Electronic structure of Ca${}_{10}$(Pt${}_{4}$As${}_{8}$)(Fe${}_{2\ensuremath{-}x}$Pt${}_{x}$As${}_{2}$)${}_{5}$ with metallic Pt${}_{4}$As${}_{8}$ layers: An angle-resolved photoemission spectroscopy study

Electronic structure of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ with metallic Pt $_{4}$ As $_{8}$ layers: An angle-resolved photoemission spectroscopy study

X. P. Shen, S. D. Chen, Q. Q. Ge, Z. R. Ye, F. Chen, H. C. Xu, S. Y. Tan, X. H. Niu, Q. Fan, B. P. Xie, and D. L. Feng

Phys. Rev. B 88, 115124 – Published 13 September 2013

Abstract

We studied the low-lying electronic structure of the newly discovered iron-platinum-arsenide superconductor, Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ ( $T_{c} = 22$ K) with angle-resolved photoemission spectroscopy. We found that the Pt $_{4}$ As $_{8}$ layer contributes to a small electronlike Fermi surface, indicative of metallic charge reservoir layers that are rare for iron based superconductors. Moreover, the electronic structure of the FeAs layers resembles those of other prototype iron pnictides to a large extent. However, there is only $d_{x y}$ -orbital originated holelike Fermi surface near the zone center, which is rather strange for an iron pnictide superconductor with relatively high superconducting transition temperature; and the $d_{x z}$ and $d_{y z}$ originated bands are not degenerate at the zone center. Furthermore, all bands near the Fermi energy show negligible $k_{z}$ dependence, indicating the strong two-dimensional nature of this material. Our results indicate this material possesses a rather interesting electronic structure, which enriches our current knowledge of iron based superconductors.

Received 8 August 2013

DOI:https://doi.org/10.1103/PhysRevB.88.115124

Authors & Affiliations

X. P. Shen¹, S. D. Chen¹, Q. Q. Ge¹, Z. R. Ye¹, F. Chen², H. C. Xu¹, S. Y. Tan¹, X. H. Niu¹, Q. Fan¹, B. P. Xie¹, and D. L. Feng^1,*

¹State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
²Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China

^*dlfeng@fudan.edu.cn

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Vol. 88, Iss. 11 — 15 September 2013

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Figure 1
The crystallographic and superconducting properties of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . (a) Powder XRD pattern of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2}$ As $_{2}$ ) $_{5}$ . The powder was obtained by grinding the single crystals. The inset is a schematic picture of the crystal structure of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2}$ As $_{2}$ ) $_{5}$ . (b) Top view of Pt $_{4}$ As $_{8}$ and FeAs layers. (c) The low-energy electron diffraction pattern of a Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ single crystal. Reflection peaks from both FeAs (blue circles) and Pt $_{4}$ As $_{8}$ (red circles) lattices are observed. (d) The magnetic susceptibility of an as-grown Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ single crystal taken at a magnetic field of 20 Oe in the zero-field cool mode, and its resistivity as a function of temperature.Reuse & Permissions
Figure 2
Photoemission data of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . (a) Schematic of two polarization geometries of experimental setups, reproduced from Ref. 24. (b) Sketch of Fermi surface for Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . (c) Photoemission intensity map at the Fermi energy ( $E_{F}$ ) integrated over [ $E_{F} - 10$ meV, $E_{F} + 10$ meV] in $p$ polarization. The 2D Brillouin zone in blue is for the FeAs layer and the dashed one in red is for the PtAs layer. (e) Photoemission intensity along (0, 0)-( $π$ , 0) direction, as indicated by the green arrow in panel (a). The solid lines indicate the bands dispersions extracted from the corresponding MDC's. (g) The second derivative with respect to energy of the data in panel (a). (d), (f), and (h) are the same as in panels (c), (e), and (g), respectively, but taken in $s$ polarization. (i) Summary of the experimental band structure for Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . All data were taken with 26 eV photons at UVSOR.Reuse & Permissions
Figure 3
Photoemission data of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . (a) Photoemission intensity map at $E_{F}$ integrated over [ $E_{F} - 30$ meV, $E_{F} + 30$ meV]. The small electron pockets are enclosed by the dashed circles. (b) Photoemission intensity plots of cuts #1-#16 as indicated in panel (a). The positions of the small electron pockets are marked by the arrows. All data were taken with randomly polarized 21.2 eV photons from a helium discharge lamp.Reuse & Permissions
Figure 4
The Fermi surface and band structure as a function of $k_{z}$ for Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ . (a) Photoemission intensity map in the $k_{x}$ - $k_{z}$ plane in $p$ polarization. (b) The photoemission intensity with typical photon energies along the cuts #1 and #2 in panel (a). (c) The corresponding MDC's at $E_{F}$ with different photon energies in panel (a), the peaks indicating Fermi crossing $k_{F}$ are marked by red solid triangles. (d) and (e) are the same as in panels (a) and (b), respectively, but in $s$ polarization. (f) is the same as in panel (d), but taken at low photon energies from 22 to 38 eV for a better momentum resolution. Different $k_{z}^{'}$ s were accessed by varying the photon energies at Beamline of SLS and Beamline 7U of UVSOR, as indicated by the blue lines, where an inner potential of 13 eV is used to obtain $k_{z}$ . The data in panels (a)–(e) and panel (f) were collected at SLS and UVSOR, respectively.Reuse & Permissions

Physical Review B

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Electronic structure of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ with metallic Pt $_{4}$ As $_{8}$ layers: An angle-resolved photoemission spectroscopy study

X. P. Shen, S. D. Chen, Q. Q. Ge, Z. R. Ye, F. Chen, H. C. Xu, S. Y. Tan, X. H. Niu, Q. Fan, B. P. Xie, and D. L. Feng

Phys. Rev. B 88, 115124 – Published 13 September 2013

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Physical Review B

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Electronic structure of Ca10(Pt4As8)(Fe2−xPtxAs2)5 with metallic Pt4As8 layers: An angle-resolved photoemission spectroscopy study

X. P. Shen, S. D. Chen, Q. Q. Ge, Z. R. Ye, F. Chen, H. C. Xu, S. Y. Tan, X. H. Niu, Q. Fan, B. P. Xie, and D. L. Feng

Phys. Rev. B 88, 115124 – Published 13 September 2013

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Electronic structure of Ca $_{10}$ (Pt $_{4}$ As $_{8}$ )(Fe $_{2 - x}$ Pt $_{x}$ As $_{2}$ ) $_{5}$ with metallic Pt $_{4}$ As $_{8}$ layers: An angle-resolved photoemission spectroscopy study