Abstract
The chirality of chiral multifold fermions in reciprocal space is related to the chirality of crystal lattice structures in real space. In this study, we propose a strategy to detect and identify multifold fermions of opposite chirality in nonmagnetic systems using second-order optical transports. Chiral crystals related with inversion operations cannot be made to overlap with each other via any experimental operation. Further, chiral multifold fermions within such crystals host opposite chiralities corresponding to a given $k$ point. A change in chirality is indicated by a corresponding change in the sign of the second-order charge current dominated by chiral fermions. This property can be exploited to study the relationship between chiralities in reciprocal and real spaces by utilizing bulk transport.
Highlights
AND INTRODUCTIONMultifold massless fermions with nonzero topological charge have garnered significant attention in the field of topological materials
Since multifold fermions are located at high-symmetry points, they guarantee long surface Fermi arcs spanning the entire Brillouin zone (BZ) [3,4,5,6]
Long Fermi arcs, high-order degenerated band crossings, and topological circular photogalvanic effects (CPGE) were soon observed in the expected chiral crystals via angle-resolved photoemission spectroscopty (ARPES) [9,10,11,12,13], scanning tunneling microscopy (STM) [14], and optical measurements [15,16,17]
Summary
Multifold massless fermions with nonzero topological charge have garnered significant attention in the field of topological materials. In addition to the wide separation between opposite topological charges in the momentum space, the absence of mirror symmetry leads to their large separation in energy space, providing an ideal platform for the study of quantized circular photogalvanic effects (CPGE) [3,5,7,8] Following their theoretical predictions, long Fermi arcs, high-order degenerated band crossings, and topological CPGE were soon observed in the expected chiral crystals via angle-resolved photoemission spectroscopty (ARPES) [9,10,11,12,13], scanning tunneling microscopy (STM) [14], and optical measurements [15,16,17]. Chiral crystals in the space group P213 with opposite chiralities are related via a simple inversion operation, as depicted in Fig. 1(a) and 1(b). The second-order responses are odd with respect to inversion, which suggests a possible method to detect the sign change in chirality
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