Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S27: Photon and Electron Transport |
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Sponsoring Units: FIAP Room: 290 |
Thursday, March 16, 2017 11:15AM - 11:27AM |
S27.00001: Critical Dispersion-Theory Tests of Silicon's IR Refractive Index William Karstens, D. Y. Smith Silicon strongly absorbs both visible and UV light, but is highly transparent in the IR. Hence, it is a common choice for infrared windows and lenses. However, optical design is hindered by literature index values that disagree by up to 1{\%}. In contrast optical-glass indices are known to 0.01{\%} or better. The most widely available silicon IR indices are based on bulk measurements using either Snell's-Law refraction by a prism or channel-spectra interference of front- and backsurface reflections from a planar sample. To test the physical acceptability of these data, we have developed criteria based on a Taylor expansion of the Kramers-Kronig relation for the index at energies below strong inter-band transitions. These tests require that the coefficients of the series in powers of energy squared must be positive within the region of transparency. This is satisfied by essentially all prism measurements; their small scatter arises primarily from impurities and doping. In contrast, channel-spectra data fail in the second and third coefficients. A review of the experimental analysis indicates three problems besides purity: incorrect channel number arising from a channel-spectra model that neglects spectrum distortion by the weak lattice absorption; use of a series expansion of mixed parity in photon energy to describe the even-parity index; and use of an incorrect absorption energy in the Li-Sellmeier dispersion formula. Recommendations for IR index values for pure silicon will be discussed. [Preview Abstract] |
(Author Not Attending)
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S27.00002: High Peak Field THz Pump-THz Probe Spectroscopy in Two Dimensional Electron Gas Systems A. G. Linn, B. Barman, S. A. McGill, D. Karaiskaj, J. L. Reno, D. J. Hilton We used the technique of THz pump-THz probe spectroscopy to study carrier dynamics in Two Dimensional Electron Gas (2-DEG) systems.(\textbf{1}) Single cycle THz pulses were generated via femtosecond laser pump pulse-front tilting for optical rectification in a LiNbO3 crystal.(\textbf{2}) Contrary to optical excitation, THz excitation only results in intra-band transitions, eliminating direct generation of electrons and holes, leading to an increase in the carrier scattering rate. Using this method, we investigated free carrier absorption as well as relaxation of excited carriers back into the $\Gamma $ valley in GaAs 2-DEG samples of varying well widths. (\textbf{1}) Matthias C. Hoffmann et al., J. Opt. Soc. Am. B 26 (9), A29 (2009). (\textbf{2}) H. Hirori et al., Applied Physics Letters 98 (9), 091106 (2011). [Preview Abstract] |
Thursday, March 16, 2017 11:39AM - 11:51AM |
S27.00003: Two-photon Cyclotron Absorption in the Microwave-Induced Zero States Jie Zhang, RuiRui Du, Lorren Pfeiffer, Ken West Utilizing a microwave reflection spectroscopy we simultaneously measure cyclotron absorption and electrical transport in zero-resistance state. Two-photon processes are observed in the cyclotron absorption and transport measurement with different power dependence and plasmon coupling. Surprisingly, two-photon cyclotron transitions account for the major absorption peak regardless of microwave power. We attribute the far-fields peaks in the photoresistance spectra to a multiphoton inelastic mechanism, which relaxes mainly by impurity scattering. We interpret the observation as that the two-photon cyclotron absorption arises from stepwise single photon transitions and relaxes mainly through phonon coupling. These two distinct mechanisms coexist in the same cyclotron resonance process. Work at Rice were founded by NSF DMR-1508644 and Welch grant C-1682. [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:03PM |
S27.00004: Light Propagation Through Transition Metal Dichalcogenides Christopher Stevens, Jagannath Paul, Haoxiang Zhang, Andreas Stier, Denis Karaiskaj C.E.STEVENS,J.PAUL,H.ZHANG, Dept. of Physics, University of South Florida, Tampa, Florida 33620, USA. A.V.STIER, National High Magnetic Field Laboratory, Los Alamos, New Mexico 87545, D. KARAISKAJ, Dept. of Physics, University of South Florida, Tampa, Florida 33620, USA. -- Using broadband light, the propagation of light through MoSe2 and WSe2 was investigated. Measuring the optical density for samples with different number of layers, we found that these values differ from what the Beer-Lambert Law predicts. The results were also modeled theoretically according to an effective two-band model. [Preview Abstract] |
Thursday, March 16, 2017 12:03PM - 12:15PM |
S27.00005: Effect of strain on the optical and mechanical properties of $\beta-\text{Ga}_2\text{O}_3$ Marco Santia, John Albrecht, Nandan Tandon Strain-induced modulation of the dielectric response in a material can result in large birefringence effects that are difficult to characterize experimentally. This elasto-optic (or photoelastic) phenomena complicates design of optoelectronic devices where the behavior of the dielectric function must be well understood, which has been the focus of recent works on $\beta-\text{Ga}_2\text{O}_3$-based devices. The monoclinic geometry of this material further complicates characterizing the response to strain during both fabrication and in device design. Here we present a first principles, density-functional perturbation theory (DFPT) calculation on bulk $\beta-\text{Ga}_2\text{O}_3$ for the elasto-optic tensor by solving the self-consistent Sternheimer equation in the spectral range (up to $9\,\text{eV}$) . The elastic stiffness tensor is also computed to determine the importance of purely geometric contributions to the strain response. We also discuss the implications on the magnitude and directions of birefringence that can arise. [Preview Abstract] |
Thursday, March 16, 2017 12:15PM - 12:27PM |
S27.00006: Study of the angular phase shift in the polarization angle dependence of the microwave induced magnetoresistance oscillations Han-Chun Liu, Rasanga Samaraweera, Ramesh Mani, Christian Reichl, Werner Wegscheider We examine the microwave frequency($f)$-variation of the angular-phase-shift, $\theta_{0}$, observed in the polarization-angle-dependence of the microwave-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs two-dimensional electron system[1][2]. By fitting the diagonal resistance R$_{xx}$ vs. $\theta_{0}$ plots to an empirical cosine square law, we extract the $\theta_{0}$ and trace its quasi-continuous variation with $f$. The results suggest that the overall average of $\theta_{0}$ extracted from Hall bar device sections with length-to-width ratio L/W $=$ 1 and L/W $=$ 2 is the same. We compare the observations with expectations arising from the ``pondermotive force'' theory for the microwave radiation-induced transport phenomena. [1] R. G. Mani et al., Phys. Rev. B 84, 085308 (2011). [2] A. N. Ramanayaka et al., Phys. Rev. B 85, 205315 (2012). [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 12:39PM |
S27.00007: Light-effect transistor (LET) with multiple independent gating controls for optical logic gates and optical amplification Jason Marmon, Satish Rai, Kai Wang, Weilie Zhou, Yong Zhang The pathway for CMOS technology beyond the 5-nm technology node remains unclear for both physical and technological reasons. A new transistor paradigm is required. A LET (Marmon et. al., Front. Phys. 2016, 4, No. 8) offers electronic-optical hybridization at the component level, and is capable of continuing Moore's law to the quantum scale. A LET overcomes a FET's fabrication complexity, e.g., physical gate and doping, by employing optical gating and photoconductivity, while multiple independent, optical gates readily realize unique functionalities. We report LET device characteristics and novel digital and analog applications, such as optical logic gates and optical amplification. Prototype CdSe-nanowire-based LETs, incorporating an M-S-M structure, show output and transfer characteristics resembling advanced FETs, e.g., on/off ratios up to 10$^{\mathrm{6}}$~with a source-drain voltage of 1.43V, gate-power of 260nW, and a subthreshold swing of 0.3nW/decade (excluding losses). A LET has potential for high-switching (THz) speeds and extremely low-switching energies (aJ) in the ballistic transport region. Our work offers new electronic-optical integration strategies for high speed and low energy computing approaches, which could potentially be extended to other materials and devices. [Preview Abstract] |
Thursday, March 16, 2017 12:39PM - 12:51PM |
S27.00008: Impact of Alloy Fluctuations on Radiative and Auger Recombination in InGaN Quantum Wells Christina Jones, Chu-hsiang Teng, Qimin Yan, Pei-cheng Ku, Emmanouil Kioupakis Light-emitting diodes (LEDs) based on indium gallium nitride (InGaN) are important for efficient solid-state lighting (2014 Nobel Prize in Physics). Despite its many successes, InGaN suffers from issues that reduce the efficiency of devices at high power, such as the green gap and efficiency droop. The origin of the droop has been attributed to Auger recombination, mediated by carrier scattering due to phonons and alloy disorder. Additionally, InGaN exhibits atomic-scale composition fluctuations that localize carriers and may affect the efficiency. In this work, we study the effect of local composition fluctuations on the radiative recombination rate, Auger recombination rate, and efficiency of InGaN/GaN quantum wells. We apply k.p calculations to simulate band edges and wave functions of quantum wells with fluctuating alloy distributions based on atom probe tomography data, and we evaluate double and triple overlaps of electron and hole wave functions. We compare results for quantum wells with fluctuating alloy distributions to those with uniform alloy compositions and to published work. Our results demonstrate that alloy-composition fluctuations aggravate the efficiency-droop and green-gap problems and further reduce LED efficiency at high power. [Preview Abstract] |
Thursday, March 16, 2017 12:51PM - 1:03PM |
S27.00009: Phosphorescence from organic metal-free materials: Simulation and experimental studies Hossein Hashemi, Jaehun Jung, Jinsang Kim, John Kieffer The desire for green technology has touched all aspects of our lives, including the way we light our homes. Using density functional theory (DFT) and time-dependent DFT (TDDDFT) calculations, we have investigated the photophysical properties of a series of bromofluorene (BrFl) derivatives as potential candidates for a new generation of OLEDS. The calculated absorption and~emission properties of the series as well as phosphorescence quantum yield are in good agreement with the available experimental data. The underlying phosphorescence mechanisms are explored through calculations of the~spin orbit coupling values, the S $\to $ T intersystem-crossing matrix elements and the crossing rate constants. In addition, we calculate both the radiative and non-radiative decay rates of the lowest triplet state (T$_{1})$ for all the BrFl derivatives. Our studies suggest that functional group modification can control not only phosphorescence properties and emission color but also brightness. Our findings demonstrate how computation can be effectively used for the predictive design of organic materials in lighting devices. [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:15PM |
S27.00010: Structural and electronic properties of BInGaN alloys lattice-matched to GaN Logan Williams, Emmanouil Kioupakis Blue LEDs based on InGaN alloys find important commercial applications for solid-state lighting and displays (Nobel Prize in Physics, 2014). However, the constraints imposed by currently used materials reduce the efficiency of nitride LEDs at high power and longer wavelengths. In particular, the large lattice mismatch between InN and GaN causes a strong strain on InGaN quantum wells grown epitaxially on GaN, which in turn limits the thickness of high-crystalline-quality quantum wells that can be grown. Narrow quantum wells are linked to high operating carrier densities and thus a significant role of nonradiative Auger carrier recombination during device operation, which suppresses the efficiency. In this work, we investigate the effect of Boron incorporation into InGaN alloys on the structural and electronic properties. Boron is a smaller atom that GaN, and yields BInGaN alloys that are lattice-matched to GaN, while enabling the tuning of the band gap in the visible range. Our results establish the connection between the BInGaN alloy composition and the LED emission wavelength for alloys that are lattice-matched to GaN. [Preview Abstract] |
Thursday, March 16, 2017 1:15PM - 1:27PM |
S27.00011: Electron quantum optics as signal processing Benjamin Roussel, Cl\'ement Cabart, Pascal Degiovanni Electron quantum optics is an emerging field aiming at understanding quantum transport using ideas from photon quantum optics [Annalen der Physik, {\bf 526}, 1 (2014)]. The key question in electron quantum optics is to determine which single-electron and more generally many-electron wavefunctions are propagating in the conductor. This is encoded within the electronic coherences defined similarily to the Glauber correlation function of order $n$ giving access to the result of every $n$-particle interferometry experiments. This raises the question of the best elementary signals describing the electronic coherences of a periodically driven electronic source [arXiv:1610.02086]. In this work, we introduce the spectral decomposition of the electron and hole parts of the first-order coherence. From this, we compute the best elementary signals describing a periodic source. Whenever interactions can be neglected, we can reconstruct the whole many-body state. We then define a many-body notion of entanglement spectrum giving a many-body criterion for pure electron or hole emission relevant when considering a driven Ohmic contact or the mesoscopic capacitor. This work is a first step towards the development of quantum signal processing techniques in electron quantum optics. [Preview Abstract] |
Thursday, March 16, 2017 1:27PM - 1:39PM |
S27.00012: Physical properties of the wide band gap II-IV nitride MgSiN$_{2}$ Mikael R{\aa}sander, James Quirk, Michelle Moram The Group II-IV nitride semiconductors are emerging as promising alternatives to III-nitrides in ultraviolet LED applications. These materials have wurtzite-derived orthorhombic crystal structures and can be obtained by substituting pairs of Group III atoms in a III-nitride for a single Group II atom and a single Group IV atom. Here we will focus on MgSiN$_{2}$, which is the equivalent II-IV nitride to wurtzite AlN. A detailed comparison of the properties obtained by first principles calculations and experiment of these two systems will be performed. It will be shown that MgSiN$_{2}$ has a large indirect band gap of similar size to the direct band gap of AlN, while having a crystal size which is intermediate between AlN and GaN.\footnote{J. B. Quirk, M. R{\aa}sander, C. M. McGilvery, R. Palgrave and M. A. Moram, Appl. Phys. Lett. 105, 112108 (2014), M. R{\aa}sander and M. A. Moram, Mater. Res. Express 3, 85902 (2016). } MgSiN$_{2}$ should therefore facilitate better lattice matching during film growth compared to AlN, and therefore constitutes a good candidate material to be used in novel high efficiency UV-LEDs. [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 1:51PM |
S27.00013: Two electron coherence in electron quantum optics Pascal Degiovanni, Clement Cabart, Benjamin Roussel, Etienne Thibierge, Dario Ferraro, Arthur Marguerite, Gwendal F\ève Engineering and studying few-electron states in ballistic conductors is a key step towards understanding the emergence of many-body physics and entanglement in quantum electronic systems [Ann. Phys. (Berlin) {\bf 526}, 1 (2014)]. In this talk, we will discuss intrinsic two electron coherence of an electronic source in quantum Hall edge channels and relate it to two-electron wave functions. Inspired by photon quantum optics we will relate it to the current noise in an Hanbury Brown and Twiss interferometer thus relating electronic coherences to the quantum fluctuations of the radiation emitted by the conductor. We will show how it can be measured using two particle interferences in Franson-like interferometers thus realizing a two-particle analog of a Mach-Zehnder interferometer [Phys. Rev.B {\bf 113}, 081302(R) 2016]. [Preview Abstract] |
Thursday, March 16, 2017 1:51PM - 2:03PM |
S27.00014: Vertical cavity surface emitting lasers from all-inorganic perovskite quantum dots Handong Sun, Yue Wang, Xiaoming Li, Haibo Zeng We report the breakthrough in realizing the challenging while practically desirable vertical cavity surface emitting lasers (VCSELs) based on the CsPbX3 inorganic perovskite nanocrystals (IPNCs). These laser devices feature record low threshold (9 \textmu J/cm2), unidirectional output (beam divergence of \textasciitilde 3.6\textordmasculine ) and superb stability. We show that both single-mode and multimode lasing operation are achievable in the device. In contrast to traditional metal chacogenide colloidal quantum dots based lasers where the pump thresholds for the green and blue wavelengths are typically much higher than that of the red, these CsPbX3 IPNC-VCSEL devices are able to lase with comparable thresholds across the whole visible spectral range, which is appealing for achieving single source-pumped full-color lasers. We further reveal that these lasers can operate in quasi-steady state regime, which is very practical and cost-effective. Given the facile solution processibility, our CsPbX3 IPNC-VCSEL devices may hold great potential in developing low-cost yet high-performance lasers, promising in revolutionizing the vacuum-based epitaxial semiconductor lasers. [Preview Abstract] |
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