Phys. Rev. B 103, 245104 (2021) - Electronic structure examination of the topological properties of ${\mathrm{CaMnSb}}_{2}$ by angle-resolved photoemission spectroscopy

Electronic structure examination of the topological properties of ${CaMnSb}_{2}$ by angle-resolved photoemission spectroscopy

Hongtao Rong, Liqin Zhou, Junbao He, Chunyao Song, Jianwei Huang, Cheng Hu, Yu Xu, Yongqing Cai, Hao Chen, Cong Li, Qingyan Wang, Lin Zhao, Zhihai Zhu, Guodong Liu, Zuyan Xu, Genfu Chen, Hongming Weng, and X. J. Zhou

Phys. Rev. B 103, 245104 – Published 1 June 2021

Abstract

We have carried out detailed high-resolution angle-resolved photoemission spectroscopy measurements and band structure calculations to study the electronic structure of $Ca Mn {Sb}_{2}$ . The observed Fermi surface mainly consists of one hole pocket around the $Γ$ point and one tiny hole pocket at the $Y$ point. Strong spectral weight accumulation along the $Γ - X$ direction is observed on the holelike Fermi surface around the $Γ$ point, suggesting strong anisotropy of the density of states along the Fermi surface. The tiny hole pocket at the $Y$ point originates from an anisotropic Dirac-like band with the crossing point of the linear bands lying $\sim 10$ meV above the Fermi level. These observations are in good agreement with the band structure calculations. In addition, we observe additional features along the $Γ - Y$ line that cannot be accounted for by the band structure calculations. Our results provide important information in the understanding and exploration of novel properties in $Ca Mn {Sb}_{2}$ and related materials.

Received 9 March 2021
Accepted 12 May 2021

DOI:https://doi.org/10.1103/PhysRevB.103.245104

Physics Subject Headings (PhySH)

Electronic structure Fermi surface Topological materials

Angle-resolved photoemission spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Hongtao Rong^1,2, Liqin Zhou^1,2, Junbao He ^1,2,3, Chunyao Song^1,2, Jianwei Huang^1,2, Cheng Hu ^1,2, Yu Xu^1,2, Yongqing Cai^1,2, Hao Chen^1,2, Cong Li^1,2, Qingyan Wang^1,2, Lin Zhao^1,2,4, Zhihai Zhu^1,2, Guodong Liu^1,2,4, Zuyan Xu⁵, Genfu Chen^1,2, Hongming Weng^1,2, and X. J. Zhou ^1,2,4,6,*

¹National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
²University of Chinese Academy of Sciences, Beijing 100049, China
³Henan International Joint Laboratory of MXene Materials Microstructure, College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, China
⁴Songshan Lake Materials Laboratory, Dongguan 523808, China
⁵Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
⁶Beijing Academy of Quantum Information Sciences, Beijing 100193, China

^*Corresponding author: xjzhou@aphy.iphy.ac.cn

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Vol. 103, Iss. 24 — 15 June 2021

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Figure 1
Crystal structure and calculated band structures of $Ca Mn {Sb}_{2}$ . (a) Crystal structure of $Ca Mn {Sb}_{2}$ . The unit cell is indicated by black lines. It crystalizes in an orthorhombic structure (space group: $P n m a$ ) with lattice constants $a = 22.09$ Å, $b = 4.32$ Å, and $c = 4.35$ Å. (b) Top view of the central Sb layer, which consists of a zigzag chainlike structure along the $b$ axis. (c) Three-dimensional Brillouin zone of $Ca Mn {Sb}_{2}$ . Green lines indicate high-symmetry directions. (d) and (e) Calculated band structure of $Ca Mn {Sb}_{2}$ (d) without and (e) with spin-orbit coupling at $k_{z} = 0$ . (f) Calculated band structure of $Ca Mn {Sb}_{2}$ by considering spin-orbit coupling and the mBJ potential at $k_{z} = 0$ . The bands near the Fermi level originate mainly from the Sb $5 p_{x}$ (red circles), $5 p_{y}$ (green squares), and $5 p_{z}$ (blue diamonds) orbitals. Calculated band structure of $Ca Mn {Sb}_{2}$ by considering spin-orbit coupling and mBJ potential at(g) $k_{z} = 0$ and (h) $k_{z} = π / a$ .
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Figure 2
Measured and calculated Fermi surface mapping and constant-energy contours of $Ca Mn {Sb}_{2}$ . (a) Constant-energy contours of $Ca Mn {Sb}_{2}$ at binding energies of 0, 100, 200, and 300 meV measured at 30 K with a 21.218 eV helium lamp. The major E vector is along $k_{y}$ direction, as marked by the arrow at the bottom-left inset of the left-most panel. (b) Same as (a). The major $E$ vector is along the $k_{x}$ direction, as marked by the arrow at the bottom left inset in the leftmost panel. All constant-energy contours in (a) and (b) are obtained by integrating the photoemission spectral weight over a $[- 20, 20]$ meV energy window with respect to the corresponding binding energy. The first Brillouin zone is indicated by the black squares. (c) Calculated constant-energy contours at binding energies of 0, 100, 200, and 300 meV for $k_{z} = 0$ . An experimental Fermi level, $E_{F (e x p)}$ , is taken which is 0.12 eV below the Fermi level in the calculation, as shown in Fig. 1.
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Figure 3
Dirac-cone-like structure around the $Y$ point in $Ca Mn {Sb}_{2}$ measured with 21.218 eV photon energy at 30 K. (a) The second-derivative constant-energy contours around the $Y$ point obtained by integrating the photoemission spectral weight over a $[- 20, 20]$ meV energy window with respect to binding energies of 0, 50, 100, 150, 200, and 250 meV. (b) Band structure measured along various momentum cuts. The locations of the momentum cuts, cut 1 to cut 9, are marked by black lines in the leftmost panel of (a). (c) Detailed band structure taken along momentum cut 5 that is along the $Y M$ direction crossing the $Y$ point. (d) Momentum distribution curves (MDCs) of the photoemission image in (c) at different binding energies. (e) Photoemission spectra (energy dispersion curves, EDCs) at different momenta from photoemission image in (c). The blue line represents the EDC at the $Y$ point [marked by the blue arrow and $k_{T}$ in (c)]. (f) Band structure taken along momentum cut 10. The location of cut 10 is marked by the red line in the leftmost panel in (a) that crosses the $Y$ point. The image is the second derivative of the original data with respect to the momentum. (g) Three-dimensional schematic of the Dirac-cone-like structure at the $Y$ point.
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Figure 4
Detailed holelike Fermi surface and band structures of $Ca Mn {Sb}_{2}$ around the $Γ$ point measured at 30 K. (a) Fermi surface mapping measured with a 6.994 eV laser by integrating the photoemission spectral weight over a $[- 10, 10]$ meV energy window. The $E$ vector is along the $k_{x}$ direction, as marked by the arrow in the bottom left corner. (b) Same as (a), but the $E$ vector is along the $k_{y}$ direction, as marked by the arrow in the bottom left corner. (c) Band structure measured along various momentum cuts; the locations of the momentum cuts are marked by black lines in (a). (d) MDCs at the Fermi level from the bands in (c) measured along various momentum cuts. (e) The angle-dependent MDC peak height along the Fermi surface in (a) (blue line) and (b) (red line) as a function of the Fermi surface angle. The Fermi surface angle $θ$ is defined in the inset. The entire holelike Fermi pocket is composed of the Sb $p_{x}$ orbital. (f) EDCs at different momenta from the cut 1 photoemission image [leftmost panel in (c)]. The EDCs at the Fermi momenta on the left side ( $k_{F L}$ ) and right side ( $k_{F R}$ ) of the band and at the $Γ$ point ( $k_{F C}$ ) are marked by blue lines.
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Figure 5
Detailed electronic structure of $Ca Mn {Sb}_{2}$ around the $Γ$ point measured at 30 K. Constant-energy contours around $Γ$ obtained by integrating the photoemission spectral weight over a $[- 10, 10]$ meV energy window with respect to (a) 0 eV, (b) 0.1 eV, and (c) 0.2 eV binding energies. The data are the same as in Fig. 4 measured with a 6.994 eV laser, and the $E$ vector is along the $k_{x}$ direction, as marked by the arrow in the inset in (a). (d) Band structure measured along various momentum cuts; the locations of the momentum cuts are marked by black lines in (a). (e) MDCs at the different binding energies from the bands in (d) measured along various momentum cuts. (f) The corresponding second-derivative images with respect to the momentum of the band structures in (d). (g) Band structure measured with a 21.218 eV helium lamp along the horizontal $Γ - X$ direction [the same as cut 3 marked by the black line in (a)]. (h) MDCs at the different binding energies from the band structure in (g). (i) The corresponding second-derivative image with respect to momentum of the band structure in (g). (j) DFT-projected bulk bands and surface bands of the Sb-terminated (100) surface along the $Y - Γ - X$ directions.
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Figure 6
Summary of crystal structures and electronic structures of $A Mn P_{2}$ ( $A$ =Ca, Sr, Ba, Eu, Yb; $P$ =Sb, Bi). Four kinds of crystal structures are identified with $Ca Mn {Bi}_{2}$ [50], $Yb Mn {Bi}_{2}$ [56], and $Yb Mn {Sb}_{2}$ [73] crystalized in the $P 4 / n m m$ space group; $Sr Mn {Bi}_{2}$ [47, 50], $Ba Mn {Bi}_{2}$ [75], and $Eu Mn {Bi}_{2}$ [56] in the $I 4 / m m m$ space group; $Ba Mn {Sb}_{2}$ [59, 72] in the $I 2 m m$ space group; and $Ca Mn {Sb}_{2}$ , $Sr Mn {Sb}_{2}$ , [71] and $Eu Mn {Sb}_{2}$ [76] in the $P n m a$ space group. The representative measured Fermi surface mapping for each compound is displayed.
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Physical Review B

covering condensed matter and materials physics

Electronic structure examination of the topological properties of ${CaMnSb}_{2}$ by angle-resolved photoemission spectroscopy

Hongtao Rong, Liqin Zhou, Junbao He, Chunyao Song, Jianwei Huang, Cheng Hu, Yu Xu, Yongqing Cai, Hao Chen, Cong Li, Qingyan Wang, Lin Zhao, Zhihai Zhu, Guodong Liu, Zuyan Xu, Genfu Chen, Hongming Weng, and X. J. Zhou

Phys. Rev. B 103, 245104 – Published 1 June 2021

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Physical Review B

covering condensed matter and materials physics

Electronic structure examination of the topological properties of CaMnSb2 by angle-resolved photoemission spectroscopy

Hongtao Rong, Liqin Zhou, Junbao He, Chunyao Song, Jianwei Huang, Cheng Hu, Yu Xu, Yongqing Cai, Hao Chen, Cong Li, Qingyan Wang, Lin Zhao, Zhihai Zhu, Guodong Liu, Zuyan Xu, Genfu Chen, Hongming Weng, and X. J. Zhou

Phys. Rev. B 103, 245104 – Published 1 June 2021

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Electronic structure examination of the topological properties of ${CaMnSb}_{2}$ by angle-resolved photoemission spectroscopy