Article
Chemistry, Multidisciplinary
Majed Alshammari, Alaa A. Al-Jobory, Turki Alotaibi, Colin J. Lambert, Ali Ismael
Summary: Through research, it has been discovered that single-molecule junctions formed from different materials can exhibit bi-thermal behavior, depending on the orientation of the molecule within the junction. This finding contributes to improving the efficiency of molecular-scale thermoelectric energy generators.
NANOSCALE ADVANCES
(2022)
Article
Nanoscience & Nanotechnology
Henrikh M. Baghramyan, Cristian Ciraci
Summary: This article discusses the role of plasmonic nanoparticles in enhancing fluorescent emission. They locally amplify the electromagnetic fields and provide a high local density of states, leading to an increase in the excitation rate and spontaneous emission of the emitter. However, when the emitter is placed near a single metal nanoparticle, the number of nonradiative states increases, resulting in fluorescence quenching. Taking into account quantum effects, such as electron tunneling, is important to correctly describe the emission effects in plasmonic systems at the nanoscale.
Article
Nanoscience & Nanotechnology
Angela L. Paoletta, E-Dean Fung, Latha Venkataraman
Summary: In this study, Au tunnel junctions are used to simultaneously probe electroluminescence and conductance. It is found that plasmonic enhancement increases with decreasing gap size for junctions biased between 1.4 and 1.8 V, while above 1.9 V, plasmonic enhancement decreases due to quenching caused by tunneling, which is consistent with trends observed for high energy plasmons in scattering experiments.
Article
Physics, Multidisciplinary
Hiromi Ebisu, Noam Schiller, Yuval Oreg
Summary: In this work, the heat flow between two 1 + 1D chiral gapless systems connected by a point contact is theoretically studied. It is found that the ratio between fluctuations of the heat current and the heat current itself is proportional to the scaling dimension. Two different approaches, scattering theory and conformal field theory, are adopted to calculate this ratio and their results agree. The findings are useful for probing both fractional charge excitations in fractional quantum Hall states and neutral ones.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Dukhyung Lee, Dohee Lee, Hyeong Seok Yun, Dai-Sik Kim
Summary: Nanogap slits on a flexible substrate can be used to adjust cavity width by bending the substrate, affecting optical properties with angstrom-scale width control potential. The low displacement ratio comparable to a mechanically controllable break junction highlights the great potential of nanogap slit structures on a flexible substrate, particularly in quantum plasmonics.
Article
Physics, Condensed Matter
Er'el Granot, Gilad Zangwill
Summary: Resonant tunneling can lead to complex current structures when the resonant energy varies in time. While these variations typically increase the current, there is a specific condition where the current is significantly suppressed. This condition is described by the equation 1/2 ∫(t1)(t1) |Omega-Omega R(t')| dt' = pi (n -1/4), and in this paper, a full derivation of this expression is presented using the Quasi-Bound Super State method.
PHYSICA B-CONDENSED MATTER
(2023)
Article
Materials Science, Multidisciplinary
Lin Huang, Yu-Jia Zeng, Dan Wu, Nan-Nan Luo, Ye-Xin Feng, Zhi-Qiang Fan, Li-Ming Tang, Ke-Qiu Chen
Summary: High tunneling magnetoresistance (TMR) can be achieved in molecular junctions based on Co-Salophene symmetric/asymmetric dimers, with nearly 100% spin-injection efficiency (SIE) in parallel spin configuration. The TMR properties are closely related to molecular symmetry, reaching up to 4600% and 2200% for symmetric and asymmetric molecular junctions, respectively.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Chemistry, Multidisciplinary
Douglas Natelson, Yunxuan Zhu, Longji Cui, Mahdiyeh Abbasi
Summary: This study investigates different light emission mechanisms in atomic-sized plasmonic tunnel junctions and demonstrates that the dominant emission mechanism is determined by the combination of tunneling rate, hot carrier relaxation time scales, and junction plasmonic properties.
Article
Physics, Multidisciplinary
Shunji Yamamoto, Hiroshi Imada, Yousoo Kim
Summary: A nanoscopic understanding of spin-current dynamics is crucial for controlling spin transport in materials. However, gaining access to spin-current dynamics at an atomic scale is challenging. Therefore, the development of spin-polarized scanning tunneling luminescence spectroscopy (SP STLS) allows for visualizing the spin relaxation strength depending on spin injection positions. The atomically resolved SP STLS mapping of gallium arsenide reveals a stronger spin relaxation in gallium atomic rows, paving the way for visualizing spin current with single-atom precision.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Samuel L. Rudge, Yaling Ke, Michael Thoss
Summary: This article introduces an approach to calculating current-induced forces in charge transport through nanosystems. By starting from the fully quantum mechanical hierarchical equations of motion formalism, a classical Langevin equation of motion for the vibrational dynamics influenced by current-induced forces is derived through a timescale separation between electronic and vibrational degrees of freedom, such as electronic friction. The numerical exactness of the hierarchical equations of motion approach allows for the investigation of transport scenarios with strong intrasystem and system-environment interactions. As a demonstration, the electronic friction of three example systems is calculated and analyzed: a single electronic level coupled to one classical vibrational mode, an Anderson impurity model coupled to one classical vibrational mode, and a single electronic level coupled to both a classical and quantum vibrational mode.
Article
Chemistry, Multidisciplinary
Wonhee Ko, Sang Yong Song, Jiaqiang Yan, Jose L. Lado, Petro Maksymovych
Summary: This study introduces the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry in low-dimensional unconventional superconductors. By studying the paradigmatic FeSe superconductor, we provide direct evidence of sign-changing order parameter, reveal the existence of two superconducting gaps, and confirm the local suppression of superconductivity along the nematic twin boundary. These findings enable new atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.
Article
Multidisciplinary Sciences
Lukas A. Jakob, William M. Deacon, Yuan Zhang, Bart de Nijs, Elena Pavlenko, Shu Hu, Cloudy Carnegie, Tomas Neuman, Ruben Esteban, Javier Aizpurua, Jeremy J. Baumberg
Summary: Plasmonic nano- and pico-cavities can enhance optomechanical coupling, leading to the softening of molecular bonds. The observed non-linear behavior in the Raman spectra is consistent with theoretical simulations and experimental results.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Cong He, Keisuke Masuda, Jieyuan Song, Thomas Scheike, Zhenchao Wen, Yoshio Miura, Tadakatsu Ohkubo, Kazuhiro Hono, Seiji Mitani, Hiroaki Sukegawa
Summary: This study systematically investigates the nano-crystal domain structures formed in MgO barrier and their effects on tunnel magnetoresistance (TMR) in epitaxial fcc-Co90Fe10 (CoFe)(111)/MgO(111)/CoFe(111) magnetic tunnel junctions (MTJs) using both experimental and first-principles methods. The results reveal the unique formation of nano-crystal domains in the (111)-textured MgO layer and identify three different orientation relationships (ORs) between CoFe and MgO. It is found that one of the ORs has a small contribution to the transport, which explains the discrepancy between experimental and theoretical TMR ratios.
Article
Computer Science, Information Systems
Seyed-Sajad Ahmadpour, Arash Heidari, Nima Jafari Navimpour, Mohammad-Ali Asadi, Senay Yalcin
Summary: With the development of technologies like Internet of Things (IoT) devices, power consumption has become a significant concern. Atomic silicon quantum dot (ASiQD) is an impressive technology for low-power processing circuits, crucial for efficient transmission and power management in micro IoT devices. Multipliers, essential computational circuits in digital circuits, need to be designed with low occupied area and low energy consumption for micro IoT circuits. This article introduces a low-power atomic silicon-based multiplier circuit to effectively manage power in micro IoT. A $4\times 4$ -bit multiplier array with low power consumption and size is presented based on this design, and the circuit is validated using the SiQAD simulation tool. The proposed ASiQD-based circuit significantly reduces energy consumption and area usage compared to recent designs in micro IoT.
IEEE INTERNET OF THINGS JOURNAL
(2023)
Article
Quantum Science & Technology
Qihui Liu, Fei Xie, Xiao Peng, Yuqiang Hu, Nan Wang, Yonggui Zhang, Yang Wang, Lingyun Li, Hao Chen, Jiangong Cheng, Zhenyu Wu
Summary: This study demonstrates an integrated diamond sensor that achieves high sensitivity magnetic field detection through microfabrication processes. By combining it with a magnetic yoke, high-precision direct current sensing is achieved. Temperature drift is effectively suppressed using dual spin resonance modulation.
ADVANCED QUANTUM TECHNOLOGIES
(2023)
Article
Physics, Fluids & Plasmas
De-Qi Wen, Peng Zhang, Janez Krek, Fu Yangyang, John P. Verboncoeur
Summary: In this work, the generation and evolution of higher harmonic (HH) electric fields in multipactor-coexisting plasma breakdown are comprehensively investigated using theoretical modeling and PIC simulations. The study reveals that the fundamental mechanism of HHs generation is stream-plasma instability, and increasing gas pressure significantly reduces the HH oscillations. The parameter space for HH appearance and the effect of driving frequency on HHs are also explored.
PLASMA SOURCES SCIENCE & TECHNOLOGY
(2022)
Article
Physics, Applied
Sneha Banerjee, Peng Zhang
Summary: Terahertz scanning tunneling microscopy enables high-resolution spatiotemporal imaging. This study investigates the rectification of electrons in THz-STM junctions and provides a framework for characterizing and controlling THz-induced currents and probing techniques at the nanometer scale over subpicosecond time periods.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
De-Qi Wen, Asif Iqbal, Peng Zhang, John P. P. Verboncoeur
Summary: In this study, the special features of dielectric multipactor susceptibility under a Gaussian-type waveform are reported. The simulations show that the susceptibility boundary changes from two inclined lines to a closed curve as the waveform width decreases. It is found that reducing the waveform width significantly improves the absorption of rf power density by the multipactor discharge.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Fluids & Plasmas
Shu Lin, Hao Qu, Patrick Wong, Peng Zhang, John Verboncoeur, Huan Zhong, Yonggui Zhai, Meng Cao, Hongguang Wang, Yongdong Li
Summary: This paper investigates the effect of electron angular momentum on the multipactor threshold of coaxial lines through an improved statistical modeling method. The results show that compared to methods that only consider radial momentum, this method provides more accurate threshold calculations for first-order multipactor and reveals significant discrepancies for higher-order multipactor.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Applied
Asif Iqbal, Daniel Wozniak, Md Ziaur Rahman, Sneha Banerjee, John Verboncoeur, Peng Zhang, Chunqi Jiang
Summary: A study was conducted on the breakdown of atmospheric air with non-uniform dc electric field in a needle-to-plate electrode configuration using a semi-analytic model and experimental measurements. The breakdown voltages for both positive and negative discharge polarities were recorded, and empirical relations between the critical avalanche size for streamer breakdown and the gap distance were proposed. A semi-analytic model based on Meek's criterion was developed to accurately predict the measured breakdown voltages. It was found that the polarity effect exists when pd > 380 Torr cm, but transitions to the inverted polarity effect when pd < 380 Torr cm.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Shu Lin, Hao Qu, Ning Xia, Patrick Wong, Peng Zhang, John Verboncoeur, Meng Cao, Yonggui Zhai, Yongdong Li, Hongguang Wang
Summary: The paper presents a thorough quantitative analysis of multipactor threshold sensitivity to secondary emission yield (SEY) variation, taking into consideration the effect of device geometry, multipactor mode, and material type. By statistical modeling, multipactor threshold voltages are calculated for different multipactor orders and materials in critical SEY regions. The study also investigates the distribution of electron impact energy to understand the underlying mechanism for the sensitivity discrepancy. The research provides useful reference for properly determining the threshold margin from the measurement error of SEY, thus optimizing performance in microwave device applications.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
De-Qi Wen, Janez Krek, Jon Tomas Gudmundsson, Emi Kawamura, Michael A. Lieberman, Peng Zhang, John P. Verboncoeur
Summary: By considering the ion-induced secondary electrons and the presence of excited state atoms, the particle-in-cell Monte Carlo collision simulations can achieve better agreement with experimental measurements for low pressure radio frequency capacitive argon plasma discharges.
PLASMA SOURCES SCIENCE & TECHNOLOGY
(2023)
Review
Engineering, Electrical & Electronic
Asif Iqbal, De-Qi Wen, John Verboncoeur, Peng Zhang
Summary: This article reviews recent progress in the prediction, characterisation, and mitigation of multipactor discharge for single- and two-surface geometries. It provides an overview of basic concepts, discusses mitigation strategies, and presents recent advances in multipactor physics and engineering. Additionally, it reviews multipactor-induced ionization breakdown and summarises the recent advances in this area.
Editorial Material
Physics, Fluids & Plasmas
Jim Browning, Nicholas M. Jordan, Jacob Stephens, Peng Zhang
IEEE TRANSACTIONS ON PLASMA SCIENCE
(2023)
Article
Physics, Applied
Lan Jin, Yang Zhou, Peng Zhang
Summary: This paper investigates the direct density modulation of high-current electron beam emission from an RF cold cathode using optical excitation. The study explores the photo-assisted field emission of periodically bunched electron beams under the combined excitation of an RF field and an optical field. The results provide insights into controlling the frequency components in beam current emission and achieving direct density modulation by optical means.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Chubin Lin, Jiandong Chen, Asif Iqbal, Peng Zhang, Yangyang Fu
Summary: A universal breakdown curve applicable to different types of gases was developed using a dimensional method to evaluate microscale gas breakdown characteristics. The breakdown mode transitioned from ion-induced secondary electron emission to the field emission regime as the gap distance decreased. Incorporating the positive space charge effect in the field emission regime was achieved by modifying the local electric field enhancement factor beta. The proposed approach simplifies the numerical model significantly and various factors such as gas pressure, gap distance, cathode properties, and electric field nonuniformity were examined.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Asif Iqbal, Brian Z. Bentz, Yang Zhou, Kevin Youngman, Peng Zhang
Summary: This article characterizes the effects of cathode photoemission leading to electrical discharges in an argon gas. The breakdown voltage is found to be lower with photoemission than without. Laser driven photoemission can create a breakdown where a sheath is formed. The effects of different applied voltages and laser energies on the breakdown voltage and current waveforms are investigated.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Yang Zhou, Peng Zhang
Summary: This study investigates the effects of DC bias field on the coherent control of quantum pathways in two-color laser photoemission using exact analytical solutions. The results show that the modulation of photoemission current can be suppressed as the DC field increases.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Shu Lin, Huan Zhong, Cheng Chen, Meng Cao, Yongdong Li, Yonggui Zhai, Patrick Y. Wong, Peng Zhang, John P. Verboncoeur
Summary: In this study, an improved 2D2V statistical modeling method is used to investigate the effect of spatial SEY discrepancy on multipactor formation in microwave devices. The research reveals that the establishment of a multipactor is dominated by electron multiplication and electron overflow in the high-SEY region, making the multipactor threshold strongly dependent on the SEY property and region size.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Applied
Yang Zhou, Ragib Ahsan, Hyun Uk Chae, Rehan Kapadia, Peng Zhang
Summary: In this paper, an exact analytical quantum theory for field emission from surfaces with a nearby quantum well is developed by solving the one-dimensional time-independent Schrodinger equation. It is found that the quantum well can lead to resonant tunneling enhanced field emission up to several orders of magnitude larger than that from bare cathode surfaces, and the electron-emission energy spectrum is significantly narrowed.
PHYSICAL REVIEW APPLIED
(2023)