Fig. 1: Structural and electronic features exhibited by ruthenates A2RuO4.
From: Orbital-order as the driving mechanism for superconductivity in ruthenates
a Crystallographic structure exhibited by n = 1 undistorted Ruddlesden-Popper phase. The undistorted cell adopts an I4/mmm symmetry based on ABO3 perovskite building blocks stacked along c and separated by one AO layer. b Jahn-Teller distortion for one ABO3 layer, corresponding to a Q2 mode, producing a contraction and elongation of two B-O bond lengths with alternating contraction/expansion on nearest neighbor B sites. c–e Ru d states splitting according to O6 octahedral deformations for totally undistorted O6 groups (c), compressed (d), or extended (e). The distortion is determined by the co and ao ratios defined in (a). ∆CFo and ∆ex are octahedral crystal fields and exchange splitting, respectively. Majority (minority) spin channel is represented in blue (red). The point group symmetry for the undistorted octahedral situation is Oh, that can be lowered to D2h by a co/ao ≠ 1 and produce an additional ∆CF’ splitting.
