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arXiv · 1807.08523

Type-II Dirac line node in strained Na3N

Dongwook Kim·Seongjin Ahn·Jong Hyun Jung·Hongki Min·Jisoon Ihm·Jung Hoon Han·Youngkuk Kim
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Abstract

Dirac line node (DLN) semimetals are a class of topological semimetals that feature band-crossing lines in momentum space. We study the type-I and type-II classification of DLN semimetals by developing a criterion that determines the type using band velocities. Using first-principles calculations, we also predict that Na3N under an epitaxial tensile strain realizes a type-II DLN semimetal with vanishing spin-orbit coupling (SOC), characterized by the Berry phase that is Z2-quantized in the presence of inversion and time-reversal symmetries. The surface energy spectrum is calculated to demonstrate the topological phase, and the type-II nature is demonstrated by calculating the band velocities. We also develop a tight-binding model and a low-energy effective Hamiltonian that describe the low-energy electronic structure of strained Na3N. The occurrence of a DLN in Na3N under strain is captured in the optical conductivity, which we propose as a means to experimentally confirm the type-II class of the DLN semimetal.

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Dongwook Kim, Seongjin Ahn, Jong Hyun Jung, Hongki Min, Jisoon Ihm, Jung Hoon Han, Youngkuk Kim. 2018-07-23. Type-II Dirac line node in strained Na3N. https://doi.org/10.1103/physrevmaterials.2.104203

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