Importance of effective dimensionality in manganese pnictides

Abstract

In this paper we investigate the two manganese pnictides BaMn$_2$As$_2$ and LaMnAsO, using fully charge self-consistent density functional plus dynamical mean-field theory calculations. These systems have a nominally half-filled d shell, and as a consequence, electronic correlations are strong, placing these compounds at the verge of a metal-insulator transition. Although their crystal structure is composed of similar building blocks, our analysis shows that the two materials exhibit a very different effective dimensionality, LaMnAsO being a quasi-two-dimensional material in contrast to the much more three-dimensional BaMn$_2$As$_2$. We demonstrate that the experimentally observed differences in the N\'eel temperature, the band gap, and the optical properties of the manganese compounds under consideration can be traced back to exactly this effective dimensionality. Our calculations show excellent agreement with measured optical spectra.Comment: 9 pages, 9 figure

Angle-resolved photoemission observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn2As2 and BaMn2Sb2Zhang1, Richard2, Roekeghem3 et al. 2016Phys. Rev. B234270View full textAdd to dashboardCite

“…A recent study shows that density functional theory (DFT) calculations, which do not include the effect of the electronic correlations, give results that are quite different from the spectral function calculated by DFT+dynamical mean field theory (DFT+DMFT) in the paramagnetic state of LaOMnAs [32], thus expressing the effect of the electronic correlations. It is also argued that the proximity to a Mott transition in LaOMnAs and BaMn 2 As 2 is responsible for their high Néel temperatures T N 's [32]. For example, BaMn 2 As 2 exhibits G-type antiferromagnetism with a Néel temperature as high as T N = 625 K and a large ordered moment (µ = 3.9µ B ) [17].…”

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“…ARPES study [39] and DFT+DMFT calculations [40] have shown that the valence band of BaMn 2 As 2 mainly consists of Mn 3d x 2 −y 2 and As 4p z orbitals. The doped holes occupy the hybridized d-p orbital, whose wave function is obtained by the LCAO method, |ψ dp ,…”

“…For this purpose, we introduce a tight-binding Hamiltonian for the valence band of BaMn 2 As 2 mainly consisting of Mn d x 2 −y 2 orbital [39,40].…”

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“…(This energy scale is significantly lower than the resonance mode energy employed in most of the strong coupling simulations mentioned above [31,86].) BaMn 2 As 2 and LaMnAsO have five electrons in their 3dshells [133] and are therefore expected to be in the vicinity of a Mott-insulator phase. These systems have very high Neél temperatures of T N = 625 and 350 K, respectively.…”