Jans Henke, Felix Flicker, Jude Laverock, Jasper van Wezel
SciPost Phys. 9, 056 (2020) ·
published 21 October 2020
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Charge order -- ubiquitous among correlated materials -- is customarily described
purely as an instability of the electronic structure. However, the resulting
theoretical predictions often do not match high-resolution experimental data. A
pertinent case is $1T$-VSe$_2$, whose single-band Fermi surface and
weak-coupling nature make it qualitatively similar to the Peierls model
underlying the traditional approach. Despite this, its Fermi surface is poorly
nested, the thermal evolution of its charge density wave (CDW) ordering vectors
displays an unexpected jump, and the CDW gap itself evades detection in direct
probes of the electronic structure. We demonstrate that the thermal variation
of the CDW vectors is naturally reproduced by the electronic susceptibility
when incorporating a structured, momentum-dependent electron-phonon coupling,
while the evasive CDW gap presents itself as a localized suppression of
spectral weight centered above the Fermi level. Our results showcase the
general utility of incorporating a structured coupling in the description of
charge ordered materials, including those that appear unconventional.
S. V. Ramankutty, J. Henke, A. Schiphorst, R. Nutakki, S. Bron, G. Araizi-Kanoutas, 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 non-symmorphic crystal symmetries that could protect
band crossings, offering the possibility of a quasi-2D, robust Dirac semi-metal
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 Y-states) around the (0,$\pi$/a)-point in
$k$-space. The ARPES Fermi surface agrees perfectly with that from
bulk-sensitive 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 Y-states to be gapped above E$_F$,
suggesting trivial topology. Subsequent analysis within both theory approaches
shows the Berry phase to be zero, indicating the non-topological character of
the transport in SrMnSb$_2$, a conclusion backed up by the analysis of the
quantum oscillation data from our crystals.
Ms Henke: "Dear referee, We would like t..."
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