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ARPES observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn$_2$As$_2$ and BaMn$_2$Sb$_2$
Authors:
W. -L. Zhang,
P. Richard,
A. van Roekeghem,
S. -M. Nie,
N. Xu,
P. Zhang,
H. Miao,
S. -F. Wu,
J. -X. Yin,
B. B. Fu,
L. -Y. Kong,
T. Qian,
Z. -J. Wang,
Z. Fang,
A. S. Sefat,
S. Biermann,
H. Ding
Abstract:
We performed an angle-resolved photoemission spectroscopy study of BaMn$_2$As$_2$ and BaMn$_2$Sb$_2$, which are isostructural to the parent compound BaFe$_2$As$_2$ of the 122 family of ferropnictide superconductors. We show the existence of a strongly $k_z$-dependent band gap with a minimum at the Brillouin zone center, in agreement with their semiconducting properties. Despite the half-filling of…
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We performed an angle-resolved photoemission spectroscopy study of BaMn$_2$As$_2$ and BaMn$_2$Sb$_2$, which are isostructural to the parent compound BaFe$_2$As$_2$ of the 122 family of ferropnictide superconductors. We show the existence of a strongly $k_z$-dependent band gap with a minimum at the Brillouin zone center, in agreement with their semiconducting properties. Despite the half-filling of the electronic 3$d$ shell, we show that the band structure in these materials is almost not renormalized from the Kohn-Sham bands of density functional theory. Our photon energy dependent study provides evidence for Mn-pnictide hybridization, which may play a role in tuning the electronic correlations in these compounds.
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Submitted 2 November, 2016; v1 submitted 22 August, 2016;
originally announced August 2016.
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Experimental Discovery of the First Nonsymmorphic Topological Insulator KHgSb
Authors:
J. -Z. Ma,
C. -J. Yi,
B. Q. Lv,
Z. J. Wang,
S. -M. Nie,
L. Wang,
L. -Y. Kong,
Y. -B. Huang,
P. Richard,
H. -M. Weng,
B. A. Bernevig,
Y. -G. Shi,
T. Qian,
H. Ding
Abstract:
Topological insulators (TIs) host novel states of quantum matter, distinguished from trivial insulators by the presence of nontrivial conducting boundary states connecting the valence and conduction bulk bands. Up to date, all the TIs discovered experimentally rely on the presence of either time reversal or symmorphic mirror symmetry to protect massless Dirac-like boundary states. Very recently, i…
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Topological insulators (TIs) host novel states of quantum matter, distinguished from trivial insulators by the presence of nontrivial conducting boundary states connecting the valence and conduction bulk bands. Up to date, all the TIs discovered experimentally rely on the presence of either time reversal or symmorphic mirror symmetry to protect massless Dirac-like boundary states. Very recently, it has been theoretically proposed that several materials are a new type of TIs protected by nonsymmorphic symmetry, where glide-mirror can protect novel exotic surface fermions with hourglass-shaped dispersion. However, an experimental confirmation of such new nonsymmorphic TI (NSTI) is still missing. Using angle-resolved photoemission spectroscopy, we reveal that such hourglass topology exists on the (010) surface of crystalline KHgSb while the (001) surface has no boundary state, which is fully consistent with first-principles calculations. We thus experimentally demonstrate that KHgSb is a NSTI hosting hourglass fermions. By expanding the classification of topological insulators, this discovery opens a new direction in the research of nonsymmorphic topological properties of materials.
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Submitted 22 May, 2016;
originally announced May 2016.
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Experimental evidence of large-gap two-dimensional topological insulator on the surface of ZrTe5
Authors:
R. Wu,
J. -Z. Ma,
L. -X. Zhao,
S. -M. Nie,
X. Huang,
J. -X. Yin,
B. -B. Fu,
P. Richard,
G. -F. Chen,
Z. Fang,
X. Dai,
H. -M. Weng,
T. Qian,
H. Ding,
S. H. Pan
Abstract:
Two-dimensional (2D) topological insulators (TIs) with a large bulk band-gap are promising for experimental studies of the quantum spin Hall effect and for spintronic device applications. Despite considerable theoretical efforts in predicting large-gap 2D TI candidates, only few of them have been experimentally verified. Here, by combining scanning tunneling microscopy/spectroscopy and angle-resol…
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Two-dimensional (2D) topological insulators (TIs) with a large bulk band-gap are promising for experimental studies of the quantum spin Hall effect and for spintronic device applications. Despite considerable theoretical efforts in predicting large-gap 2D TI candidates, only few of them have been experimentally verified. Here, by combining scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we reveal that the top monolayer of ZrTe5 crystals hosts a large band gap of ~100 meV on the surface and a finite constant density-of-states within the gap at the step edge. Our first-principles calculations confirm the topologically nontrivial nature of the edge states. These results demonstrate that the top monolayer of ZrTe5 crystals is a large-gap 2D TI suitable for topotronic applications at high temperature.
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Submitted 26 January, 2016;
originally announced January 2016.