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arXiv · 2603.22695

Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator

Zhibin Su·Junjian Mi·Shaohua Yan·Jiade Li·Siwei Xue·Zhiyu Tao·Enling Wang·Xiongfei Shi·Hechang Lei·Zhuan Xu·Jiandong Guo·Xuetao Zhu
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Abstract

Excitonic band structure is critical for investigating exciton dynamics. Theoretically, quantum effects from exchange scattering between electron-hole pairs significantly modulate exciton dispersion. Here, we report the direct observation of dimensionality-dependent exciton dispersion in a single-band Mott insulator Nb3Cl8 through high-resolution electron energy loss spectroscopy. In the high-temperature phase, the exciton in Nb3Cl8 hosts an exceptionally large binding energy, and exhibits clear quasi-two-dimensional massless linear dispersion. In contrast, in the low-temperature phase, the exciton splits into two bands, both displaying three-dimensional parabolic dispersion. These dramatic changes in the exciton dispersion stem from the dimensional mutation driven by a substantial enhancement of interlayer coupling across the phase transition. This Letter provides a clear and typical example of how exciton behavior evolves with dimensionality.

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Zhibin Su, Junjian Mi, Shaohua Yan, Jiade Li, Siwei Xue, Zhiyu Tao, Enling Wang, Xiongfei Shi, Hechang Lei, Zhuan Xu, Jiandong Guo, Xuetao Zhu. 2026-03-24. Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator. https://doi.org/10.1103/1z8v-hvkf

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