Correlation-driven 3d orbital heavy fermion behavior uncovered in the 3-dimensional electronic structure of LiV₂O₄

Heavy fermion materials have long attracted interest in condensed matter physics for hosting correlation-driven exotic quantum states. Remarkably, the oxide spinel LiV₂O₄ exhibits heavy fermion characteristics with a large Sommerfeld coefficient and effective mass reaching ~180 times the free electron mass—despite the complete absence of f-electrons. For over thirty years since its discovery, the microscopic origin of the 3d orbital heavy fermion behavior has remained elusive.

By combining high-quality thin film growth and angle-resolved photoemission spectroscopy (ARPES) measuremets, a research team led by Professors Rui Peng and Haichao Xu from Fudan University has made a breakthrough in revealing the three-dimensional electronic structure of LiV₂O₄ and the mechanism of its 3d orbital heavy fermion behavior.

Researchers have detected a flat band near the Fermi level, derived from the V a₁_g orbital, with a significantly reduced bandwidth of only 25 meV. These findings are consistent with dynamical mean-field theory (DMFT) calculations and underscore how strong electron correlations and Hund’s coupling drive this orbital toward a Mott state. The band displays electron-like dispersion and gives an effective mass of approximately 19mₑ based on parabolic fitting. Moreover, further renormalization within a few meV of the Fermi level enhances the effective mass by another five times. "The flat band we resolved isn’t just narrowed by Hund-assisted electron-electron correlation—it’s further renormalized at the lowest energies, pointing to the possible role of geometric frustration and low-energy spin fluctuations in making the electrons even heavier." said Prof. Xu Haichao.

This work not only solves a long-standing mystery in LiV₂O₄ but also suggests a novel pathway toward realizing heavy fermion states in transition metal oxides through a combination of strong correlations, Hund’s coupling, and frustrated lattice geometry. The team plans to extend these measurements to even lower temperatures and higher energy resolution to fully resolve the quasiparticle dispersion in the coherent heavy Fermi liquid state.

The findings were published in Chinese Physics Letters (DOI: 10.1088/0256-307X/42/10/100710).

See the article:

Correlation-Driven 3d Heavy Fermion Behavior in LiV₂O₄

(https://iopscience.iop.org/article/10.1088/0256-307X/42/10/100710)