Electronic structure study of LaCoIn5 and its comparison with CeCoIn5

Abstract

A central key to understanding heavy-fermion systems involves revealing how itinerant low-energy excitations emerge from local $f$ moments. An effective way to understand the $f$-electron behavior is to compare the electronic structure of $f$-electron compounds with a reference isostructural compound with no $f$ electrons. Here we present a systematic electronic structure study of ${\mathrm{LaCoIn}}_{5}$, which is a non-$f$ reference compound of the heavy-fermion superconductor ${\mathrm{CeCoIn}}_{5}$. Our angle-resolved photoemission spectroscopy study of the three-dimensional Fermi surface and band structure of ${\mathrm{LaCoIn}}_{5}$ highlights the rather three-dimensional electronic character of this compound. The conduction bands of ${\mathrm{LaCoIn}}_{5}$ are almost identical to that of ${\mathrm{CeCoIn}}_{5}$, though obvious differences can be found in the low-energy electronic structure. Finally, we give a quantitative analysis of the Fermi pocket change in ${\mathrm{LaCoIn}}_{5}$ and ${\mathrm{CeCoIn}}_{5}$, which may be helpful for understanding the important ``large'' and ``small'' Fermi surface issue in heavy-fermion compounds.