Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L33: Quantum Devices and 2D MaterialsFocus
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Sponsoring Units: FIAP Chair: Eui-Hyeok Yang Room: BCEC 204B |
Wednesday, March 6, 2019 11:15AM - 11:27AM |
L33.00001: Quantum Surfing - Pushing a Particle through a Rough Potential Daniel Mark, Samuel F Savitz, Gil Refael Quantum machines rely on our ability to manipulate the motion of electrons. We investigate the transport of particles by a travelling potential pulse in a one-dimensional system with quenched disorder, dissipation, and thermal noise. We simulate finite temperature and dissipation by applying the Schrodinger-Langevin equation to a single-particle hopping model. The transport is understood as a semiclassical Fokker-Planck diffusion process in the pulse frame. The semiclassical behavior arises from decoherence due to the dissipation and thermal noise. We predict that the "surfing length", our measure of transport, is exponential with pulse width. Measurements agree with drift velocities and diffusivities from simulations with a constant DC field, in the regime of high disorder and thermal noise. We also introduce an alternative nonlinear dissipative term which allows for generalization to higher dimensions and many-body systems. |
Wednesday, March 6, 2019 11:27AM - 11:39AM |
L33.00002: Electrical initialization of electron and nuclear spins in a single quantum dot at zero magnetic field Pierre Renucci, Fabian Cadiz, Adbelhak djeffal, Delphine Lagarde, Andrea Balocchi, Bingshan Tao, Bo Xu, shiheng liang, mathieu stoffel, xavier devaux, Henri Jaffres, Jean-Marie George, Michel Hehn, Stephane Mangin, Hélène Carrere, Xavier Marie, Thierry Amand, Xiufeng Han, Zhanguo Wang, Bernhard Urbaszek, Yuan Lu We demonstrate single quantum dot (p-type InGaAs quantum dot) electroluminescence (EL) with a circular polarization degree up to 35% at zero applied magnetic field, proving highly efficient electrical injection of spin polarized electrons [1]. It is achieved thanks to an ultrathin CoFeB electrode presenting Perpendicular Magnetic Anisotropy on top of a spin-LED. In addition, we measure an Overhauser shift of several micro-eV at zero magnetic field for the positively charged exciton (trion X+) EL emission, which changes sign as we reverse the injected electron spin orientation. This is a signature of dynamic polarization of the nuclear spins [1] in the quantum dot induced by the hyperfine interaction with the electrically injected electron spin. Both EL circular polarization and Overhauser shift follow the hysteresis cycle of the magnetic electrode. This study paves the way for electrical initialization of electron and nuclear spins in a single quantum dot without any external magnetic field. [1] F. Cadiz et al, Nano Letters 18 (4), 2381-2386 (2018) |
Wednesday, March 6, 2019 11:39AM - 11:51AM |
L33.00003: Colloidal Quantum Dot Tandem Photovoltaics Employing a Novel Hole-blocking Injection Layer Concept Sue Shi, Yijin Guo, Gillian Hagen, Benjamin A Zank, Alexi C Arango Colloidal quantum dot (CQD) tandem photovoltaics (PV) are of interest as candidates for next-generation PV due to their potential for low-cost fabrication and compatibility with lightweight flexible packaging. In this work, we present a CQD tandem PV device that employs indium tin oxide (ITO) as interconnection layer and a novel injection layer with hole-blocking functionality. A lead sulfide (PbS) CQD heterojunction is formed with C60 in each subcell, yet the traditional BPhen/Ag contact is replaced with ITO. We demonstrate that a hole-blocking injection layer must be inserted between C60 and interconnection layer ITO in order to achieve excellent electrical contact between the two. We obtain a doubling in open-circuit voltage and maintain the high fill factor of the single-junction device. This device structure is particularly suited to multiple-cell tandem PV. |
Wednesday, March 6, 2019 11:51AM - 12:03PM |
L33.00004: 0.7 Anomaly, Spin-Mixing and Emergent Spin Gap in Quantum Point Contacts with Strong Spin-Orbit Interaction Karina Hudson, Ashwin Srinivasan, Olga Goulko, Jarrod Adam, Qingwen WANG, LaReine Yeoh, Oleh Klochan, Ian Farrer, David A Ritchie, Jan Von Delft, Alex R Hamilton Quantum point contacts (QPCs) are 1D charge constrictions where ballistic conductance through the channel is quantised in integer units, with the exception of the 0.7(2e2/h) anomaly. The microscopic origin of the 0.7 anomaly remains contentious after over 20 years of study, and the additional influence of spin-orbit interaction (SOI) is even more poorly understood. |
Wednesday, March 6, 2019 12:03PM - 12:15PM |
L33.00005: Ultrasensitive displacement noise measurement of carbon nanotube mechanical resonators Chandan Samanta, sergio Lucio de Bonis, Carles Flores, Wei Yang, Adrien Noury, Quan Dong, Yong Jin, Adrian Bachtold Mechanical resonators based on a single carbon nanotube are exceptional sensors of mass and force. The force sensitivity in these ultra-light resonators is often limited by the noise in the detection of the vibrations. Here, we report on an ultra-sensitive scheme based on a RLC resonator and a low-temperature amplifier to detect nanotube resonators. These advances in detection allow us to reach 0.5 pm/ displacement sensitivity [1]. Thermal vibrations cooled cryogenically at 300 mK are detected with a signal-to-noise ratio as high as 17 dB. We demonstrate 4.3 zN/ force sensitivity, which is the best force sensitivity achieved thus far with a mechanical resonator. This is an important step towards imaging individual nuclear spins and studying the coupling between mechanical vibrations and electrons in different quantum electron transport regimes. We will also present our recent measurements on the coupling between mechanical vibrations and electrons in the Coulomb blockade regime. |
Wednesday, March 6, 2019 12:15PM - 12:27PM |
L33.00006: Large-area graphene quantized Hall resistance arrays using superconducting interconnections Mattias Kruskopf, Albert Rigosi, Hanbyul Jin, Dinesh Patel, Shamith Payagala, Alireza Panna, Dean G. Jarrett, David B Newell, Randolph E Elmquist Next generation quantum resistance standards based on multiple quantized Hall resistance (QHR) elements will allow tailoring the fundamental value to the needs of a given application. However, scalable resistance networks often suffer from accumulated resistances at metallic interconnections that lead to a deviation from the theoretical value. |
Wednesday, March 6, 2019 12:27PM - 12:39PM |
L33.00007: WITHDRAWN ABSTRACT
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Wednesday, March 6, 2019 12:39PM - 12:51PM |
L33.00008: Effects of Wet Transfer on Photoluminescence of WS2 XIAOTIAN WANG, Kyungnam Kang, Shichen Fu, Kyle Godin, Siwei Chen, Eui-Hyeok Yang Chemical vapor deposition (CVD)-grown transition metal dichalcogenides (TMDs) are often required to be transferred onto another substrate for device applications. The KOH-based wet transfer is the most popular method to transfer TMDs. However, after transfer, PL intensity is heavily quenched due to a combination of trappd water, substrate dope and solvent effects which are introduced during transfer process. |
Wednesday, March 6, 2019 12:51PM - 1:03PM |
L33.00009: Optical verification of H-point exciton in bulk transition metal dichalcogenides So Yeun Kim, Huyen Thi Nguyen, Byung Cheol Park, Tae Won Noh During last decades, transition metal dichalcogenide (TMDC) compounds has been studied extensively. TMDCs provide an excellent platform to investigate many-body physics of exciton, and exciton binding energy increased significantly by reducing thickness. Mostly hydrogen models are used to obtain band gap and exciton binding energy from absoption spectra. On the other hand, recent reports on bulk TMDC claimed an peak previously assigned as n=2 state of A exciton at K-point is not true, but is an independent n=1 exciton arising at H-point [J. Kopaczek et al., Jour. Appl. Phys. 119, 235705 (2016)]. Following the argument, previous method to obtain binding energy of bulk TMDC may be incorrect. To verify the existence of H-point, we performed an ellipsometry measurements and two-dimensional correlation spectroscopy on TMDC compounds. We analyzed thermal sequential order of exciton peaks, which may be used to distinguish exciton states that arise from K-point and H-point. In this work, we will discuss on analysis and possible impact in future studies. |
Wednesday, March 6, 2019 1:03PM - 1:15PM |
L33.00010: Precursor Free Growth of MoS2 Monolayer Devices With Naturally Formed Contacts Thushan Wickramasinghe, Gregory Jensen, Ruhi Thorat, Eric A Stinaff Interest in two dimensional Transition Metal Dichalcogenides (TMDs) has remained robust due to properties such as their direct band gap, large exciton binding energies, sizeable spin-orbit couplings, and spin-valley interactions. While there are several techniques for developing TMD based devices, in this work we propose a unique, precursor free, Chemical Vapor Deposition (CVD) method in which the device in grown in situ with naturally formed contacts. A molybdenum metal pattern, which will form an electrical contact with the TMD, is sputtered on to the substrate prior to the growth. The oxide layer that then naturally forms on the metal surface serves as the precursor for the subsequent growth. In contrast to completely sulfurizing an ultrathin Mo layer, the TMD material grows on, and away from, the thick molybdenum patterns across the Si substrate. Photoluminescence and Raman studies show that the growth can be tuned to produce monolayer and bi-layer Molybdenum Disulfide (MoS2). We also study the self-limiting nature of the growth process and compare it to the growths with the MoO3 precursor. |
Wednesday, March 6, 2019 1:15PM - 1:27PM |
L33.00011: Ab-initio Calculations of Electronic Properties of Orthorhombic Tin Selenide (SnSe). Yuriy Malozovsky, Shaibu Mathias, Lashounda Franklin, Diola Bagayoko We present results from ab-initio, self-consistent density functional theory (DFT) calculations of electronic properties of tin selenide (SnSe) in the orthorhombic B16 crystal structure. We utilized a local density approximation (LDA) potential and the linear combination of atomic orbital (LCAO) formalism. Our calculations minimized the energy down to the ground state, as required by the second DFT theorem. This process ensures the full, physical content of our findings that include electronic energy bands, total and partial densities of states, and electron and hole effective masses. |
Wednesday, March 6, 2019 1:27PM - 1:39PM |
L33.00012: Microscopic polarization and magnetization fields in extended systems Perry Mahon, Rodrigo A. Muniz, John Edward Sipe We introduce microscopic polarization and magnetization fields at each site of an extended system, as well as free charge and current density fields associated with charge movement from site to site, by employing an approach based on a set of orthogonal orbitals at each site. These microscopic fields are defined using a single-particle electron Green function. For an infinite crystal we choose the orbitals to be maximally-localized Wannier functions, and in the longwavelength limit we recover the expected linear response of an insulator, including the zero frequency transverse conductivity. For a topologically trivial insulator we recover the expected expressions for the macroscopic polarization and magnetization in the ground state, and find that the linear response to excitation at arbitrary frequency is described solely by the microscopic polarization and magnetization fields. For very general optical response calculations the microscopic fields automatically satisfy charge conservation, even under basis truncation, and do not suffer from the false divergences at zero frequency that can plague response calculations using other approaches. |
Wednesday, March 6, 2019 1:39PM - 1:51PM |
L33.00013: Carbon nanotube-quantum dot paper for radiation sensitive Electro-mechanical system Sukanta Nandi, Buddha Deka Boruah, Abha Misra Hybrid nanostructures offer unparalleled properties by coupling different functionalities. Surface modification of multiwalled carbon nanotubes (MWCNTs) by in-situ decoration of zinc oxide quantum dots (ZnO QDs) i.e. ZnO QDs@MWCNTs induces highly sensitive opto-electro-mechanical response. Freestanding paper of ZnO QDs@MWCNTs demonstrated an enhancement of ~122% in the response current upon infrared (radiation) illumination as compared to only MWCNT paper. Moreover, the radiation interaction revealed a comparatively quicker response and recovery time of ~42.4% and ~19.4% respectively. Electro-mechanical measurements revealed a ~349% increment in actuation at 3 V bias owing to increase in net polarization enhancement. Radiation induced actuation further revealed a ~111 ± 4% actuation compared to the electro-mechanical actuation. Through this work we demonstrate MWCNT coupled with dielectric QDs paves extraordinary functionalities altogether for the development of smart micro-opto-electro-mechanical systems. |
Wednesday, March 6, 2019 1:51PM - 2:03PM |
L33.00014: WITHDRAWN ABSTRACT
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