Prof Yulin Chen

Abstract:

PrAlSi, a non‐centrosymmetric ferromagnetic Weyl semimetal candidate with a Curie temperature of 17.8K, offers a unique platform for exploring the interplay of symmetry breaking and topological electronic structures. Up to now, the Weyl fermion distribution as well as their evolution across the ferromagnetic to paramagnetic phase transition in PrAlSi has not been explored. Here, the presence of Weyl fermions is uncovered in PrAlSi and demonstrates that they can be manipulated through the magnetic phase transition. The ab‐initio calculations indicate a shift in the momentum and energy positions of Weyl fermions, alongside an increase in Weyl point numbers due to band splitting. The predicted band splitting and shifting of Weyl fermions are corroborated by the angle‐resolved photoemission spectroscopy experiments. Such manipulation of Weyl fermions leads to the appearance of a net chirality charge and a significant modulation in optical conductivity, as proposed by the calculations. The research presents a novel method for adjusting the properties of Weyl semimetals by controlling Weyl fermions through magnetic phase transitions, positioning PrAlSi as a model system.

Abstract:

Correlated kagome materials exhibit a compelling interplay between lattice geometry, electron correlation, and topology. In particular, the flat bands near the Fermi level provide a fertile playground for novel many-body states. Here we investigate the electronic structure of CsCr3Sb5 using high-resolution angle-resolved photoemission spectroscopy and ab-initio calculations. Our results suggest that Cr 3d electrons are intrinsically incoherent, showing strong electron correlation amplified by Hund’s coupling. Notably, we identify incipient flat bands close to the Fermi level, which are expected to significantly influence the electronic properties of the system. Across the density-wave-like transition at 55 K, we observe a drastic enhancement of the electron scattering rate, which aligns with the semiconducting-like property at high temperatures. These findings establish CsCr3Sb5 as a strongly correlated Hund’s metal with incipient flat bands near the Fermi level, which provides an electronic basis for understanding its novel properties compared to the weakly correlated AV3Sb5.