Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session C06: CMP + Materials 5: Light Matter Interaction |
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Chair: Alejandro Manjavacas, University of New Mexico Room: CSC 210 |
Friday, October 12, 2018 10:45AM - 11:09AM |
C06.00001: Attosecond Carrier Dynamics in Layered and Quasi-2D Semiconductors Invited Speaker: Oliver L.A. Monti 2D and quasi-2D materials have unique electronic properties due to quantum confinement effects, broken symmetries and the layered crystal structure. Some of these aspects have been investigated in some detail in the steady-state regime, but their impact on quasiparticle and carrier dynamics is at present unclear. Relevant time-scales extend from picoseconds to the inherent electronic time-scales in the attosecond regime. In this talk I will demonstrate how the full 3D crystal of a layered material behaves as a 2D material on fs and sub-fs time-scales. I will then show how the electronic structure of MoS2 as a paradigmatic 2D material can be drastically renormalized, pushing carrier dynamics into the regime of 100 attoseconds. Reasons for this dramatic change will be explored, and implications for the design of optoelectronic and spintronic devices based on layered materials will be discussed. |
Friday, October 12, 2018 11:09AM - 11:21AM |
C06.00002: Intersubband Optical Transitions in Ultra-Wide Bandgap Quantum Well Structures Joseph Lyman, Sriram Krishnamoorthy Nanoscale quantum structures form the basis for several technological breakthroughs such as light emitting diodes and night vision devices. In this work, we theoretically explore the optical intersubband transitions in ultra-wide band gap Gallium Oxide/ Aluminum Gallium Oxide heterostructures for infrared detection and resonant tunneling effects. Gallium Oxide is an emerging ultra-wide band gap material with a range of potential applications in electronics and optoelectronics. The main advantage of this material system stems from the availability of large area high quality bulk substrates grown using potentially inexpensive melt-based techniques. The other major advantage of beta-phase Gallium Oxide is the absence of spontaneous and piezoelectric polarization. In this work, we exploit the lack of polarization to engineer intersubband optical transitions in quantum well structures. Energy band diagrams and wavefunction solutions of quantum wells are obtained using a Schrödinger -Poisson solver. Optical transition rates are numerically estimated using fermi golden rule and overlap integrals. This theoretical work is a first step towards exploring Oxide heterostructures for high performance infrared devices and resonant tunneling diodes. |
Friday, October 12, 2018 11:21AM - 11:33AM |
C06.00003: Finding the optical constants of zinc arsenide (Zn3As2) via spectroscopic ellipsometry J Colter Stewart, Micah N Shelley, John S Colton, David D Allred Zinc oxide is a wide band gap semiconductor with the potential to supplement gallium nitride for violet and UV optoelectronic applications. Renlund et al. have fabricated stable p-type zinc oxide material through magnetron sputtering deposition in oxygen onto a zinc arsenide (Zn3As2) layer. Understanding the thickness and optical properties of the zinc arsenide layer is critical in controlling this process. We report some success using spectroscopic ellipsometry to determine the thickness of evaporated zinc arsenide layers. Determining the optical constants of this layer has been more challenging. We will discuss these difficulties, as well as potential solutions. |
Friday, October 12, 2018 11:33AM - 11:45AM |
C06.00004: Terahertz Spectroscopy of Excitons in Metallic Single-Wall Carbon Nanotubes Henry V Wladkowski, Shashank R Nandyala, Jeffrey A Fagan, Jon M Pikal, William D Rice Optically generated, Coulombically bound electron-hole pairs, known as excitons, are rarely observed in metals due to strong electrostatic screening. In quantum-confined systems, such as one-dimensional single-wall carbon nanotubes (SWCNTs), screening effects are suppressed giving rise to an exciton-dominated optical spectra for both semiconductors and metals. Despite interest in many-body effects in excitons, the formation dynamics and internal energy structure of these excitons in low-dimensional metallic environments remain unexplored. In this work, we use aqueous two-phase extraction to produce high-purity, single-chirality metallic SWCNTs on a macroscopic scale. Additionally, we develop a unique polymer matrix, transparent in both visible and terahertz regimes, which maintains nanotube individualization across a broad temperature range. Finally, we use our recently built time-domain terahertz spectroscopy system to probe the conductivity and plasmon edge of high-purity, individualized metallic SWCNTs. This on-going work is an important first step towards understanding exciton behavior in one-dimensional metals. |
Friday, October 12, 2018 11:45AM - 11:57AM |
C06.00005: Optically generated spin currents in Pt/magnetic insulator structures Joseph R Murphy, Subash Kattel, Jinjun Ding, Tao Liu, Mingzhong Wu, William D Rice The generation and detection of pure spin current provides a pathway for solid-state devices to avoid Joule heating losses created in electric current architectures. Despite the promise of loss-free, spin-based devices, integrating spin current technology into real-world applications has proven difficult. Here, we use a Pt/YIG bilayer device to detect light from 390 to 2200 nm using the spin Seebeck effect. We find that the nanometer-thick platinum layer is crucial for both spin current generation and detection. Using a phase-sensitive, field-modulation technique, we determine the gradient across the YIG, ∇T, create by optical illumination, I, to be ∇T/I = 0.0975 °C·m/W. This work reveals the possibility of using spin current generation and detection for broadband light detection devices. |
Friday, October 12, 2018 11:57AM - 12:09PM |
C06.00006: Photochemistry and other applications of diamond Anna Zaniewski, Tirzah Fougner, Holly Johnson, Jonathon Barkl, Franz Koeck, Robert J Nemanich Diamond is a remarkable material for next-generation electronics and photochemistry applications. The electron affinity of diamond surfaces with H, O, or F termination varies by an astounding 3.5 eV, with hydrogen terminated diamond even possessing a negative electron affinity, meaning that its conduction band minimum lies above the vacuum. Under vacuum, n-type nanocrystalline diamond shows the lowest photo-threshold of any non-cesiated material at 1.5eV. In this project, photostimulated diamond in water is studied for its potential to produce solvated electrons, which can in turn be used for reducing molecules such as N2 or CO2. Other applications of diamond electronics may be discussed if time permits. |
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