Band flattening at the Fermi level as a precursor of quantum electron crystallization

费米能级的能带平坦化是量子电子结晶的前兆

• 批准号: 1904024
• 负责人: Sergey Kravchenko
• 金额: $ 31.75万
• 依托单位: Northeastern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-12-15 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904024&HistoricalAwards=false
• 关键词: Band; flattening; Fermi; level; precursor

Non-Technical AbstractConstruction of room-temperature superconductors has been a dream since the discovery of the superconductivity in 1911. For quite a while, the highest temperature, at which superconductivity was observed, remained at 23 K (or -250 C); however, in 1986, high-temperature superconductors were discovered with superconductivity surviving up to 138 K (or -135 C) and, more recently, even up to 203 K (-70 C) under high pressure. Presently, the most promising candidates for room-temperature superconductivity are the so-called 'flat-band materials' (i.e., the materials in which the energy of electrons does not depend on their momentum in some range of momenta). The PI and his team have recently discovered such behavior in silicon-germanium quantum wells and are pursuing the investigation of this material. The proposed activities offer unique opportunities to train students in novel technologies at the cutting edge of present-day capabilities. Northeastern University is famous for it's signature cooperative learning ('co-op') education, which affords students the opportunity for hands-on experiential learning during their studies. Within this program, the PI has a remarkable record in training undergraduate and graduate students in his laboratory.Technical AbstractThe proposed work is an experimental effort to unequivocally establish the flattening of the electronic band in the two-dimensional electron systems that may be vital for the construction of the room temperature superconductivity. The team intends to study silicon-germanium quantum wells of unprecedented quality developed by the PI?s group, as well as ZnO-based heterostructures of comparable quality. In the past, the band flattening in silicon-germanium quantum wells was observed by transport methods by the PI's team. However, the thermodynamic characteristics, like the spectrum of electrons, can only be reliably obtained by thermodynamic measurements. The PI and his team intend to use the techniques already available in the PI?s laboratory at Northeastern University to measure the thermodynamic magnetization and the thermopower of the electrons in two-dimensional systems. The first method yields the energy-averaged effective mass of the electrons; the second method yields the effective mass on the Fermi level. The saturation of the energy-averages mass and the divergence of the mass at the Fermi level in the limit of very low electron densities is the hallmark of the flattening of the electron band. The group also intends to investigate the quantum Wigner crystal formation in these ultra-clean systems as a direct consequence of this effect.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

自1911年超导电性被发现以来，建造室温超导体一直是人们的梦想。在相当长的一段时间内，观察到超导性的最高温度保持在23K(或-250摄氏度)；然而，在1986年，人们发现了高温超导体，其超导性在高压下最高可达138K(或-135摄氏度)，最近甚至高达203K(-70摄氏度)。目前，室温超导最有希望的候选材料是所谓的平带材料(即电子的能量在一定动量范围内不依赖于其动量的材料)。PI和他的团队最近在硅-锗量子阱中发现了这种行为，并正在对这种材料进行研究。拟议的活动提供了独特的机会，在当今能力的前沿培训学生掌握新技术。东北大学以其标志性的合作学习(co-op)教育而闻名，这种教育为学生提供了在学习期间进行动手体验学习的机会。在这个项目中，PI在他的实验室培养本科生和研究生方面有着显著的记录。技术摘要拟议的工作是一项实验工作，目的是明确地建立二维电子系统中的电子能带扁平化，这可能对构建室温超导至关重要。该团队打算研究由皮？S小组开发的质量前所未有的硅-锗量子阱，以及质量相当的氧化锌基异质结构。过去，Pi的团队通过输运方法观察到了硅-锗量子阱中的能带平坦。然而，热力学特性，如电子的光谱，只有通过热力学测量才能可靠地获得。Pi和他的团队打算使用东北大学Pi？S实验室已有的技术来测量二维系统中电子的热力学磁化和热电势。第一种方法得到电子的能量平均有效质量；第二种方法得到费米能级上的有效质量。在极低的电子密度极限下，能量平均质量的饱和和费米能级质量的发散是电子带扁平的标志。该小组还打算调查这些超清洁系统中量子维格纳晶体的形成，作为这种影响的直接结果。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Band Flattening and Landau Level Merging in Strongly-Correlated Two-Dimensional Electron Systems

强相关二维电子系统中的能带展平和朗道能级合并

• DOI: 10.1134/s0021364022601257
• 发表时间: 2022
• 期刊: JETP Letters
• 影响因子: 1.3
• 作者: Dolgopolov, V. T.;Melnikov, M. Yu.;Shashkin, A. A.;Kravchenko, S. V.
• 通讯作者: Kravchenko, S. V.

Manifestation of strong correlations in transport in ultraclean SiGe/Si/SiGe quantum wells

超净 SiGe/Si/SiGe 量子阱中输运强相关性的表现

• DOI: 10.1103/physrevb.102.081119
• 发表时间: 2020
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Shashkin, A. A.;Melnikov, M. Yu.;Dolgopolov, V. T.;Radonjić, M. M.;Dobrosavljević, V.;Huang, S.-H.;Liu, C. W.;Zhu, Amy Y.;Kravchenko, S. V.
• 通讯作者: Kravchenko, S. V.

Noise signal as input data in self-organized neural networks

噪声信号作为自组织神经网络中的输入数据

• DOI: 10.1063/10.0010439
• 发表时间: 2022
• 期刊: Low Temperature Physics
• 影响因子: 0.8
• 作者: Kagalovsky, V.;Nemirovsky, D.;Kravchenko, S. V.
• 通讯作者: Kravchenko, S. V.

Hartree-Fock description of a Wigner crystal in two dimensions

二维维格纳晶体的 Hartree-Fock 描述

• DOI: 10.1016/j.physe.2020.114016
• 发表时间: 2020
• 期刊: Physica E: Low-dimensional Systems and Nanostructures
• 作者: Kagalovsky, V.;Kravchenko, S.V.;Nemirovsky, D.
• 通讯作者: Nemirovsky, D.