Non-Fermi Liquid Behaviour in a Correlated Flat-band Pyrochlore Lattice

Result of the Month

Figure shows a quantum destructive interference-induced topological flat band renormalized to the Fermi level by electron correlation effect. Image credit to Jianwei Huang, first author of the publication.

Author: Jianwei Huang, Lei Chen, Yuefei Huang, Chandan Setty, Bin Gao, Yue Shi, Zhaoyu Liu, Yichen Zhang, Turgut Yilmaz, Elio Vescovo, Makoto Hashimoto, Donghui Lu, Boris I. Yakobson, Pengcheng Dai, Jiun-Haw Chu, Qimiao Si, Ming Yi Institute: ''Department of Physics and Astronomy, Rice University, Houston, Texas, USA '' Date: 3/2024 Instruments: DA30-L

TElectronic correlation effects are manifested in quantum materials when either the on-site Coulomb repulsion is large or the electron kinetic energy is small. The former is the dominant effect in cuprate superconductors and heavy-fermion systems whereas it is the latter in twisted bilayer graphene and geometrically frustrated metals. However, the simultaneous cooperation of both effects in the same quantum material remains rare. The design aim is to produce correlated topological flat bands pinned at the Fermi level. Here, they observe a flat band at the Fermi level in a 3d pyrochlore metal CuV2S4. Their angle-resolved photoemission spectroscopy data reveal that destructive quantum interference associated with the V pyrochlore sublattice and further renormalization to the Fermi level by electron interactions induce this flat band. Consequently, they discover transport signatures that evidence a deviation from Fermi liquid behaviour as well as an enhanced Sommerfeld coefficient. Their work illustrates the combined cooperation of local Coulomb interactions and geometric frustration in a pyrochlore lattice system to induce correlated topology by constructing and pinning correlated flat bands near the Fermi level.

The emergence of topological flat bands through quantum destructive interference in geometrically-frustrated lattices is a prominent topic in condensed matter physics. However, experimental evidence of such phenomena in three dimensions remains elusive. Here, we employ angle-resolved photoemission spectroscopy to investigate a three-dimensional (3D) pyrochlore lattice metal, CuV2S4. Our observations reveal a 3D topological flat band induced by quantum destructive interference within the V pyrochlore sublattice. Furthermore, this flat band undergoes renormalization to the Fermi level due to electron correlation effect, consequently leading to non-Fermi liquid behavior in the pyrochlore metal.