Villalpando Graciela, Jovanovic Milena, Hoff Brianna, Jiang Yi, Singha Ratnadwip, Yuan Fang, Hu Haoyu, Călugăru Dumitru, Mathur Nitish, Khoury Jason F, Dulovic Stephanie, Singh Birender, Plisson Vincent M, Pollak Connor J, Moya Jaime M, Burch Kenneth S, Bernevig B Andrei, Schoop Leslie M
Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
Department of Chemistry, North Carolina State University, Raleigh, NC 27606, USA.
Sci Adv. 2024 Sep 20;10(38):eadl1103. doi: 10.1126/sciadv.adl1103.
Flat bands that do not merely arise from weak interactions can produce exotic physical properties, such as superconductivity or correlated many-body effects. The quantum metric can differentiate whether flat bands will result in correlated physics or are merely dangling bonds. A potential avenue for achieving correlated flat bands involves leveraging geometrical constraints within specific lattice structures, such as the kagome lattice; however, materials are often more complex. In these cases, quantum geometry becomes a powerful indicator of the nature of bands with small dispersions. We present a simple, soft-chemical processing route to access a flat band with an extended quantum metric below the Fermi level. By oxidizing Ni-kagome material CsNiS to CsNiS, we see a two orders of magnitude drop in the room temperature resistance. However, CsNiS is still insulating, with no evidence of a phase transition. Using experimental data, density functional theory calculations, and symmetry analysis, our results suggest the emergence of a correlated insulating state of unknown origin.
并非仅仅由弱相互作用产生的平带能够产生奇异的物理性质，例如超导性或相关的多体效应。量子度量可以区分平带是会导致相关物理现象还是仅仅是悬挂键。实现相关平带的一个潜在途径涉及利用特定晶格结构（如 Kagome 晶格）内的几何约束；然而，材料往往更为复杂。在这些情况下，量子几何成为具有小色散的能带性质的有力指标。我们提出了一种简单的软化学处理路线，以获得费米能级以下具有扩展量子度量的平带。通过将镍基 Kagome 材料 CsNiS 氧化为 CsNiS，我们观察到室温电阻下降了两个数量级。然而，CsNiS 仍然是绝缘的，没有相变的迹象。利用实验数据、密度泛函理论计算和对称性分析，我们的结果表明出现了一种来源不明的相关绝缘态。
