Hund flat band in a frustrated spinel oxide
Abstract
Electronic flat bands associated with quenched kinetic energy and heavy electron mass have attracted great interest for promoting strong electronic correlations and emergent phenomena such as high-temperature charge fractionalization and superconductivity. Intense experimental and theoretical research has been devoted to establishing the rich non-trivial metallic and heavy fermion phases intertwined with such localized electronic states. Here, we investigate the transition metal oxide spinel LiV2O4, an enigmatic heavy fermion compound lacking localized f orbital states. We use angle-resolved photoemission spectroscopy and dynamical mean field theory to reveal a new kind of correlation-induced flat band with suppressed inter-atomic electron hopping arising from intra-atomic Hund coupling. The appearance of heavy quasiparticles is ascribed to a proximate orbital-selective Mott state characterized by fluctuating local moments as evidenced by complementary magnetotransport measurements. The spectroscopic fingerprints of long-lived quasiparticles and their disappearance with increasing temperature further support the emergence of a high-temperature bad metal state observed in transport data. This work resolves a long-standing puzzle on the origin of heavy fermion behavior and unconventional transport in LiV2O4. Simultaneously, it opens a new path to achieving flat bands through electronic interactions in d-orbital systems with geometrical frustration, potentially enabling the realization of exotic phases of matter such as the fractionalized Fermi liquids.
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BibTeX
@article{oh2026hund,
title = {{Hund flat band in a frustrated spinel oxide}},
author = {Dongjin Oh and Alexander Hampel and Joshua P Wakefield and Peter Moen and Steef Smit and Xiangyu Luo and Marta Zonno and Sergey Gorovikov and Mats Leandersson and Craig Polley and Asish K Kundu and Anil Rajapitamahuni and Elio Vescovo and Chris Jozwiak and Aaron Bostwick and Eli Rotenberg and Masahiko Isobe and Manish Verma and Matteo Crispino and Martin Grundner and Fabian B Kugler and Olivier Parcollet and Ulrich Schollwöck and Hidenori Takagi and Andrea Damascelli and Giorgio Sangiovanni and Joseph G Checkelsky and Antoine Georges and Riccardo Comin},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2026},
month = oct,
doi = {10.1073/pnas.2518213122},
eprint = {2502.07234},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05507548v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Hund flat band in a frustrated spinel oxide
AU - Dongjin Oh
AU - Alexander Hampel
AU - Joshua P Wakefield
AU - Peter Moen
AU - Steef Smit
AU - Xiangyu Luo
AU - Marta Zonno
AU - Sergey Gorovikov
AU - Mats Leandersson
AU - Craig Polley
AU - Asish K Kundu
AU - Anil Rajapitamahuni
AU - Elio Vescovo
AU - Chris Jozwiak
AU - Aaron Bostwick
AU - Eli Rotenberg
AU - Masahiko Isobe
AU - Manish Verma
AU - Matteo Crispino
AU - Martin Grundner
AU - Fabian B Kugler
AU - Olivier Parcollet
AU - Ulrich Schollwöck
AU - Hidenori Takagi
AU - Andrea Damascelli
AU - Giorgio Sangiovanni
AU - Joseph G Checkelsky
AU - Antoine Georges
AU - Riccardo Comin
PY - 2026
DA - 2026/10/14
JO - Proceedings of the National Academy of Sciences of the United States of America
DO - 10.1073/pnas.2518213122
UR - https://hal.science/hal-05507548v1
AB - Electronic flat bands associated with quenched kinetic energy and heavy electron mass have attracted great interest for promoting strong electronic correlations and emergent phenomena such as high-temperature charge fractionalization and superconductivity. Intense experimental and theoretical research has been devoted to establishing the rich non-trivial metallic and heavy fermion phases intertwined with such localized electronic states. Here, we investigate the transition metal oxide spinel LiV2O4, an enigmatic heavy fermion compound lacking localized f orbital states. We use angle-resolved photoemission spectroscopy and dynamical mean field theory to reveal a new kind of correlation-induced flat band with suppressed inter-atomic electron hopping arising from intra-atomic Hund coupling. The appearance of heavy quasiparticles is ascribed to a proximate orbital-selective Mott state characterized by fluctuating local moments as evidenced by complementary magnetotransport measurements. The spectroscopic fingerprints of long-lived quasiparticles and their disappearance with increasing temperature further support the emergence of a high-temperature bad metal state observed in transport data. This work resolves a long-standing puzzle on the origin of heavy fermion behavior and unconventional transport in LiV2O4. Simultaneously, it opens a new path to achieving flat bands through electronic interactions in d-orbital systems with geometrical frustration, potentially enabling the realization of exotic phases of matter such as the fractionalized Fermi liquids.
SN - 0027-8424
SN - 1091-6490
ER -