Anisotropy of Kondo-lattice coherence in momentum space for CeCoIn5

TL;DR

This study uses polarization-resolved Raman spectroscopy to investigate the anisotropic electronic coherence in CeCoIn5, revealing band-specific coherence development and phonon anomalies below the Kondo coherence temperature.

Contribution

It provides new insights into the momentum-space anisotropy of Kondo-lattice coherence and electron-phonon interactions in CeCoIn5, highlighting band-dependent coherence behavior.

Findings

Coherence develops in $eta$ and $eta$ bands below T*

Phonon modes show anomalies below T*

Electronic scattering rate reduces due to coherence

Abstract

We study the electronic and phononic excitations of heavy-fermion metal CeCoIn$_5$ by polarization-resolved Raman spectroscopy to explore the Kondo-lattice coherence. Below the coherence temperature T*\,=\,45\,K, the continuum of electronic excitations in the XY scattering geometry is suppressed at frequencies below 50\,cm$^{-1}$, whereas the low-frequency continuum in the X'Y' geometry exhibits no change across T*. We relate the suppression to the reduced electron-electron scattering rate resulting from the coherence effect. The presence of suppression in the XY geometry and absence of it in the X'Y' geometry implies that the $\alpha$ and $\beta$ bands become coherent below T*, whereas the $\gamma$ band remains largely incoherent down to 10\,K. Moreover, two optical phonon modes exhibit anomalies in their temperature dependence of the frequency and linewidth below T*, which results from developing coherent spectral weight near the Fermi level and reduced electron-phonon scattering rate. Our results further support the key role of anisotropic hybridization in CeCoIn$_5$.