Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X11: Transport in Nanostructures -- Nanoscale Transport IIFocus
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Sponsoring Units: DMP DCMP Chair: Xuan Gao, Case Western Reserve University Room: BCEC 152 |
Friday, March 8, 2019 8:00AM - 8:12AM |
X11.00001: Super-geometric transverse electron focusing on the hexagonal Fermi surface of PdCoO2 Philip Moll, Maja D Bachmann, Aaron Sharpe, Arthur Barnard, Markus Koenig, Carsten Putzke, Seunghyun Khim, Andrew Mackenzie, David Goldhaber-Gordon Single crystals of PdCoO2 can be easily synthesized at remarkably high quality. At low temperatures, the mean-free-path of this most conductive oxide exceeds 20μm, reflected by its ultra-low residual resistivity of 8 nΩcm. This high conductivity gives rise to different transport regimes, spanning from ballistic transport to hydrodynamic transport regimes. Its ballsitic transport is highly unusual, owing to its peculiar Fermi surface resembling an almost perfect hexagon. We fabricate ballistic structures for transverse electron focusing from as-grown single crystals via focused ion beam machining, and demonstrate magnetic focusing up to 20μm. Compared to typically studied materials with circular Fermi surfaces, the transverse focusing amplitude is strongly enhanced owing to its large parallel sections. We demonstrate this focusing enhancement experimentally, and corroborate it by transport simulations. |
Friday, March 8, 2019 8:12AM - 8:24AM |
X11.00002: Direct Growth of Vertically Aligned Carbon Nanotube Arrays on Stainless Steel and Their Field Emission Properties Arun Thapa, Wenzhi Li We report the growth of VACNT arrays on stainless steel (SS) via dc plasma enhanced chemical vapor deposition without the use of a metal catalyst layer. TEM and AFM examinations revealed the occurrence of nano-hills formed on the SS surface during the heating process in an NH3 environment, which is a critical step for the uniform growth of VACNTs. The particles on the tips of most of the VACNTs were found to be single crystalline Fe metal, although a few other VACNTs were found to have alloy of Fe, Ni, Mn, and Cr at their tips. Field emission (FE) performance of a dense array of VACNTs was enhanced by changing the array morphology through a simple water treatment process. The FE performance was further enhanced by coating the exterior of CNTs with a layer of crystalline SnO2 nanoparticles of 4.18 nm in diameter. The enhancement of FE performance was ascribed to the morphological change and mechanical strength reinforcement of VACNTs by the SnO2 coating process. The characteristic features of the sample as the conductive substrate, ohmic contact between the VACNTs and the substrate, and bundled morphology resulted in a lower turn-on and threshold electric field, higher field enhancement, and excellent emission stability. |
Friday, March 8, 2019 8:24AM - 8:36AM |
X11.00003: The connection between enhanced phonon-exciton interaction next to localization centers and photoluminescence of few-body complexes in tungsten-based transition metal dichalcogenide monolayers. Dinh Van Tuan, Hanan Dery Photoluminescence (PL) experiments in WSe2 show that the neutral-exciton peak X0 in the charge-neutral regime is often accompanied by additional lower-energy peak. The spectral position of the peak is below X0 by one phonon energy. Recently, several groups reported on trion-exciton complexes in encapsulated WSe2 [1,2,3,4,5], where once again, their PL spectra reveal that the peak attributed to the five-particle complex is one phonon energy below that of the biexciton. We show that these PL peaks stem from phonon-assisted recombination of excitons or biexcitons next to localized electrons (i.e., these are not real trions or trion-exciton complexes that can diffuse in the monolayer). We explain why the proposed PL mechanism is prevalent in these monolayers while being absent in absorption-type experiments [6], showing that it supports the observed PL dependences on temperature and background charge density. |
Friday, March 8, 2019 8:36AM - 8:48AM |
X11.00004: ABSTRACT WITHDRAWN (MAR19-3101056_02_19_2020)
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Friday, March 8, 2019 8:48AM - 9:00AM |
X11.00005: Title: Refrigeration and thermometry for millikelvin and sub-millikelvin nanoelectronics. Joshua Chawner, Ian Bradley, Antony Guénault, David Gunnarsson, Richard Haley, Alexander Jones, Yuri Pashkin, Jari Penttilä, Jonathan Prance, Mika Prunnila, Leif Roschier Cooling electrons in a nanoelectronic device to a few milikelvin, and further into the microkelvin regime, is a longstanding challenge. Weak electron-phonon coupling at low temperatures creates a bottleneck in traditional cooling techniques [1]. Here we will present our approach to solving the problem: nuclear demagnetization refrigeration of on-chip copper to directly cool the electrons without intervening phonons [2]. Our method has achieved a base electron temperature below 1.3 mK, held for several 1000s. On-chip refrigeration could potentially provide improvements in the operation of quantum simulators, computers and metrology standards, and open a new regime for the study of electron transport in nanostructures and 2D materials. However, it will be necessary to couple the copper refrigerant to the system of interest and to employ non-invasive thermometry techniques. We will discuss our progress towards these goals, including the development of a single-electron thermometer that is measured by RF reflectometry and does not require galvanic connection between the cooled electron gas and the outside world. |
Friday, March 8, 2019 9:00AM - 9:12AM |
X11.00006: Modeling transport in phosphorus δ-doped silicon tunnel junctions Leon Maurer, Michael Marshall, DeAnna Campbell, Lisa A Tracy, Tzu-Ming Lu, Daniel Ward, Shashank Misra Electrical devices based on Si:P δ layers can be fabricated with atomic precision, which could allow for the fabrication of high-efficiency tunneling field effect transistors (TFETs). While great strides have been made in fabricating nanoelectronics from Si:P δ layers, there is little agreement about the electronic structure of the Si:P δ layers. Furthermore, the transport properties of only a few devices have been modeled. We use a scalable model to study transport in nanoscale tunnel junctions made from Si:P δ layers, and we show that the transport properties of tunnel junctions can provide insight into the electronic structure of Si:P δ layers. We also compare our model to experimental results and find good agreement. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X11.00007: Effect of electron-phonon interaction on the opto-electronic properties of semiconducting nanoparticles Han Yang, Marco Govoni, Giulia Galli We report on the impact of electron-phonon coupling on the opto-electronic properties of semiconducting nanoparticles. We used a newly developed first-principle method [1] based on many-body-perturbation-theory, which efficiently combines electron-electron and electron-phonon interaction without explicitly evaluating virtual electronic orbitals. The method is implemented in the WEST code [2]. In particular we discuss carbon-based nanoparticles and chalcogenide nanostructures. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X11.00008: Electronic noise due to temperature differences in atomic-scale junctions: beyond standard thermal and shot noises Ofir Shein-Lumbroso, Lena Simine, Abraham Nitzan, Dvira Segal, Oren Tal Since the discovery of electronic thermal and shot noise almost a century ago, these two forms of fundamental electronic noise have had an enormous impact on science and technology. Here, we report on a new version of electronic noise that is generated by temperature differences across nanoscale conductors, which we term ‘delta-T noise’1. We experimentally demonstrate this noise in atomic and molecular junctions, and analyze it theoretically using the Landauer formalism. The delta-T noise reveals a peculiar combination of characteristics that makes it different from the known thermal noise and voltage-activated shot noise. This noise can be used to detect temperature differences across nanoscale conductors without the need for fabricating sophisticated local probes. Furthermore, delta-T noise should be considered when designing modern nanoscale electronics, since temperature gradients are often generated unintentionally across electronic components. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X11.00009: Surface Plasmon Polaritons in Chalcogenides Cigdem Ozsoy Keskinbora, Kundan Chaudhary, Michele Tamagnone, Yunbo Ou, Aravind Devarakonda, Takehito Suzuki, Joseph Checkelsky, Jagadeesh Moodera, Federico Capasso, David Bell The surface plasmon polaritons is a highly investigated field of research due to their high potential applications for sensors, information technologies, high resolution imaging, to name a few. These collective electron oscillations are common at metal dielectric interfaces. However, they also exist in highly doped semiconductors, conducting oxide systems, and in many other systems with high carrier mobility. This poses the question of whether such resonances can be observed at the insulator interfaces with these novel materials. Chalcogenides, the general name of sulfides, selenides, tellurides can show highly anisotropic crystal structures, that gives them exotic properties such as topological surface state, superconductivity or negative dielectric permittivity. It was shown that Bi2Se3 supports Dirac plasmons, but the Dirac state is not the only reason for the existence of plasmon resonance in Bi2Se3. This material also has highly anisotropic dielectric properties allowing surface plasmon excitations. It is not the only chalcogenide system that can support them. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X11.00010: Room Temperature Phonon Focusing As a Tool for Tuning Thermal Conductivity in Nanostructured Materials Giuseppe Romano
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Friday, March 8, 2019 10:00AM - 10:12AM |
X11.00011: Vertical p-n junction of a thermoelectric material investigated using photoemission technique Jieun Lee, Jinwoong Hwang, Minhee Kang, Kyoo Kim, Hyejin Ryu, Shujie Tang, Sunglae Cho, Sung-Kwan Mo, Ho-soon Yang, Choongyu Hwang The thermoelectric materials can generate electricity out of heat when they form a p-n junction, connected to an electric circuit. Typically, such a junction is made of two pieces of a thermoelectric material that are doped by electrons and holes, respectively, and then put together. Here we report one of the plausible ways to prepare the p-n junction via the experimental investigation of the electron band structure of a thermoelectric material using photoemission technique. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X11.00012: One-Dimensional Atomic Tellurium Chains in Boron Nitride Nanotubes: Synthesis and Devices Pai-Ying Liao, Jingkai Qin, Mengwei Si, Siqi Zhang, Yoke Khin Yap, Peide (Peter) Ye Tellurium has a unique one-dimensional (1D) helical chain crystal structure. The adjacent tellurium atoms in a single chain are covalently bonded, and different chains interact with each other by van der Waals force to form planar and bulk crystal. As a narrow-bandgap p-type semiconductor, bulk tellurium has a direct bandgap of ~0.35 eV. Here, 1D atomic tellurium chains were grown inside the boron nitride nanotubes (BNNTs) whose inner diameter was only a few nanometers. 1D tellurium crystal was synthesized and grew along the direction of BNNTs due to the natural confinement of the BNNT physical structure. Raman spectroscopy and energy-dispersive X-ray spectroscopy (EDX) were utilized to characterize the tellurium crystal structure and guaranteed the high quality of the Te-BNNT samples. The electrical properties of Te-BNNT devices were studied by current-voltage measurement. The devices were fabricated by transferring Te-BNNTs onto SiO2/p++ Si substrate, Ar-SF6 dry etching, and deposition of metal electrodes on top of the nanotubes. The realization of BNNTs-capsulated tellurium chains enhanced the current capacity of tellurium crystal several times compared to bare tellurium nanowires. |
Friday, March 8, 2019 10:24AM - 10:36AM |
X11.00013: Single-molecule rectifiers based on voltage-dependent deformation of molecular orbitals in carbazole oligomers Tatsuhiko Ohto, Ken Albrecht, Ryo Yamada, Keigo Minode, Kimihisa Yamamoto, Hirokazu Tada Current-voltage characteristics of single molecule junctions are governed both by the energy level alignment of molecular orbitals with respect to the Fermi level of the electrodes and by the hybridization of electronic structures at the interface between the molecule and the electrodes. While there have been many studies on tuning the former, only a few works intended to control the latter. In the present study, we demonstrate that molecular junctions based on carbazole oligomers showed a current rectification behavior due to asymmetric-symmetric control of electronic hybridization between the molecule and electrodes at the both terminals. The carbazole oligomers originally showed an asymmetric molecular orbital and, hence, electronic hybridization with the electrodes because of the electric dipole moment. Symmetric electronic hybridization was achieved when the applied electric field between electrodes deformed molecular orbital to be symmetric. This is a novel way to control charge transport in single-molecule junctions (R. Yamada et al., Nanoscale, in press). |
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