Eur. Phys. J. B (2015) 88: 101
https://doi.org/10.1140/epjb/e2015-60044-3

Regular Article

Orbital ordering transition in the single-layer manganites near half doping: a weak-coupling approach

¹ Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea
² Department of Physics, Hanyang University, 17 Haengdang, Seongdong, Seoul 133-791, Korea

^a e-mail: dheeraj80@hanyang.ac.kr

Received: 14 January 2015
Received in final form: 18 February 2015
Published online: 15 April 2015

Abstract

The roles of crystal-field splitting and Jahn-Teller distortions on the orbital ordering transition are investigated in the single-layer manganites near half doping. Crystal-field splitting of energy levels favoring the d_{3z² − r²} occupancy provides not only the correct Fermi surface topology for La_0.5Sr_1.5MnO₄ having a circular electron pocket around the Γ point, but also enhances the flatness of the hole pocket around the M point thereby improving the nesting. In the presence of the circular electron pocket, Jahn-Teller distortions are found to be crucial for the transition to the transverse orbital ordering with ordering wavevector (0.5π,0.5π). In the hole-doping regime 0.5 ≤ x ≤ 0.7, the orbital ordering wavevector shows a linear dependence on the hole concentration in accordance with the experiments.