Current-Driven Nonequilibrium Electrodynamics and Thermodynamics in Quantum Materials at the Nanoscale

纳米量子材料中电流驱动的非平衡电动力学和热力学

• 批准号: 1904576
• 负责人: Mengkun Liu
• 金额: $ 40万
• 依托单位: SUNY at Stony Brook
• 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: 2019-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904576&HistoricalAwards=false
• 关键词: Current; Driven; Nonequilibrium; Electrodynamics; Thermodynamics

Non-Technical Abstract:Many materials can make the transition from nonconducting (insulator) to conducting (metal) through applied pressure, temperature, or photoexcitation. In certain quantum material systems, this insulator to metal transition can be achieved using very modest electric current or voltage, making potential applications to fast electrical switch, energy-efficient memory or transistor devices possible. To understand the mechanism of current or voltage induced switching, however, is nontrivial. Among many practical obstacles, one major setback is the inability to distinguish between the current-driven nonthermal state and a 'trivial' heat-induced high-temperature phase. Moreover, inhomogeneous strain, defects, and chemical doping add complications, especially when samples approach submicron scale, which is common in modern nano-electronic devices. This research project aims to develop new techniques and establish a coordinated microscopic mapping of the optical and thermal properties of quantum materials during conductivity switching induced by electric current. More specifically, this research provides a quantitative description of the current-driven local variations in optical dielectric function, temperature, and thermal conductivity at characteristic length scales ranging from nanometers to microns, using state-of-the-art scanning probe microscopy and spectroscopy. Based on systematic studies of representative quantum materials such as correlated transition metal oxides with 3d or 4d orbitals, the Principle Investigator will establish an integrated research and education program to explore nonequilibrium states at the nanoscale over a broad infrared to terahertz frequency range. This research also provides sophisticated training to young researchers and a future generation of scientists in a broad range of knowledge. This includes various types of microscopy, spectroscopy, and nanofabrication techniques.Technical Abstract: Quantum materials host a surprisingly diverse set of phase changes when their electrons or lattice are perturbed by various stimuli. By combining the scattering-type scanning near-field optical microscope and scanning thermal microscope into one integrated apparatus, this research studies the current-induced nonequilibrium insulator-to-metal phase transitions in representative quantum materials (e.g. Ca2-xSrxRuO4). The research team will create an experimental routine to distinguish between current-driven and thermal or strain induced phases in bulk single crystals or epitaxial thin films. Dielectric constant, critical current density, nanoscale electrical and heat current transport can be systematically investigated with a spatial resolution smaller than 50 nm. Near-field experiments can be aided with theoretical effort (Boltzman theory) to study nonlocal phenoemon in the proximity of the electrodes at the nanoscale. This work establishes a rigorous procedure to scrutinize the thermal and nonthermal current-driven phase transition in quantum materials. The nanoscale optical and thermal imaging investigation in controlled experimental environments provides a unique platform to systematically study current induced mesoscopic phase transition, separation, electron-lattice correlations and nonlocal effects. The methodology is widely applicable, and the dielectric constant extraction program can be extremely beneficial for the optics community. Research in this area will not only profoundly broaden the fundamental knowledge of topics including Mott physics in transition metal oxides and nonlocal heat transport in nanodevices but will also open new routes to control the intrinsic electronic properties with electric means at the nanoscale.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.

非技术摘要：许多材料可以通过施加压力、温度或光激发从非导电（绝缘体）过渡到导电（金属）。在某些量子材料系统中，这种绝缘体到金属的转变可以使用非常适度的电流或电压来实现，使得快速电开关、节能存储器或晶体管器件的潜在应用成为可能。然而，理解电流或电压感应开关的机制并不容易。在许多实际障碍中，一个主要的挫折是无法区分电流驱动的非热态和“平凡的”热诱导高温相。此外，不均匀的应变、缺陷和化学掺杂增加了复杂性，特别是当样品接近亚微米尺度时，这在现代纳米电子器件中很常见。该研究项目旨在开发新技术，并建立量子材料在电流诱导的电导率切换期间的光学和热学性质的协调微观映射。更具体地说，这项研究提供了一个定量描述的电流驱动的局部变化的光学介电函数，温度和热导率的特征长度范围从纳米到微米，使用国家的最先进的扫描探针显微镜和光谱。基于对具有代表性的量子材料（如具有3d或4d轨道的相关过渡金属氧化物）的系统研究，首席研究员将建立一个综合的研究和教育计划，以探索在宽红外到太赫兹频率范围内的纳米级非平衡态。这项研究还为年轻研究人员和未来一代科学家提供了广泛知识的高级培训。这包括各种类型的显微镜、光谱学和纳米纤维技术。技术摘要： 当量子材料的电子或晶格受到各种刺激的扰动时，它们会发生令人惊讶的各种相变。通过将散射型扫描近场光学显微镜和扫描热显微镜结合在一个集成的装置中，本研究研究了典型量子材料（如Ca 2-xSrxRuO 4）中电流诱导的绝缘体-金属非平衡相变。研究小组将创建一个实验程序，以区分电流驱动和热或应变诱导的阶段，在大块单晶或外延薄膜。介电常数，临界电流密度，纳米级的电流和热流传输可以系统地研究与空间分辨率小于50 nm。近场实验可以借助理论上的努力（玻尔兹曼理论）来研究纳米级电极附近的非局部现象。这项工作建立了一个严格的程序来仔细研究量子材料中的热和非热电流驱动相变。在受控实验环境中的纳米光学和热成像研究提供了一个独特的平台，系统地研究电流诱导的介观相变，分离，电子晶格相关性和非局域效应。该方法是广泛适用的，和介电常数提取程序可以是非常有益的光学社区。这一领域的研究不仅将极大地拓宽过渡金属氧化物中的莫特物理和纳米器件中的非局部热传输等课题的基础知识，而且还将开辟新的途径，以在纳米级用电手段控制固有的电子特性。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

项目成果

Joule heating in Boltzmann theory of metals

玻尔兹曼金属理论中的焦耳热

• DOI: 10.1103/physrevb.102.165134
• 发表时间: 2020
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Allen, Philip B.;Liu, Mengkun
• 通讯作者: Liu, Mengkun

Effect of sample anisotropy on scanning near-field optical microscope images

• DOI: 10.1063/5.0039632
• 发表时间: 2021-02-28
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Chui, S. T.;Chen, Xinzhong;Liu, Mengkun
• 通讯作者: Liu, Mengkun

Validity of Machine Learning in the Quantitative Analysis of Complex Scanning Near-Field Optical Microscopy Signals Using Simulated Data

• DOI: 10.1103/physrevapplied.15.014001
• 发表时间: 2021-01-04
• 期刊: PHYSICAL REVIEW APPLIED
• 影响因子: 4.6
• 作者: Chen, Xinzhong;Ren, Richard;Liu, Mengkun
• 通讯作者: Liu, Mengkun

High-efficiency scattering probe design for s-polarized near-field microscopy

• DOI: 10.35848/1882-0786/abd716
• 发表时间: 2021-01
• 期刊: Applied Physics Express
• 影响因子: 2.3
• 作者: Richard Ren;Xinzhong Chen;Mengkun Liu

Ultrabroadband infrared near-field spectroscopy and imaging of local resonators in percolative gold films

• DOI: 10.1364/josab.36.003315
• 发表时间: 2019-12-01
• 期刊: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
• 影响因子: 1.9
• 作者: Chen, Xinzhong;Zhang, Jiawei;Liu, Mengkun
• 通讯作者: Liu, Mengkun