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Dirac Fermions in Antiferromagnetic FeSn Kagome Lattices with Combined Space Inversion and Time Reversal Symmetry | | Zhiyong Lin
; Chongze Wang
; Pengdong Wang
; Seho Yi
; Lin Li
; Qiang Zhang
; Yifan Wang
; Zhongyi Wang
; Yan Sun
; Zhe Sun
; Jun-Hyung Cho
; Changgan Zeng
; Zhenyu Zhang
; | | Date: |
13 Jun 2019 | | Abstract: | Symmetry principles play a critical role in formulating the fundamental laws
of nature$^{1}$, with a large number of symmetry-protected topological states
identified in recent studies of quantum materials$^{2,3}$. As compelling
examples, massless Dirac fermions are jointly protected by the space inversion
symmetry $P$ and time reversal symmetry $T$ supplemented by additional
crystalline symmetry$^{4-8}$, while evolving into Weyl fermions when either $P$
or $T$ is broken$^{4,9-11}$. Strikingly, such massless Dirac fermions are
expected to survive when each of the $P$ and $T$ symmetries is individually
broken but the combined $PT$ symmetry is preserved$^{12}$. To date, this
conceptually intriguing prediction remains to be experimentally validated.
Here, based on angle-resolved photoemission spectroscopy (ARPES) aided by
first-principles calculations, we present the first experimental observation of
massless Dirac fermions in a layered FeSn crystal containing
antiferromagnetically coupled ferromagnetic Fe kagome layers. In this system,
each of the $P$ and $T$ symmetries is individually broken, but the stable Dirac
points are protected by the combined $PT$ symmetry with additional
non-symmorphic $S_{2z}$ symmetry. We further demonstrate that by breaking the
$PT$ or $S_{2z}$ symmetry, we can transform the massless Dirac fermions into
massless Weyl or massive Dirac fermions. The present study substantially
enriches our fundamental understanding of the intricate connections between
symmetries and topologies of matter, especially with the spin degree of freedom
playing a vital role. | | Source: | arXiv, 1906.5755 | | Services: | Forum | Review | PDF | Favorites | |
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