Electronic structures of modulated charge density waves in a kagome metal FeGe*

The discovery of a charge density wave (CDW) phase in the A-type antiferromagnetic order of the kagome metal FeGe solidifies the unique standing of FeGe among kagome systems. Our earlier studies revealed characteristic electronic structures from the kagome lattice, namely flat bands, Dirac crossings, and Van Hove singularities using angle-resolved photoemission spectroscopy (ARPES). We have also identified the temperature dependence of a Van Hove singularity and moderate electron-phonon interactions, providing insights into the correlated characteristics of FeGe.

Recently, studies have reported that the CDW in FeGe can be modulated by post-annealing processes, realizing the tuning of the CDW order between long-range order and complete suppression. This newly discovered tunability has opened up opportunities for further in-depth investigations of the CDW in FeGe. We have successfully reproduced long-range CDW order and its suppression by changing post-annealing conditions. Physical property characterizations including magnetic susceptibility agree with existing reports. In this presentation, we will present electronic structure characterizations of both the long-range and suppressed CDW phases in FeGe by ARPES. Temperature-dependent electronic structures will be discussed as well, highlighting the discovery of multiple temperature scales that either differ or coincide in both phases. Our systematic comparison between the two phases helps understanding the nature of CDW phases in terms of electronic structures, opening ways to examine novel mechanism that intertwines CDW and other orders in kagome lattices.