期刊
NATURE COMMUNICATIONS
卷 12, 期 1, 页码 -出版社
NATURE PORTFOLIO
DOI: 10.1038/s41467-021-23727-3
关键词
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资金
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [258499086-SFB 1170]
- Wurzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter -ct.qmat [390858490-EXC 2147, RE1469/13-1]
- Federal Ministry of Education and Research (BMBF) [05KS7FK2, 05K10FK1, 05K12FK1, 05K13FK1, 05KS7WW1, 05K10WW2]
- European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant [897276]
- Gauss Centre for Supercomputing e.V.
- National Research Foundation [NSF DMR-1606952]
- National Science Foundation, Division of Materials Research [DMR-1644779]
- state of Florida
- University of Wurzburg
- Marie Curie Actions (MSCA) [897276] Funding Source: Marie Curie Actions (MSCA)
The study reports momentum-resolved spectroscopic signatures of Berry flux monopoles in TaAs, providing a basis for the study of quantum-geometric effects in solids. The experimental results show topologically non-trivial winding of orbital-angular-momentum and chirality-dependent spin-angular-momentum in Weyl semimetals, indicating the presence of Berry flux monopoles.
Since the early days of Dirac flux quantization, magnetic monopoles have been sought after as a potential corollary of quantized electric charge. As opposed to magnetic monopoles embedded into the theory of electromagnetism, Weyl semimetals (WSM) exhibit Berry flux monopoles in reciprocal parameter space. As a function of crystal momentum, such monopoles locate at the crossing point of spin-polarized bands forming the Weyl cone. Here, we report momentum-resolved spectroscopic signatures of Berry flux monopoles in TaAs as a paradigmatic WSM. We carried out angle-resolved photoelectron spectroscopy at bulk-sensitive soft X-ray energies (SX-ARPES) combined with photoelectron spin detection and circular dichroism. The experiments reveal large spin- and orbital-angular-momentum (SAM and OAM) polarizations of the Weyl-fermion states, resulting from the broken crystalline inversion symmetry in TaAs. Supported by first-principles calculations, our measurements image signatures of a topologically non-trivial winding of the OAM at the Weyl nodes and unveil a chirality-dependent SAM of the Weyl bands. Our results provide directly bulk-sensitive spectroscopic support for the non-trivial band topology in the WSM TaAs, promising to have profound implications for the study of quantum-geometric effects in solids. Weyl semimetals exhibit Berry flux monopoles in momentum-space, but direct experimental evidence has remained elusive. Here, the authors reveal topologically non-trivial winding of the orbital-angular-momentum at the Weyl nodes and a chirality-dependent spin-angular-momentum of the Weyl bands, as a direct signature of the Berry flux monopoles in TaAs.
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