S. V. Ramankutty, J. Henke, A. Schiphorst, R. Nutakki, S. Bron, G. AraiziKanoutas, S. K. Mishra, Lei Li, Y. K. Huang, T. K. Kim, M. Hoesch, C. Schlueter, T. L. Lee, A. de Visser, Zhicheng Zhong, Jasper van Wezel, E. van Heumen, M. S. Golden
SciPost Phys. 4, 010 (2018) ·
published 21 February 2018

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SrMnSb$_2$ is suggested to be a magnetic topological semimetal. It contains
square, 2D Sb planes with nonsymmorphic crystal symmetries that could protect
band crossings, offering the possibility of a quasi2D, robust Dirac semimetal
in the form of a stable, bulk (3D) crystal. Here, we report a combined and
comprehensive experimental and theoretical investigation of the electronic
structure of SrMnSb$_2$, including the first ARPES data on this compound.
SrMnSb$_2$ possesses a small Fermi surface originating from highly 2D, sharp
and linearly dispersing bands (the Ystates) around the (0,$\pi$/a)point in
$k$space. The ARPES Fermi surface agrees perfectly with that from
bulksensitive Shubnikov de Haas data from the same crystals, proving the
Y$$states to be responsible for electrical conductivity in SrMnSb$_2$. DFT and
tight binding (TB) methods are used to model the electronic states, and both
show good agreement with the ARPES data. Despite the great promise of the
latter, both theory approaches show the Ystates to be gapped above E$_F$,
suggesting trivial topology. Subsequent analysis within both theory approaches
shows the Berry phase to be zero, indicating the nontopological character of
the transport in SrMnSb$_2$, a conclusion backed up by the analysis of the
quantum oscillation data from our crystals.