Quasiparticle interference of heavy fermions in resonant X-ray scattering

TL;DR

This study demonstrates that resonant X-ray scattering can detect quasiparticle interference signals in heavy fermion materials, providing a new method to probe bulk electronic structures with element and orbital specificity.

Contribution

We experimentally show that quasiparticle interference signals in heavy fermion compounds can be observed via resonant X-ray scattering, linking RXS data with STM measurements.

Findings

RXS measurements reveal a broad scattering enhancement correlated with heavy f-electron bands.

The RXS scattering enhancement matches STM quasiparticle interference signals.

Quasiparticle interference can be probed through RXS momentum distribution.

Abstract

Resonant X-ray scattering (RXS) has recently become an increasingly important tool for the study of ordering phenomena in correlated electron systems. Yet, the interpretation of the RXS experiments remains theoretically challenging due to the complexity of the RXS cross-section. Central to this debate is the recent proposal that impurity-induced Friedel oscillations, akin to quasiparticle interference signals observed with the scanning tunneling microscope (STM), can lead to scattering peaks in the RXS experiments. The possibility that quasiparticle properties can be probed in RXS measurements opens up a new avenue to study the bulk band structure of materials with the orbital and element selectivity provided by RXS. Here, we test these ideas by combining RXS and STM measurements of the heavy fermion compound CeMIn$_5$ (M = Co, Rh). Temperature and doping dependent RXS measurements at the Ce-M$_4$ edge show a broad scattering enhancement that correlates with the appearance of heavy f-electron bands in these compounds. The scattering enhancement is consistent with the measured quasiparticle interference signal in the STM measurements, indicating that quasiparticle interference can be probed through the momentum distribution of RXS signals. Overall, our experiments demonstrate new opportunities for studies of correlated electronic systems using the RXS technique.