Helicity-dependent photocurrents in the chiral Weyl semimetal RhSi

Dylan Rees; Kaustuv Manna; Baozhu Lu; Takahiro Morimoto; Horst Borrmann; Claudia Felser; J E Moore; Darius H Torchinsky; J Orenstein

doi:10.1126/sciadv.aba0509

Helicity-dependent photocurrents in the chiral Weyl semimetal RhSi

Sci Adv. 2020 Jul 15;6(29):eaba0509. doi: 10.1126/sciadv.aba0509. eCollection 2020 Jul.

Authors

Dylan Rees^{1

2}, Kaustuv Manna³, Baozhu Lu⁴, Takahiro Morimoto^{1

5}, Horst Borrmann³, Claudia Felser³, J E Moore^{1

2}, Darius H Torchinsky⁴, J Orenstein^{1

2}

Affiliations

¹ Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA.
² Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
³ Max Planck Institute for Chemical Physics of Solids, Dresden D-01187, Germany.
⁴ Department of Physics, Temple University, Philadelphia, PA 19122, USA.
⁵ Department of Applied Physics, The University of Tokyo, Hongo, Tokyo 113-8656, Japan.

Abstract

Weyl semimetals are crystals in which electron bands cross at isolated points in momentum space. Associated with each crossing point (or Weyl node) is a topological invariant known as the Berry monopole charge. The circular photogalvanic effect (CPGE), whereby circular polarized light generates a helicity-dependent photocurrent, is a notable example of a macroscopic property that emerges directly from the topology of the Weyl semimetal band structure. Recently, it was predicted that the amplitude of the CPGE associated with optical transitions near a Weyl node is proportional to its monopole charge. In chiral Weyl systems, nodes of opposite charge are nondegenerate, opening a window of wavelengths where the CPGE resulting from uncompensated Berry charge can emerge. Here, we report measurements of CPGE in the chiral Weyl semimetal RhSi, revealing a CPGE response in an energy window that closes at 0.65 eV, in agreement with the predictions of density functional theory.

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