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arXiv 2023年

作者： Liang, Xiao Durmusoglu, Emek G. Lunina, Maria Hernandez-Martinez, Pedro Ludwig Valuckas, Vytautas Yan, Fei Lekina, Yulia Sharma, Vijay Kumar Yin, Tingting Ha, Son Tung Shen, Ze Xiang Sun, Handong Kuznetsov, Arseniy Demir, Hilmi Volkan LUMINOUS Center of Excellence for Semiconductor Lighting and Displays The Photonics Institute School of Electrical and Electronic Engineering Nanyang Technological University Singapore639798 Singapore Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Interdisciplinary Graduate Program Nanyang Technological University Singapore637371 Singapore 2 Fusionopolis Way #08-03 Innovis 138634 Singapore UNAM-Institute of Materials Science and Nanotechnology The National Nanotechnology Research Center Department of Electrical and Electronics Engineering Department of Physics Bilkent University Bilkent Ankara06800 Turkey

The strength of electrostatic interactions (EI) between electrons and holes within semiconductor nanocrystals profoundly impact the performance of their optoelectronic systems, and different optoelectronic devices demand distinct EI strength of the active medium. However, achieving a broad range, fine-tuning of the EI strength for specific optoelectronic applications is a daunting challenge, especially in quasi 2-dimensional core-shell semiconductor nanoplatelets (NPLs), as the epitaxial growth of the inorganic shell along the direction of the thickness that solely contributes to the quantum confined effect significantly undermines the strength of the EI. Herein we propose and demonstrate a novel doubly-gradient (DG) core-shell architecture of semiconductor NPLs for on-demand tailoring of the EI strength by controlling the localized exciton concentration via in-plane architectural modulation, demonstrated by a wide tuning of radiative recombination rate and exciton binding energy. Moreover, these exciton-concentration-engineered DG NPLs also exhibit a near-unity quantum yield, remarkable thermal and photo stability, as well as considerably suppressed self-absorption. As proof-of-concept demonstrations, highly efficient color converters and high-performance light-emitting diodes (external quantum efficiency: 16.9%, maximum luminance: 43, 000 cd/m2) have been achieved based on the DG NPLs. This work thus opens up new avenues for developing high-performance colloidal optoelectronic device applications. Copyright © 2023, The Authors. All rights reserved.

关键词： Quantum yield

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Giant Thermomechanical Bandgap engineering in Quasi-two-dimensional Tellurium

arXiv

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arXiv 2023年

作者： Hussain, Naveed Ahmed, Shehzad Tep, Hüseyin U. Ullah, Kaleem Shahzad, Khurram Wu, Hui Shcherbakov, Maxim R. Department of Electrical Engineering and Computer Science University of California Irvine IrvineCA92697 United States State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing100084 China College of Physics and Optoelectronic Engineering Shenzhen University Guangdong518060 China Micro and Nano-Technology Program School of Natural and Applied Sciences Middle East Technical University Ankara06800 Turkey Department of Electrical and Computer Engineering University of Delaware NewarkDE19711 United States Department of Physics Middle East Technical University Ankara06800 Turkey

Mechanical straining-induced bandgap modulation in two-dimensional (2D) materials has been confined to volatile and narrow modulation due to substrate slippage and poor strain transfer. We report the thermomechanical modulation of the inherent bandgap in quasi-2D tellurium nanoflakes (TeNFs) via non-volatile strain induction during hot-press synthesis. We leveraged the coefficient of thermal expansion (CTE) mismatch between TeNFs and growth substrates by maintaining a high-pressure enforced non-slip condition during thermal relaxation (623 to 300K) to achieve the optimal biaxial compressive strain of -4.6 percent in TeNFs/sapphire. This resulted in an enormous bandgap modulation of 2.3 eV, at a rate of up to ~600 meV/%, which is two-fold larger than reported modulation rate. Strained TeNFs display robust band-to-band radiative excitonic blue photoemission with an intrinsic quantum efficiency (IQE) of c.a. 79.9%, making it promising for energy efficient blue LEDs and nanolasers. Computational studies reveal that biaxial compressive strain inhibits exciton-exciton annihilation by evading van-Hove singularities, hence promoting radiative-recombination. Bandgap modulation by such nonvolatile straining is scalable to other 2D semiconductors for on-demand nano(opto)-electronics. Copyright © 2023, The Authors. All rights reserved.

关键词： Energy gap

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Numerical Modeling and Simulation of Dropped Granular Particles on the Curved Surface 11

Numerical Modeling and Simulation of Dropped Granular Partic...

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11th National physics Seminar, SNF 2022

作者： Muliyati, D. Sumardani, D. Mutoharoh, M. Sari, N.L.K. Department of Physics Education Universitas Negeri Jakarta Jl. Rawamangun Muka Jakarta13220 Indonesia Pusat Pengembangan Media Digital Universitas Negeri Jakarta Jl. Rawamangun Muka Jakarta13220 Indonesia Teachers College National Chiayi University Chiayi City60004 Taiwan Industry Engineering Study Program Universitas Krisnadwipayana Jatiwaringin Bekasi13077 Indonesia Department of Physics Fakultas Teknik Dan Sains Universitas Nasional Jl. Sawo Manila Pejaten Ps. Minggu Jakarta12520 Indonesia

This study aims to present an approach for analyzing the performance of granular cosmetic adhesion by a numerical simulation using the uFlex particle. To ensure the viability of a numerical simulation, the effect of the process parameters on the dropping granular performance such as curve type, surface moisture level, and curve angle was evaluated. Results suggest that the humidity and curvature angle have significant effects on the density of cosmetic particles on the surface, while the other parameter have relatively small effects. Moreover, the effect of each parameter on the granular adhesion at the surface has been explained by utilizing the particle analysis after the collision. The simulation result shows the adhesion of granular particles with a curved surface leads to better performance under moist surfaces with a convex shape at the angle of 0 degrees. However, on all curvatures, worse adhesion performance under dry surfaces with convex shape. © Published under licence by IOP Publishing Ltd.

关键词： Adhesion

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Non-Empirical Models for Assessing the Thermal Properties of Nonlinear Polyatomic Molecules

SSRN

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SSRN 2025年

作者： Eyube, Edwin Samson Yabwa, D. Onate, C.A. Makama, E.K. Tahir, A.M. Omugbe, E. Makasson, C.R. Umar, U. Department of Physics Faculty of Physical Sciences Modibbo Adama University P.M.B. 2076 Adamawa State Yola Nigeria Department of Physics Faculty of Science Taraba State University P.M.B. 1176 Taraba State Jalingo Nigeria Physics Program College of Agriculture Engineering and Science Bowen University Osun State Iwo Nigeria Department of Physics Faculty of Natural Sciences University of Jos P.M.B. 2084 Plateau State Jos Nigeria Department of Science Laboratory Technology School of Science and Technology Adamawa State Polytechnic P.M.B. 2146 Adamawa State Yola Nigeria Department of Physics University of Agriculture and Environmental Sciences Umuagwo P.M.B. 1038 Imo State Nigeria Department of Physics Modibbo Adama University Secondary School P.M.B. 2076 Adamawa State Yola Nigeria

The current study explores computational models developed using the improved Scarf potential and harmonic oscillator to simulate vibrational modes in nonlinear polyatomic systems. These models are derived from the partition functions of the system and are designed to predict molar Gibbs free energy, entropy, enthalpy, and heat capacity. The models are applied to nonlinear polyatomic molecules, including aluminum chloride (AlCl2), boron difluoride (BF2), and sulfur dioxide (SO2). For Gibbs free energy and entropy, the equations yield a mean percentage relative error (MPRE) of no more than 0.09% compared to NIST data. Furthermore, using the heat capacity expression, MPRE values of 0.968%, 1.035%, and 2.764% are obtained for AlCl2, BF2, and SO2, respectively. These findings are in good agreement with results from existing literature on nonlinear molecules © 2025, The Authors. All rights reserved.

关键词： Free energy

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On the approximability of random-hypergraph MAX-3-XORSAT problems with quantum algorithms

arXiv

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arXiv 2023年

作者： Kapit, Eliot Barton, Brandon A. Feeney, Sean Grattan, George Patnaik, Pratik Sagal, Jacob Carr, Lincoln D. Oganesyan, Vadim Department of Physics Colorado School of Mines 1523 Illinois St GoldenCO80401 United States Department of Applied Mathematics and Statistics Colorado School of Mines 1500 Illinois St GoldenCO80401 United States Quantum Engineering Program Colorado School of Mines 1523 Illinois St GoldenCO80401 United States Department of Physics and Astronomy College of Staten Island CUNY Staten IslandNY10314 United States Physics Program and Initiative for the Theoretical Sciences The Graduate Center CUNY New YorkNY10016 United States Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New YorkNY10010 United States

A canonical feature of the constraint satisfaction problems in NP is approximation hardness, where in the worst case, finding sufficient-quality approximate solutions is exponentially hard for all known methods. Fundamentally, the lack of any guided local minimum escape method ensures both exact and approximate classical approximation hardness, but the equivalent mechanism(s) for quantum algorithms are poorly understood. For algorithms based on Hamiltonian time evolution, we explore this question through the prototypically hard MAX-3-XORSAT problem class. We conclude that the mechanisms for quantum exact and approximation hardness are fundamentally distinct. We review known results from the literature, and identify mechanisms that make conventional quantum methods (such as Adiabatic Quantum Computing) weak approximation algorithms in the worst case. We construct a family of "spectrally filtered" quantum algorithms that escape these issues, and develop analytical theories for their performance. We show that, for random hypergraphs in the approximation-hard regime, if we define the energy to be E = Nunsat - Nsat, spectrally filtered quantum optimization will return states with E ≤ qmEGS (where EGS is the ground state energy) in sub-quadratic time, where conservatively, qm 0.59. This is in contrast to qm → 0 for the hardest instances with classical searches. We test all of these claims with extensive numerical simulations. We do not claim that this approximation guarantee holds for all possible hypergraphs, though our algorithm’s mechanism can likely generalize widely. These results suggest that quantum computers are more powerful for approximate optimization than had been previously assumed. © 2023, CC BY.

关键词： Constraint satisfaction problems

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Inter-Modular Synchronization in a TOF-PET System Using the Natural LYSO Background Radioactivity

Inter-Modular Synchronization in a TOF-PET System Using the ...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Qian Dong Salar Sajedi Craig S. Levin Departments of Electrical Engineering and Radiology Stanford University Stanford CA USA Departments of Radiology Stanford University Stanford CA USA Department of Radiology Electrical Engineering Bioengineering and Physics Stanford University and Molecular Imaging Program at Stanford (MIPS) Stanford CA USA

Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) is a promising platform for clinical and research with applications in oncology, neurology, cardiology, and inflammatory diseases. One challenge for simultaneous PET/MRI is the mutual electromagnetic interference between the two imaging modalities. MR-compatibility is required for any system integrating with an MR scanner. It is difficult to achieve both time-of-flight (TOF) capability and MR compatibility using the standard inter-modular synchronization method that uses synchronization signals based on either optical fibers or electrical cables. In this paper, we propose a new method to achieve inter-modular synchronization for PET systems without additional electrical cables or optical fibers by using the natural background radiation present in lutetium-yttrium oxyorthosilicate (LYSO) scintillator crystals. We investigated the feasibility of the approach with two full detector modules comprising 1536 one-to-one coupled 3x3x20mm 3 LYSO crystal-silicon photomultipliers (SiPM) channels. Using the natural LYSO background radiation for synchronization resulted in a CTR of 274.6ps FWHM with a peak location at -13.8ps, compared to the re-calibrated (reference) results with a CTR of 271.1ps FWHM with a peak location at -10.3ps.

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Investigation of Faraday Cage Materials with Low Eddy Current and High RF Shielding Performance for PET/MRI Applications

Investigation of Faraday Cage Materials with Low Eddy Curren...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Qian Dong Zander Adams Ronald D. Watkins Craig S. Levin Departments of Electrical Engineering and Radiology Stanford University Stanford CA USA Departments of Radiology Stanford University Stanford CA USA Department of Radiology Electrical Engineering Bioengineering and Physics Stanford University and Molecular Imaging Program at Stanford (MIPS) Stanford CA USA

After the successful fusion of positron emission tomography (PET) and computed tomography (CT), the attention turned to integrating PET and magnetic resonance imaging (MRI). The most significant challenges in integrating PET and MR systems arise from the potential for mutual interference between the systems. The main magnetic field B0 can be disturbed by trace amounts of magnetic materials, leading to MR susceptibility artifacts. The high-power RF field B1 may induce currents in or even damage PET electronics inside the MR system without protection. The MR system gradient fields can induce a large eddy current in conductive loops in PET detectors, causing further image distortions. The purpose of this work is to investigate shielding efficiency, gradient-induced eddy current, and MR susceptibility performance of six different shielding materials: copper plate, copper tape, carbon fiber fabric, stainless steel (304) mesh, phosphor bronze mesh, and conductive coating. The RF noise results show a lower bound shielding efficiency (SE) of 43.3dB for copper plate, copper tape, phosphor bronze mesh, and conductive coating and measured SEs 42.9dB and 42.5dB for stainless steel mesh and carbon fiber fabric. Cooper plate and copper tape generated the largest ghosting artifacts from eddy currents, increasing percent signal ghosting (PSG) 106%/12.3%/111.6%, and 20.8%/7%/24.3% in the axial/sagittal/coronal plane, respectively. For MR susceptibility evaluation, stainless steel mesh had the highest pixel value difference (7.4 ± 3.6Hz) compared with the reference. Copper tape and conductive coating also showed a slightly larger difference, 3.7 ± 2.3Hz and 3.9 ± 1.1Hz, respectively. Although conductive coating does not have the lowest susceptibility, owing to its easy manufacturing process and consistent performance, we choose it as the Faraday cage material in our MR-compatible PET insert.

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Cascaded forward Brillouin lasing in a chalcogenide whispering gallery mode microresonator

arXiv

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arXiv 2022年

作者： Shanavas, Thariq Grayson, Michael Xu, Bo Zohrabi, Mo Park, Wounjhang Gopinath, Juliet T. Department of Physics University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Materials Science Engineering Program University of Colorado BoulderCO80309 United States

We report the first observation of cascaded forward stimulated Brillouin scattering in a microresonator platform. We have demonstrated 25 orders of intramodal Stokes beams separated by a Brillouin shift of 34.5 MHz at a sub-milliwatt threshold at 1550 nm. An As2S3 microsphere of diameter 125 µm with quality factor 1×106 was used for this demonstration. Theoretical modeling is used to support our experimental observations of Brillouin shift and threshold power. We expect our work will advance the field of forward stimulated Brillouin scattering in integrated photonics with applications in gas sensing and photonic radio frequency sources. Copyright © 2022, The Authors. All rights reserved.

关键词： Microresonators

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Quantum oscillation studies of the nodal line semimetal Ni3In2S2-xSex

arXiv

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arXiv 2025年

作者： Sharma, M.M. Chhetri, Santosh Karki Acharya, Gokul Graf, David Upreti, Dinesh Dahal, Sagar Un Nabi, Md Rafique Rahman, Sumaya Sakon, Josh Churchill, Hugh O.H. Hu, Jin Department of Physics University of Arkansas FayettevilleAR72701 United States National High Magnetic Field Lab TallahasseeFL32310 United States MonArk NSF Quantum Foundry University of Arkansas FayettevilleAR72701 United States Material Science and Engineering Program Institute for Nanoscience and Engineering University of Arkansas FayettevilleAR72701 United States Department of Chemistry & Biochemistry University of Arkansas FayettevilleAR72701 United States

Ternary shandite compounds with the general formula T3M2X2 (T = Ni, Co, Rh or Pd;M = Sn, In, or Pb;and X = S or Se) have emerged as a large pool of topological semimetals. This family of compounds hosts different topological phases for various combinations of T, M and X. This paper reports the observation of quantum oscillations under the high magnetic fields in Ni3In2S2-xSex single crystals. Angular dependence of oscillation frequency suggests an evolution of the Fermi surface from three-dimensional to two-dimensional on Se substitution for S in Ni3In2S2. The effective mass obtained for each composition by fitting the oscillation amplitude with the Lifshitz-Kosevich formula, shows no significant change, suggesting that the topological phase might be relatively robust against enhanced SOC upon Se doping in Ni3In2S2 Copyright © 2025, The Authors. All rights reserved.

关键词： Single crystals

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Initial System Performance Evaluation of a Second-Generation RF-Penetrable Brain TOF-PET Insert for Simultaneous PET/MRI

Initial System Performance Evaluation of a Second-Generation...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Qian Dong Chen-Ming Chang Andrew Groll Ilaria Sacco Ronald D. Watkins Derek Innes Zander Adams Craig S. Levin Departments of Electrical Engineering and Radiology Stanford University Stanford CA USA Departments of Radiology Stanford University Stanford CA USA Department of Radiology Electrical Engineering Bioengineering and Physics Stanford University Molecular Imaging Program at Stanford (MIPS) Stanford CA USA

Simultaneous positron emission tomography / magnetic resonance imaging (PET/MRI) has unique advantages in providing complementary, concurrent information about anatomic, functional, and molecular changes in diseases. We are developing an MR-compatible RF-penetrable brain time-of-flight (TOF)-PET insert with a smaller scintillation crystal size and smaller PET ring diameter compared to clinical whole-body PET scanners, which leads to higher spatial resolution and sensitivity. We reported PET performance and MR-compatibility of our MR-compatible detector modules before. This paper reports the initial PET system performance of our second-generation RF-penetrable PET insert with half of the system (8 out of 16 detector modules) assembled. The excellent global photopeak energy resolution and global CTR, 230.5 ± 0.2ps FWHM and 11.29 ± 0.01% FWHM, are preserved as we scale up the system. The coincidence count rate is 92.7 ± 0.1 kcps and the average temperature of all ASIC chips on 8 detector modules is 24.4 ± 0.2 oC over a one-hour point source experiment. The system performance during the one hour experiment is stable. For the resolution phantom study, we can resolve all 3.2mm rods and part of 2.8mm rods without applying normalization, TOF, scatter, attenuation, and random corrections. The image quality will be significantly improved after we assemble the remaining detector modules and implement all image corrections. We will report a resolution phantom study with the full 16 detector modules assembled and all image corrections implemented and MR compatibility evaluation at the conference.

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