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rlafite木蟲(chóng) (正式寫(xiě)手)
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莫特絕緣體與近藤絕緣體——外部刺激如何改變電子能帶
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莫特絕緣體與近藤絕緣體——外部刺激如何改變電子能帶 來(lái)自材料納米結(jié)構(gòu)學(xué)研究中心(MANA)的最新研究揭示了一種理論機(jī)制,闡明強(qiáng)關(guān)聯(lián)絕緣體的電子能帶結(jié)構(gòu)如何在自旋與電荷擾動(dòng)作用下被重塑,為實(shí)現(xiàn)可調(diào)控能帶結(jié)構(gòu)的電子器件開(kāi)辟了新可能。 設(shè)想一種電子材料,其基本性質(zhì)的改變并不依賴于替換原子或制備新的結(jié)構(gòu),而是通過(guò)施加光照、磁場(chǎng)或電信號(hào)來(lái)實(shí)現(xiàn)。例如,一種太陽(yáng)能電池可以在光照條件下暫時(shí)重塑其能帶結(jié)構(gòu),從而更高效地吸收光能。 在傳統(tǒng)半導(dǎo)體中,這種靈活性通常難以實(shí)現(xiàn),因?yàn)橥獠空{(diào)控只能改變電子對(duì)能級(jí)的占據(jù)情況,而無(wú)法真正改變能帶結(jié)構(gòu)本身。 如今,發(fā)表在Physical Review B上的一項(xiàng)研究表明,強(qiáng)關(guān)聯(lián)絕緣體(如莫特絕緣體和近藤絕緣體)可以表現(xiàn)出截然不同的行為。該研究由 MANA 的首席研究員 Masanori Kohno 完成。 在這些材料中,通過(guò)摻雜(通過(guò)化學(xué)勢(shì)移動(dòng)引入空穴或電子)、磁化或光照等方式擾動(dòng)自旋或電荷,可以在能帶之間的能隙內(nèi)誘導(dǎo)出全新的電子態(tài)。這種現(xiàn)象源于電子之間的強(qiáng)相互作用。 與普通帶隙絕緣體不同,在后者中自旋與電荷激發(fā)緊密耦合,而在強(qiáng)關(guān)聯(lián)絕緣體中,低能自旋激發(fā)可以獨(dú)立存在。 通過(guò)理論分析和數(shù)值計(jì)算,該研究闡明了自旋和電荷擾動(dòng)如何影響這些絕緣體的能帶結(jié)構(gòu),揭示了這些新電子模式產(chǎn)生的微觀機(jī)制。結(jié)果表明,當(dāng)大量自旋或電荷發(fā)生集體激發(fā)時(shí),所誘導(dǎo)的態(tài)可以具有顯著的譜強(qiáng)度,從而重塑電子能帶結(jié)構(gòu)。 “這項(xiàng)研究表明,與傳統(tǒng)半導(dǎo)體不同,自旋和電荷擾動(dòng)能夠產(chǎn)生新的電子模式,并主動(dòng)改變能帶結(jié)構(gòu),”Kohno 博士表示。 這些發(fā)現(xiàn)為基于強(qiáng)電子關(guān)聯(lián)效應(yīng)的能帶結(jié)構(gòu)工程奠定了基礎(chǔ),有望推動(dòng)未來(lái)具有增強(qiáng)功能和可調(diào)控性能的電子與光電子器件的發(fā)展。 Publication details Masanori Kohno, Electronic modes induced by spin and charge perturbations in Mott and Kondo insulators, Physical Review B (2025). DOI: 10.1103/ythd-s2x8 Abstract Electronic band structures usually remain unaffected by doping via a chemical-potential shift or by increasing the temperature in conventional band insulators. In contrast, it has been shown that those of Mott and Kondo insulators can be altered by doping or by increasing the temperature: electronic modes are induced within the band gap, exhibiting momentum-shifted magnetic dispersion relations from the band edges. Here, this study demonstrates that the underlying mechanism of the remarkable strong-correlation effects can be generalized to the emergence of electronic modes caused by various spin and charge perturbations, including magnetization of spin-gapped Mott and Kondo insulators. These emergent modes can alter the band structure if a macroscopic number of spins or charges are excited by the perturbations at a given moment. The origins and dispersion relations of these emergent modes, particularly why and how the dispersion relations depend on the momentum and energy of the perturbations, are elucidated by investigating the selection rules and using the Bethe ansatz and the effective theory for weak inter-unit-cell hopping. The validity and generality of the theoretical results across different models and spatial dimensions are verified by numerical calculations for the one- and two-dimensional Hubbard models, periodic Anderson models, Kondo lattice models, and ladder and bilayer Hubbard models. This study provides crucial insights into why and how spin and charge perturbations can alter the band structure in strongly correlated insulators, thereby paving the way for band-structure engineering in strong-correlation electronics, which enables previously unexplored functionalities by exploiting the unconventional characteristics revealed in this paper. |
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