Direct optical detection of Weyl fermion chirality in a topological semimetal

By Q. Ma, Su-Yang Xu, Ching-Kit Chan, Chenglong Zhang, G. Chang, Y. Lin, W. Xie, Tomás Palacios, Hsin Lin, S. Jia and 3 more. Nature Physics, 2017

397 citations recorded by the source corpus.

Measuring the photocurrent response to circularly polarized mid-infrared light provides direct access to the chirality of Weyl fermions in Weyl semimetals — the property responsible for a range of exotic phenomena. A Weyl semimetal is a novel topological phase of matter1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16, in which Weyl fermions arise as pseudo-magnetic monopoles in its momentum space. The chirality of the Weyl fermions, given by the sign of the monopole charge, is central to the Weyl physics, since it directly serves as the sign of the topological number5,15 and gives rise to exotic properties such as Fermi arcs5,9,12 and the chiral anomaly15,16,17,18,19. Here, we directly detect the chirality of the Weyl fermions by measuring the photocurrent in response to circularly polarized mid-infrared light. The resulting photocurrent is determined by both the chirality of Weyl fermions and that of the photons. Our results pave the way for realizing a wide range of theoretical proposals15,16,20,21,22,23,24,25,26,27,28,29,30 for studying and controlling the Weyl fermions and their associated quantum anomalies by optical and electrical means. More broadly, the two chiralities, analogous to the two valleys in two-dimensional materials31,32, lead to a new degree of freedom in a three-dimensional crystal with potential novel pathways to store and carry information.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/4abf32db1aa30ae53d1969582f0a3e38428c9ada

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Citations in the corpus

Topological Semimetals from First Principles (2018, background): “The breaking of P symmetry in nonmagnetic Weyl semimetals suggests that they may have interesting nonlinear optical properties, such as second harmonic generation and shift current, and these nonlinear optical responses have recently attracted much recent attention (106, 107, 108, 109, 110, 111).”
Weyl and Dirac semimetals in three-dimensional solids (2017, background): “There has been recent claim to have observed such triply degenerate points in MoP (Lv et al., 2017) and in tungsten carbide WC (Ma et al., 2017).”