Importance of electronic correlations in exploring the exotic phase diagram of layered <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Li</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>MnO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Hrishit Banerjee, Clare P. Grey, Andrew J. Morris
Abstract
Using ab initio dynamical mean-field theory we explore the electronic and magnetic states of layered ${\mathrm{Li}}_{x}{\mathrm{MnO}}_{2}$ as a function of $x$, the state-of-charge. Constructing real-space Wannier projections of Kohn-Sham orbitals based on the low-energy subspace of Mn $3d$ states and solving a multi-impurity problem, our approach focuses on local correlations at Mn sites. The antiferromagnetic insulating state in ${\mathrm{LiMnO}}_{2}$ has a moderate N\'eel temperature of ${T}_{N}=296\phantom{\rule{0.16em}{0ex}}\text{K}$ in agreement with experimental studies. Upon delithiation the system proceeds through a number of states: ferrimagnetic correlated metals at $x=0.92$, 0.83; multiple charge disproportionated ferromagnetic correlated metals with large quasiparticle peaks at $x=0.67$, 0.50, 0.33; ferromagnetic metals with small quasiparticle peaks at $x=0.17$, 0.08 and an antiferromagnetic insulator for the fully delithiated state, $x=0.0$. At moderate states of charge, $x=0.67\ensuremath{-}0.33$, a mix of $+3/+4$ formal oxidation states of Mn is observed, while the overall nominal oxidation of Mn state changes from $+3$ in ${\mathrm{LiMnO}}_{2}$ to $+4$ in ${\mathrm{MnO}}_{2}$. In all these cases the high-spin state emerges as the most likely state in our calculations considering the full $d$ manifold of Mn based on the proximity of ${e}_{g}$ levels in energy to ${t}_{2g}$. We observe a crossover from coherent to incoherent behavior on delithiation as function of state-of-charge.