Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X28: AMO phenomena in the solid stateLive
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Sponsoring Units: DAMOP Chair: Srivatsan Chakram, Rutgers |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X28.00001: Coupling Among Dark Excitons, Bright Excitons, and Photons in Semiconducting Carbon Nanotube Microcavity Polaritons Abitha Dhavamani, Louis Haeberle, Jialiang Wang, Stephane Kena-Cohen, Michael Arnold Semiconducting single-walled carbon nanotubes (SWCNTs) are an exquisite candidate for realizing stable room-temperature exciton-polaritons. They possess a combination of bright and dark excitonic states, with the latter sometimes “brightened” by vibrational transitions through external oscillation energies (e.g., a phonon). Yet, manipulating such dark excitonic states is tedious, given their weak coupling strengths. We show here that strong light-matter interaction allows for hybridization of bright and dark excitonic states mediated by a common cavity photon and exciton-phonon coupling. This coupling creates new eigenstates at tunable wavelengths that were formally non-emissive, in addition to the conventional polaritonic states that arise from typical excitonic transitions. This unique interaction is demonstrated in an optical cavity containing high density (>40 wt%) (6,5) SWCNTs. The high quality-factor of the cavity fabricated by a custom lamination approach have enabled us to accomplish high coupling strengths of >90meV for the dark exciton-phonon-photon coupled states. The large SWCNT density and the lamination technique also result in ultra-strong coupling between bright exciton and photon states, with a Rabi splitting of ∼450meV and narrow band emission (FWHM of 30 meV). |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X28.00002: First Principles Study of the Electronic Structure and Optoelectronic Properties of Ultra-Wide Bandgap Semiconductor Compound NaYO2 Nisar Muhammad, Ding Zejun, H.M Li Ultra-wide bandgap semiconductor materials have attained enormous attention from scientific community owing to their great potential in technological applications. The underestimated bandgap calculated from the standard density-functional theory (DFT) in the generalized gradient approximation (GGA), cannot predict the material properties accurately’ close to experiment. Herein, going beyond the DFT, we employ the more advance and accurate screened-hybrid functional DFT approach to evaluate the electronic and optical properties for monoclinic and trigonal phase of NaYO2. Our calculated bandgap value for monoclinic phase is 5.4 eV with HSE06 functional match experimental value and depicts that previously theoretical value was underestimated. Optical properties with HSE06 functional show reduction in intensity along with significant blue shift from PBE-GGA. We validate the dynamic stability of both phases from negation of no negative frequency in phonon spectrum. Our calculations confirm NaYO2 as large direct band gap that could be promising candidate for solar blind detector and environment technology. |
Friday, March 19, 2021 8:24AM - 8:36AM Live |
X28.00003: Imperfect electron-hole recollisions in high-harmonic generation in monolayer and bulk solids Lun Yue, Mette B. Gaarde High-harmonic generation (HHG) in solids has attracted increased attention in recent years due to its exciting prospects for the engineering of new light sources and ultrafast spectroscopy methods. We present theoretical results on the process of imperfect recollisions in solid-state HHG, wherein an electron and a hole can recombine even when they are spatially separated. We consider two general types of materials: a monolayer material represented by hexagonal boron nitride (hBN) and a bulk solid represented by ZnO. In hBN, imperfect recollisions can be induced by linearly-polarized laser pulses, while elliptically-polarized pulses are required for ZnO. We discuss the general mechanisms and conditions for the imperfect recollisions. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X28.00004: In-situ probing of photoinduced charge transfer dynamics in nanoplasmonic light-harvesting systems using time-resolved ambient pressure x-ray photoelectron spectroscopy Matthew Fraund, Mario Borgwardt, Felix Brausse, Friedrich Roth, Monika Blum, Oliver Gessner Photocatalytic production of hydrogen fuel via photoelectrochemical (PEC) water splitting is a clean and renewable process that is both less efficient and economically viable than non-renewable methods. To improve solar light harvesting and charge separation in the photocatalyst, plasmonic metal nanoparticles (NPs) are used to sensitize wide-bandgap semiconductors due to their chemical stability and strong absorption at visible wavelengths. Here, a model system of 20 nm gold NPs atop a layer of TiO2 is studied with picosecond time-resolved ambient pressure x-ray photoelectron spectroscopy (TRAPXPS), which allows monitoring of charge dynamics on the electron donor and acceptor sites separately. Measurements are performed under high vacuum conditions and with ~9 Pa of water vapor. In vacuum, a charge injection efficiency of ~2 electrons per NP (~0.1% photon-to-charge efficiency) is observed, followed by recombination over two timescales: 60 ps and ~1 ns.1 After introduction of water vapor, charges remain separated for longer, and relaxation is now described by 3 timescales: ~0.9 ns, ~11 ns, and ~150 ns. Possible physical interpretations, including the role of water dipoles in extending recombination, will be discussed. |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X28.00005: Measurement of the Thulium Ion Spin Hamiltonian Within a Yttrium Gallium Garnet Host Crystal Jacob Davidson, Phillip Woodburn, Aaron Marsh, Kyle Olson, Adam Olivera, Mohsen Falamarzi Askarani, Antariksha Das, Wolfgang Tittel, Rufus Cone, Charles W Thiel We characterize the magnetic effects present for thulium ions in a Y3Ga5O12 (Tm:YGG) lattice. In this work we measure hyperfine tensors for the ground, 3H6, and excited, 3H4, states using a combination of spectral hole burning and optically detected nuclear magnetic resonance (ODNMR). From these techniques we measure and fit the orientation dependence of the Tm3+ ion's spin-Hamiltonian by rotating the sample through a series of angles with an external magnetic field. Independent measurements of the level splittings and optical transition shifts at a fixed external field orientation show good agreement with the measured tensor parameters. Using this measured spin-Hamiltonian we propose a set of orientations based on the ZEFOZ technique, [1], to improve optical coherence, and spin level in-homogeneous broadening, both of which are desirable for light-matter interaction and quantum information applications in this material. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X28.00006: Per pixel lock in detection based dynamic widefield magnetometry using quantum defects in diamond Madhur Parashar, Dasika Shishir, Alok Gokhale, Anuj Bathla, Sharba Bandyopadhyay, Kasturi Saha Ultrasensitive microscale widefield magnetometry, based on magnetic resonance of nitrogen vacancy defects (NV) in diamond, have been applied to varied applications, for example imaging magnetic nanoparticles in living cells. However, in probing slow varying magnetic field these magnetometers are limited by trade-offs in per-pixel magnetic sensitivity and bandwidth of the sensor, limiting applications to imaging at millisecond timescales. For slow varying magnetic fields regime, lock-in detection of optically detected magnetic resonance spectrum (ODMR) has allowed pico-nanotesla magnetic field sensitivity maintaining DC to few Kilohertz bandwidth, however focusing all NV emitted light onto a single photodiode. In this work, we extend the lock-in measurements to a widefield area by using a lock in camera which can perform simultaneous per pixel demodulation up to few hundred kilohertz. We measure lock-in ODMR spectrum over hundreds of pixels, reconstruct static magnetic field and perform dynamic-widefield-magnetic field tracking. In addition we also obtain a single photodiode sensitivity of 54nT/sqrt(Hz) with magnetic field tracking at 500ms temporal resolution. We discuss further improvements in sensitivity that are required to enable millisecond scale magnetic imaging. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X28.00007: Quantum friction in the Hydrodynamic Model KUNMIN WU, Thomas L Schmidt, Maria Belen FARIAS We study the phenomenon of quantum friction in a system consisting of a polarizable atom moving at a constant speed parallel to a metallic plate. The metal is described using a charged hydrodynamic model for the electrons. This model featuring long-range interactions is appropriate for a clean metal in a temperature range where scattering due to Coulomb interactions dominates over the scattering of electron by impurities. We find that a quantum friction force between the atom and the metal surface exists even in the absence of intrinsic damping in the metal, but that it only starts once the velocity of the atom exceeds the effective speed of sound in the metal. We argue that this condition can be fulfilled most easily in metals with nearly empty or nearly filled bands. We make quantitative predictions for the friction force to the second and fourth order in the atomic polarizability, and show that the threshold behavior persists to all orders of the perturbation theory. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X28.00008: Tunable toroidal excitation in a reconfigurable terahertz metamaterial Chunxu Chen, Kelson Kaj, Yuwei Huang, Xiaoguang Zhao, Richard Averitt, Xin Zhang Compared with the traditional electric and magnetic multipolar excitation, the existence of a dynamic toroidal moment has received increasing interest in recent years due to its novel electromagnetic response. In this work, we present unique reconfigurable terahertz metamaterials where artificial toroidal metamolecules and traditional MEMS bi-material cantilever structures are integrated within the same unit cell. Through modification of the bending angle through thermal stimulus, the intensity of the toroidal moment increases by approximately 5 orders of magnitude. The toroidal excitation is measured using terahertz time-domain spectroscopy and confirmed numerically with a multipole decomposition method. Our results demonstrate the use of bi-material cantilevers to realize a tunable toroidal moment. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X28.00009: Time-Resolved Optical Spectroscopy of Electrically Gated Single Quantum Emitters Melanie Dieterlen, Erin Sheridan, Patrick R Irvin, Jeremy Levy, Kitae Eom, Chang-Beom Eom Quantum emitters such as nanocrystalline quantum dots or point defects in solid state materials have the potential to produce single photons on demand. We have developed a novel optical spectrometer capable of probing the transient response of single quantum emitters with dimensions ~10 nm or less over a wide range of frequencies in THz and NIR [1]. The experiments take advantage of strong nonlinearities in SrTiO3 and the ability to “write” conductive nanowires at the LaAlO3/SrTiO3 interface, with ~10 nm gaps co-located with a single quantum emitter. We will probe a variety of single quantum emitters individually under the influence of large electric fields and look for Stark shifts in absorption or emission in the quantum dots, and gate-controlled lifetime/emission effects. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X28.00010: Controlling the hot carrier tunneling direction in nanogaps Mahdiyeh Abbasi, Yunxuan Zhu, Douglas Natelson Plasmonic structures can be tuned to absorb light resonantly at a particular wavelength. When the width of the nanowire in the middle of a gold bowtie structure is resonant to a wavelength, we observed increased thermal absorption at the nanowire. The Seebeck coefficient of a metal depends on the energy-dependent electrical conductivity, which in turn depends on the energy-dependent electron mean free path. In a single metal bowtie structure, the Seebeck coefficient changes as a function of the width of the device. Combined with a plasmonically resonant width for the nanowire, this leads to an open-circuit photovoltage optimized for a wavelength when the device is illuminated with a laser. Forming a nanometer-scale gap in the gold nanowire can increase the photovoltage signal by up to 1000 times due to hot electron tunneling. Our previous study showed that the polarity of the photothermoelectric signal in the gap in pure Au wires is sensitive to atomic-scale details of the junction. We propose a structure with a nanogap between gold and palladium nanowires such that plasmon-generated hot electrons in the Au have a preferred direction to tunnel. This structure enables the control of hot carrier tunneling direction. We will share preliminary results. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X28.00011: Enhancement of Electric and Magnetic Emission in Langmuir Blodgett Films and Sandwich Structures with Eu3+ Ions JOHN MUNGA, Tejaswini Ronur Praful, David Keene, MD Afzalur Rab, Nelly Jerop, Festus Bett, Maxim Durach, Natalia Noginova Plasmonic structures provide possibilities to control and enhance spontaneous emission, including emission, at weak magnetic transitions, which is of interest for various applications. However, quenching in metal via near field excitations may present significant problems. In our work, we compare systems with dense and dilute arrangement of emitters, and experimentally study efficiency of emission and radiation patterns of electric and magnetic emitters in close vicinity of plasmonic films, gratings and inside sandwich-like structures. We show that monolayer or multilayer Langmuir Blodgett films of closely packed EuTTA molecules deposited on metal demonstrate reduced quenching and significantly enhanced excitation of surface plasmon polaritons in comparison with films where Eu ions are diluted. The results are discussed taking into account modifications of near field effects. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X28.00012: Graphene Sandwich Stable Perovskite Quantum-Dots Light Emissive Ultrasensitive and Ultrafast Broadband Vertical Phototransistors KRISHNA PRASAD BERA The dual-functional devices, which can simultaneously detect light and emit light, have a tremendous appeal for multiple applications, including display, sensors, defense, and high-speed optical communication. Despite the tremendous efforts of scientists, the progress of integration of phototransistor, where the built-in electric field separates the photogenerated excitons, and light-emitting diode (LED), where the radiative recombination can be enhanced by band offset, into a single device remains a challenge. Combining the superior properties of perovskite quantum dots (PQDs) and graphene, here we report a light-emissive, ultrasensitive, ultrafast, and broadband vertical phototransistor, which can simultaneously act as an efficient photodetector and light emitter within a single device. The estimated value of external quantum efficiency (EQE) of the vertical phototransistor is ~ 1.2×1010% and photoresponsivity > 109 AW-1 with response time of < 50 µs, which exceed all the presently reported vertical phototransistor devices. We also demonstrate that the modulation of the Dirac point of graphene efficiently tunes both amplitude and polarity of the photocurrent. The device exhibits a green emission having a quantum efficiency of 5.6%. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X28.00013: Photoresponse of a Dirac-Weyl interface composed of graphene and WTe2 Farima Farahmand, Jacky Wan, Jedediah Kistner-Morris, Nathaniel Monroe Gabor Although Graphene and WTe2 are both atomically thin semimetals whose density of states diminishes at the charge neutrality point, each exhibit highly distinct band topologies in their low energy electronic structure. While graphene hosts Dirac-like excitations with highly symmetric electron and hole bands, WTe2 has been shown to be a type II Weyl semimetal with compensated electron-hole pockets. Photoexcitation combined with electronic magneto-transport provides a deep understanding of the dynamics that govern electrical and optical conductivities and give us an opportunity to explore the consequences of unusual band topologies at a Dirac-Weyl interface. Here, we use scanning photocurrent microscopy to study the local photoresponse at a van der Waals heterojunction of WTe2 and Graphene. We examine the semimetal-semimetal interface response as a function of interlayer voltage, local gate voltage, laser power, wavelength, and magnetic field, finding highly sensitive photoresponsivity attributed to a photo-thermoelectric effect. Our measurements establish the groundwork for low temperature studies into the origins of this unusual photoresponse and give important insights into the design and development of unique magneto-optoelectronic sensors based on WTe2. |
Friday, March 19, 2021 10:36AM - 10:48AM Live |
X28.00014: Tuning resonance energy transfer with magneto-optical properties of graphene Patrícia Abrantes, Guilherme Bastos, Daniela Szilard, Carlos Farina, Felipe Rosa Resonance energy transfer (RET) is an important mechanism throught which an excited quantum emitter may transfer its energy to a neighboring one in the ground state. Amid the several situations where RET plays a relevant role, a remarkable one is the light harvesting process in plants, in which chlorophyll molecules excite themselves by absorbing light and efficiently transfer this excitation energy to their neighboring molecules. An efficient energy transfer allows a variety of applications, such as photovoltaics, luminescence, sensing, and many others. Due to this numerous applications, controlled modification of the RET rate has become a topic of great interest. In this work we take advantage of graphene's magneto-optical response and investigate the RET between two emitters placed in the vicinity of a suspended graphene monolayer in vacuum, submitted to a perpendicular external magnetic field. We show that the RET rate may change dramatically with respect to the result in free space even for small modulations of the magnetic field and this effect may be obtained even for somewhat modest values of the field. |
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