Orbital anisotropy of heavy fermion <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>Ce</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi>IrIn</mml:mi></mml:mrow><mml:mn>8</mml:mn></mml:msub></mml:math> under crystalline electric field and its energy scale

Abstract

We investigate the temperature (T) evolution of orbital anisotropy and its effect on spectral function and optical conductivity in Ce2IrIn8 using a first-principles dynamical mean-field theory combined with density functional theory. The orbital anisotropy develops by lowering T and it is intensified below a temperature corresponding to the crystalline-electric field (CEF) splitting size. Interestingly, the depopulation of CEF excited states leaves a spectroscopic signature, "shoulder,"in the T-dependent spectral function at the Fermi level. From the two-orbital Anderson impurity model, we demonstrate that CEF splitting size is the key ingredient influencing the emergence and the position of the "shoulder."Besides the two conventional temperature scales TK and T∗, we introduce an additional temperature scale to deal with the orbital anisotropy in heavy fermion systems. © 2022 American Physical Society.