Plasmon Collapse in a Directional Strange Metal
Abstract
Strange metals are widespread in strongly correlated quantum matter and closely intertwined with high-temperature superconductivity and quantum criticality, yet their microscopic charge dynamics remain fundamentally unresolved. Whether well-defined collective modes survive in an incoherent electronic fluid or dissolve into overdamped continua remains intensely debated. Here, employing high-momentum-resolution inelastic electron scattering complemented by direction-resolved transport, we show that the van der Waals compound MoOCl2, a "bad" metal known to host unusually "good" plasmons, exhibits a striking dichotomy in electronic coherence and charge dynamics. Transport reveals coherent Fermi liquid behavior along one in-plane crystallographic axis and an incoherent strange metal response along the orthogonal axis. This dichotomy extends directly to the charge response. The Fermi liquid direction supports a well-defined, long-lived plasmon, whereas the strange metal direction exhibits an overdamped excitation that progressively loses its collective character with increasing momentum. Beyond a critical momentum (qc ≈ 0.008 mathringA−1), the mode undergoes a reversal into negative dispersion and ultimately collapses into a broad, nearly featureless continuum with a robust high-energy boundary (Ec ≈ 1.75 eV). Remarkably, thickness-dependent measurements show that both qc and Ec remain nearly unchanged despite substantial modifications of Coulomb screening, revealing them as intrinsic scales of incoherent charge density fluctuations. These results establish a unique single-material platform in which coherent and incoherent electronic states are partitioned into in-plane orthogonal channels, and demonstrate that incoherent electronic fluids retain intrinsically structured charge dynamics beyond the quasiparticle paradigm.
Related
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- Entanglement entropy of fermions in a strange metal
- Planckian dissipation per unit critical entropy as a coupling-free probe of the strange-metal bath
- Strange-metal behavior in correlated molecular conductors
- Extended strange metal and superconductivity in partially filled moiré Hubbard bands
BibTeX
@misc{li2026plasmon,
title = {{Plasmon Collapse in a Directional Strange Metal}},
author = {Jiade Li and Peiyi He and Deng Hu and Jiakai Wang and Jifeng Shao and Wan-Shun Du and Xuetao Zhu and Jiandong Guo and Zhiwei Wang and Peng Gao},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21209},
eprint = {2610.21209},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21209},
}
RIS
TY - UNPB
TI - Plasmon Collapse in a Directional Strange Metal
AU - Jiade Li
AU - Peiyi He
AU - Deng Hu
AU - Jiakai Wang
AU - Jifeng Shao
AU - Wan-Shun Du
AU - Xuetao Zhu
AU - Jiandong Guo
AU - Zhiwei Wang
AU - Peng Gao
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21209
UR - https://arxiv.org/abs/2610.21209
AB - Strange metals are widespread in strongly correlated quantum matter and closely intertwined with high-temperature superconductivity and quantum criticality, yet their microscopic charge dynamics remain fundamentally unresolved. Whether well-defined collective modes survive in an incoherent electronic fluid or dissolve into overdamped continua remains intensely debated. Here, employing high-momentum-resolution inelastic electron scattering complemented by direction-resolved transport, we show that the van der Waals compound MoOCl_2, a "bad" metal known to host unusually "good" plasmons, exhibits a striking dichotomy in electronic coherence and charge dynamics. Transport reveals coherent Fermi liquid behavior along one in-plane crystallographic axis and an incoherent strange metal response along the orthogonal axis. This dichotomy extends directly to the charge response. The Fermi liquid direction supports a well-defined, long-lived plasmon, whereas the strange metal direction exhibits an overdamped excitation that progressively loses its collective character with increasing momentum. Beyond a critical momentum (q_c ≈ 0.008 mathringA^−1), the mode undergoes a reversal into negative dispersion and ultimately collapses into a broad, nearly featureless continuum with a robust high-energy boundary (E_c ≈ 1.75 eV). Remarkably, thickness-dependent measurements show that both q_c and E_c remain nearly unchanged despite substantial modifications of Coulomb screening, revealing them as intrinsic scales of incoherent charge density fluctuations. These results establish a unique single-material platform in which coherent and incoherent electronic states are partitioned into in-plane orthogonal channels, and demonstrate that incoherent electronic fluids retain intrinsically structured charge dynamics beyond the quasiparticle paradigm.
ER -