PILLAR: Electron dynamics in laterally confined quasi-two-dimensional metals

PILLAR：横向约束准二维金属中的电子动力学

• 批准号: 501654252
• 负责人: Professor Dr. Philip Moll
• 金额: --
• 依托单位: Abteilung für Mikrostrukturierte Quantenmaterie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/501654252?language=en
• 关键词: PILLAR; Electron; dynamics; laterally; confined

Strongly layered materials have offered a wealth of exciting physical phenomena andnovel applications. These quasi-2D crystals (q2D) are defined by strong in-plane bondsand weak out-of-plane bonding. Exfoliation leads to often atomically thin flakes withelectronic, magnetic, optical and chemical properties that are strikingly different fromthe bulk. The key to their novel behavior is the reduction of the effective dimensionalityto the two in-plane dimensions. The most prominent examples of the concept ofexfoliating are undoubtedly graphite/graphene and the transition-metaldichalcogenides (TMD).If a crystal in three dimensions can be mechanically shaped to behave akin to a 2Dsystem, it must also be possible to generate quasi-1D states from it (3D = q2D + q1D).We call this limit "pillar", an infinite stack of mesoscopic (<1 micron) q2D flakes. Justlike their more familiar q2D cousins, dimensional reduction is expected to lead toelectronic behavior that is strikingly different to the bulk. Each plane of the pillar canbe viewed as an individual island that is weakly coupled to its upper and lowerneighbors, hence forming a new kind of q1D island chain. Here we propose to realizedand explore this state, by breaking the strong bonds while preserving the weak ones.While q2D sheets are easily prepared by exfoliation, pillars oppose the natural bondanisotropy and hence are difficult to obtain by conventional methods. We propose touse Focused Ion Beam machining as a gentle kinetic technique to carve such pillarsfrom bulk crystals.We plan to explore three main scientific topics based on the unique properties of q1Dpillars:1) A new regime of quantum transport in mesoscopic pillars in whichin-plane standing waves are coherently transported between the stacked sheets. Itshallmark is a novel magnetoconductance oscillation akin to the Aharonov-Bohm-effect,which we recently demonstrated in FIB-carved pillars of PdCoO2. Is this a unique caseof this delafossite metal, or a general property? Does it survive strong correlations and interact with superconductivity, e.g.in Sr2RuO4?2) Bloch-oscillations have never been observed (yet) in bulk crystalline metals. Wepropose that Landau-quantization in pillars induces shallow (flat) Landau-bands,which are ideally suited to realize Bloch oscillations. This will both be tackled viadc-transport and by building optical micro-resonators. If successful, it woulddemonstrate a field-tunable, solid-state frequency source in the THz range.3) Extreme conductivity anisotropy in layered metals provides a new approach to thetechnologically relevant field of transparent conductors. We plan to fabricate uniquepillar and slab structures of Sr2RuO4 with their atomic-interlayer direction in theplane of the substrate. Such material should be an excellent in-plane conductor whiletransmitting visible light when polarized perpendicular to the planes.

强层状材料提供了大量令人兴奋的物理现象和新颖的应用。这些准二维晶体（q2 D）由强的面内键和弱的面外键定义。剥落导致通常原子级的薄片，其电子、磁性、光学和化学性质与大块材料截然不同。其新颖行为的关键是将有效维数减少到两个面内维数。剥离概念最突出的例子无疑是石墨/石墨烯和过渡金属二硫属化物（TMD）。如果三维晶体可以机械成形为类似于2D系统的行为，那么它也必须有可能从它产生准1D状态（3D = q2 D + q1 D）。我们称这种极限为“柱”，即介观（<1微米）q2 D薄片的无限堆叠。就像他们更熟悉的q2 D表兄弟一样，降维预计会导致与体材料截然不同的电子行为。柱体的每个平面都可以看作是一个独立的岛，它与上下相邻的平面弱耦合，从而形成了一种新的q1 D岛链。在这里，我们建议realizedand探索这种状态，通过打破强键，同时保留弱的。虽然q2 D片很容易通过剥离制备，柱反对自然键各向异性，因此很难通过常规方法获得。我们计划利用聚焦离子束加工技术从块状晶体中切割出这样的柱状晶体，并基于q1 D柱状晶体的独特性质，探索三个主要的科学课题：1）介观柱状晶体中量子输运的新机制，其中面内驻波在堆叠层之间相干输运.它的标志是一种新的磁导振荡类似于Aharonov-Bohm效应，我们最近在FIB雕刻的PdCoO 2柱中证明了这一点。这是铜铁矿金属的一个特例还是一般性质？它是否存在强相关性并与超导性相互作用，e.g.in 2 RuO 4？2)布洛赫振荡从未在大块晶体金属中观察到过。我们提出，朗道量子化的支柱诱导浅（平）朗道带，这是理想的适合实现布洛赫振荡。这将通过高架桥运输和建立光学微谐振器来解决。如果成功，它将展示太赫兹范围内的场可调谐固态频率源。3）层状金属中的极端电导率各向异性为透明导体技术相关领域提供了一种新方法。我们计划制备Sr_2RuO_4的外延和板状结构，其原子-层间方向在衬底平面内。这种材料应该是一个优秀的面内导体，同时在垂直于平面偏振时透射可见光。