Programme

P.10 -- Poster

Date: Friday, 24 November 2017

Time: 10:30 - 11:20

Density functional study of the electronic properties of K_x$Fe$_2$Se$_2

Nikki D. Tagdulang (1), Naomi Jane P. Jacosalem (1), Meriam A. Gabule (1), and Leo Cristobal C. Ambolode II (1,2)

(1) Deparment of Physics, Mindanao State University – Iligan Institute of Technology, A. Bonifacio Avenue, 9200 Iligan City, Philippines; (2) Premier Research Institute of Science and Mathematics (PRISM), Mindanao State University – Iligan Institute of Technology, A. Bonifacio Avenue, 9200 Iligan City, Philippines

Angle-resolved photoemission spectroscopy (ARPES) studies reported that the Fermi surface mapping of K_0.8$Fe$_2$Se$_2 shows an electron-like pocket around the Brillouin zone center $\Gamma$ [1]. However, calculations using rigid band model predicted that only hole-like pocket is found around the $\Gamma$ point [2]. It was further shown that the hole-like pocket survives with an increasing Fermi size as the K concentration decreases. To resolve this apparent inconsistency, we calculate the electronic properties of K_x$Fe$_2$Se$_2 using a 2 $\times$ 1 $\times$ 1 supercell. We used PBE-GGA for the exchange correlation potentials with kinetic energy and charge density cut-off of 800 and 6400 eV, respectively. A mesh of 8 $\times$ 8 $\times$ 8 was used for the Brillouin zone integration [3]. We found that the valence band spectra of K_x$Fe$_2$Se$_2 for various K concentrations $x$ = 1.00, 0.75 and 0.50, share similar features. All of the compounds show that Fe-$d$ states dominate the region near the Fermi level. We can also observe the hybridized stats of Fe-$d$ and Se-$p$ orbitals at lower energies. These features are typical for iron-based superconductors. Moreover, for the band structure calculations, only $x$ = 0.75 shows an electron-like band around the $\Gamma$ point, which may correspond to the ARPES results of Zhang, $et al.$ [1]. The electron-like band is mainly dominated by Fe-$d_yz$ orbitals with non-negligible contribution from $d_yz + d_xy$. This result is in concurrence with the experimental work of Chen, $et al.$ [4]. \textbf{References} [1] Y. Zhang, L.X. Yang, M. Xu, Z.R. Ye, F. Chen, C. He, J. Jiang, B.P. Xie, J.J. Ying, X.F. Wang, X.H. Chen, J.P. Hu, D.L. Feng, Nature Materials \textbf{10}, 273-277 (2011). [2] I.R. Shein and A. L. Ivanovskii, Phys. Lett. A \textbf{375}, 1028–1031 (2011). [3] X.W. Yan, M. Gao, Z.Y. Lu, T. Xiang, Phys. Rev. B \textbf{84}, 054502 (2011). [4] F. Chen Q. Ge, M. Xu, $et al.$, Chin. Sci. Bull 57: 3829 (2012).

Presenter: Leo Cristobal C. Ambolode II