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Evidence for strong non-local correlation effects in iridates : Sr2IrO4 and Ba2IrO4

Cyril Martins, LCPQ (Toulouse)

Séminaire LCPQ

Salle 20 RdC

Jeudi 4 Décembre 2014, 14h-15h

The observed physical properties of iridium-based oxides – or iridates – are the consequences of a subtle interplay of the spin-orbit coupling, the local crystal field and the Coulomb interactions between electrons. Strontium iridate (Sr2IrO4) and baryum iridate (Ba2IrO4) are two striking examples where this cooperative effect even drives these compounds insulating, with one hole in the t2g manifold of projected jeff=1/2 total angular momentum.

Whereas their low-temperature phase (below 230-240 K) exhibits a non-collinear magnetic order, the high-temperature phase is paramagnetic while still insulating [1,2]. This situation has been rationalized for Sr2IrO4 by combining density functional theory within the local density approximation and dynamical mean field theory (LDA+DMFT) : indeed, this calculation evidences the experimentally observed reduction of effective degeneracy of the system within an ab initio picture [3].

In this work, we discuss the role of non-local correlation effects in these two layered iridates and address its consequence on their electronic structure. Using state-of-the-art constrained random-phase techniques as well as a cluster extension of LDA+DMFT, we calculate momentum-resolved spectral functions compared to angle-resolved photoemission spectra [4].

[1] B. J. Kim et al., Phys. Rev. Lett. 101, 076402 (2008).

[2] S. Moser et al., New J. Phys. 16, 013008 (2014).

[3] C. Martins, M. Aichhorn, L. Vaugier, S. Biermann, Phys. Rev. Lett. 107, 266404 (2011).

[4] C Martins, L. Perfetti, S. Biermann, to be published.