Quantum Nano-Electro-Mechanical Systems (QNEMS)

量子纳米机电系统(QNEMS)我们的目标是同时了解量子纳米机电系统(QNEMS)的机械和电子性能。为此，我们利用了我们独特的仪器(超低温下的应变和量子传输)和纳米设备(悬浮的低无序2D和1D晶体)。我们将在QNEMS中进行三组实验：(1)介观输运的应变工程：弹道输运、多体相和电子；(2)光-NEMS(NOEMS)：机械共振、光子吸收和热输运的相互作用；(3)可调谐分子尺度的NEMS。第一组目标是2D材料中传输的应变工程。单层和双层石墨烯是弥合目前有限的实验和二维量子输运应变工程先进理论之间的差距的理想体系。我们将对超清洁悬浮石墨烯晶体管施加高达几个百分点的单轴应变，以展示在柔性电子产品中应用的原始(大块)石墨烯中的高开关比晶体管。我们还将利用魔角双层石墨烯(两个石墨烯晶体相互压在一起旋转一度)中的单轴应变来调整其能带结构，并探索其超导相图。我们将开发将三轴应变应用于石墨烯的能力，以创建可调的伪磁场，并实现谷极化电流。第二个轴将探索石墨烯光电异质结(NOEMS)中的光子吸收和热传输。大型(几微米)悬浮器件将通过在氮化硼中的沟槽上方冲压2D晶体来创建。当在悬挂的2D材料下面添加铝反射器时，设备将容纳光电机械腔。利用它们，我们将工程增强2D材料中的光吸收。另一组实验将是同时测量二维材料(如石墨烯和双层石墨烯)的晶格(声子)和电子(载流子)导热系数，以量化电荷载流子和声子之间的能量流动。第三组目标是探索高度可调的近分子规模(~10 nm)的NEMS，由单壁碳纳米管(SWCNTs)和石墨烯中的悬浮量子点(QD)组成。我们建议在单分子尺度和100纳米尺度之间弥合对NEMS的理解鸿沟。我们将测试QNEMS的机械性能的定标极限，并可能应用于质量传感器和射频混频器。我们将研究发生在单分子电子学中的多体量子效应，例如单碳纳米管量子点中的极化子物理。另一个引人入胜的前景是使用10纳米尺度的单壁碳纳米管量子点来制作S-N-S约瑟夫森结。这将使我们能够研究Kondo、Andreev约束态、Shiba态的物理及其相图。

Quantum Nano-Electro-Mechanical Systems (QNEMS) We aim to understand simultaneously the mechanical and electronic capabilities of quantum nano-electro-mechanical systems (QNEMS). To do so, we leverage our unique instrumentation (strain and quantum transport at ultra-low temperatures), and nanodevices (suspended low-disorder 2D and 1D crystals). We will pursue three groups of experiments in QNEMS: (1) Strain-engineering of mesoscopic transport: ballistic transport, many-body phases, and valleytronics, (2) Opto-NEMS (NOEMS): interplays of mechanical resonances, photon absorption, and thermal transport, and (3) Tunable Molecular-scale NEMS. A first cluster of objectives is the strain engineering of transport in 2D materials. Monolayer and bilayer graphene are ideal systems to bridge the gap between the presently limited experiments and advanced theories in strain-engineering of 2D quantum transport. We will apply uniaxial strains up to a few percent to ultra-clean suspended graphene transistors to demonstrate high on/off ratio transistors in pristine (bulk) graphene for applications in flexible electronics. We will also use uniaxial strain in magic-angle bilayer graphene (two graphene crystal stamped on one another with a one degree rotation) to tune its band structure and explore its superconducting phase diagram. We will develop the capability to apply tri-axial strain to graphene to create tunable pseudo-magnetic fields, and achieve valley-polarized currents. A second axis will explore photon absorption and heat transport in graphene opto-electronic heterostructures (NOEMS). Large (several microns) suspended devices will be created by stamping 2D crystals above trenches in boron nitride. When adding aluminum reflectors below the suspended 2D materials, the devices will host opto-electro-mechanical cavities. Using them, we will engineer the enhancement of optical absorption in 2D materials. Another set of experiments will be to measure simultaneously the lattice (phonon) and electron (carrier) heat conductivities of 2D materials such as graphene, and bilayer graphene to quantity the energy flow between the charge carriers and phonons. A third set of objectives is aimed at exploring highly-tunable near-molecular scale (~10-nm) NEMS, consisting of suspended quantum dots (QDs) in single-wall carbon nanotubes (SWCNTs) and graphene. We propose to bridge the gap in the understanding of NEMS between the single-molecule scale and 100-nm scale. We will test the scaling-limit of the mechanical performance of QNEMS, with possible applications as mass sensors and RF mixers. We will study many-body quantum effects taking place in single-molecule electronics such as polaron physics in SWCNT-QDs. Another fascinating prospect is using 10-nm scale SWCNT QDs to make hybrid S-N-S Josephson junction. This will enable us to study the physics of Kondo, Andreev bound states, Shiba states, and their phase diagrams.