F.K. would like to thank the Aspen Center for Physics (supported by National Science Foundation grant PHY-1066293) for their hospitality during part of this work.

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