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<p>Nb<sub>3</sub>Cl<sub>8</sub> is a prototypical material that exhibits both a cluster Mott transition and flat band physics. In this work, we employ a parameter-free and self-consistent computational framework combining density-functional theory (DFT), the constrained random-phase approximation (cRPA), and dynamical mean-field theory (DMFT) to investigate the stability of the cluster Mott state under pressure. We reveal a pressure-induced local symmetry breaking of the Nb<sub>3</sub> trimers, from <i>C</i><sub>3<i>v</i></sub> to <i>C</i><sub><i>s</i></sub>, which enhances the bandwidth and lifts degeneracies. Despite this symmetry reduction, the cluster Mott insulating state remains robust at high pressure (HP). The experimentally observed reduction of the charge gap arises from both the pressure-induced bandwidth increase and the suppression of Coulomb interactions due to enhanced screening. Our study provides a systematic theoretical account of how pressure-driven structural changes shape the electronic structure and correlation strength in a cluster Mott insulator, offering a solid foundation for understanding the interplay among symmetry, local and nonlocal correlations, and emergent quantum phases in correlated cluster materials.</p>

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Pressure-robust cluster Mott states in the layered compound Nb3Cl8

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月5日

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  • Hongbin Qu,
  • Xiaoqun Wang,
  • Hai-Qing Lin,
  • Gang Li

摘要

Nb3Cl8 is a prototypical material that exhibits both a cluster Mott transition and flat band physics. In this work, we employ a parameter-free and self-consistent computational framework combining density-functional theory (DFT), the constrained random-phase approximation (cRPA), and dynamical mean-field theory (DMFT) to investigate the stability of the cluster Mott state under pressure. We reveal a pressure-induced local symmetry breaking of the Nb3 trimers, from C3v to Cs, which enhances the bandwidth and lifts degeneracies. Despite this symmetry reduction, the cluster Mott insulating state remains robust at high pressure (HP). The experimentally observed reduction of the charge gap arises from both the pressure-induced bandwidth increase and the suppression of Coulomb interactions due to enhanced screening. Our study provides a systematic theoretical account of how pressure-driven structural changes shape the electronic structure and correlation strength in a cluster Mott insulator, offering a solid foundation for understanding the interplay among symmetry, local and nonlocal correlations, and emergent quantum phases in correlated cluster materials.