A study led by Baojie Feng of the Hiroshima Synchrotron Radiation Center reports the discovery of two-dimensional Dirac nodal lines in monolayer Cu₂Si. Monolayer Cu₂Si is composed of a honeycomb lattice of copper atoms and a hexagonal lattice of Si atoms. Although this material has been synthesized decades ago, Feng and his collaborators improved the growth methods and synthesized high-quality samples. By using angle-resolved photoemission spectroscopy, they examined the electronic structures of Cu₂Si monolayer in detail, and discovered two Dirac nodal lines. They have done extensive theoretical calculations and concluded that the crystalline symmetry in Cu₂Si protects the two Dirac nodal lines against external perturbations, making it a promising material in designing high-speed quantum devices.

• Title: Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu₂Si
• Authors: Baojie Feng, Botao Fu, Shusuke Kasamatsu, Suguru Ito, Peng Cheng, Cheng-Cheng Liu, Ya Feng, Shilong Wu, Sanjoy K. Mahatha, Polina Sheverdyaeva, Paolo Moras, Masashi Arita, Osamu Sugino, Tai-Chang Chiang, Kenya Shimada, Koji Miyamoto, Taichi Okuda, Kehui Wu, Lan Chen, Yugui Yao, and Iwao Matsuda
• Journal: Nature Communications
• DOI: 10.1038/s41467-017-01108-z

By Margaux Phares