Ferromagnetic insulators and plasmons have attracted a lot of interest due to their rich fundamental science and applications. Recent research efforts have been made to find dopant-free ferromagnetic insulators and unconventional plasmons independently both in strongly correlated electron systems. However, our understanding of them is still lacking. Existing dopant-free ferromagnetic insulator materials are mostly limited to complex d- or f-systems with extremely low Curie temperature, low-symmetry structure, and strict growth conditions on specific substrates, limiting their compatibility with industrial applications. Unconventional plasmon is, on the other hand, a quasiparticle that originates from the collective excitation of correlated-charges, yet they are rarely explored, particularly in ferromagnetic insulator materials. Herewith, we present a novel, room temperature dopant-free ferromagnetic Mott-like insulator with a high-symmetry structure in unconventional strongly correlated s band of low-dimensional highly oriented single-crystal gold quantum dots (HOSG-QDs) on MgO(001). Interestingly, HOSG-QDs show new high-energy correlated-plasmons with low-plasmonics-loss. With a series of state-of-the-art experimental techniques, we find that the Mott-insulating state is tunable with surprisingly strong spin-splitting and spin polarization accompanied by strong s–s transitions, disappearance of Drude response, and generating new Mott-like gap. Supported with a series of theoretical calculations, the interplay of quantum confinement, many-body electronic correlations, and hybridizations tunes electron–electron correlations in s band and determines the ferromagnetism, Mott-like insulator, and high-energy correlated-plasmons. Our result shows a new class of room temperature dopant-free ferromagnetic Mott-like insulator and high-energy correlated-plasmons with low-loss in strongly correlated s band and opens unexplored applications of low-dimensional gold in spin field-effect transistors and plasmonics.

中文翻译：

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新型无掺杂铁磁 Mott 状绝缘体和高能相关等离子体在非常规低维金强相关 s 波段中的应用


铁磁绝缘体和等离激元因其丰富的基础科学和应用而引起了人们的广泛兴趣。最近的研究工作已经进行了研究，以独立地在强相关电子系统中找到无掺杂剂的铁磁绝缘体和非常规等离激元。然而，我们对它们的理解仍然缺乏。现有的无掺杂铁磁绝缘体材料大多局限于复杂的 d 或 f 系统，具有极低的居里温度、低对称性结构和特定衬底上的严格生长条件，限制了它们与工业应用的兼容性。另一方面，非常规等离激元是一种起源于相关电荷集体激发的准粒子，但它们很少被探索，尤其是在铁磁绝缘体材料中。在此，我们提出了一种新型的、室温下无掺杂剂的铁磁 Mott 状绝缘体，在 MgO（001） 上的低维高度取向单晶金量子点 （HOSG-QD） 的非常规强相关 s 波段中具有高对称结构。有趣的是，HOSG-QDs 显示出新的高能相关等离激元和低等离激元损耗。通过一系列最先进的实验技术，我们发现 Mott 绝缘态是可调的，具有令人惊讶的强自旋分裂和自旋极化，并伴有强烈的 s-s 跃迁，Drude 响应消失，并产生新的类似 Mott 的间隙。在一系列理论计算的支持下，量子限制、多体电子相关性和杂化的相互作用调整了 s 波段的电子-电子相关性，并确定了铁磁性、Mott 状绝缘体和高能相关等离激元。 我们的结果显示了一类新的室温无掺杂铁磁 Mott 状绝缘体和高能量相关等离子体，在强相关 s 波段具有低损耗，并开辟了低维金在自旋场效应晶体管和等离子体学中尚未探索的应用。