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Hot-hole transport and noise phenomena in silicon at cryogenic temperatures from first principles

Physical Review B 2023年第23期108卷 235207-235207页

作者： David S. Catherall Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

The transport properties of hot holes in silicon at cryogenic temperatures exhibit several anomalous features, including the emergence of two distinct saturated drift velocity regimes and a nonmonotonic trend of the current noise versus electric field at microwave frequencies. Despite prior investigations, these features lack generally accepted explanations. Here, we examine the microscopic origin of these phenomena by extending a recently developed ab initio theory of high-field transport and noise in semiconductors. We find that the drift velocity anomaly may be attributed to scattering dominated by acoustic phonon emission, leading to an additional regime of drift velocity saturation at temperatures ∼40 K for which the acoustic phonon occupation is negligible; while the nonmonotonic trend in the current noise arises due to the decrease in momentum relaxation time with electric field. The former conclusion is consistent with the findings of prior work, but the latter distinctly differs from previous explanations. This work highlights the use of high-field transport and noise phenomena as sensitive probes of microscopic charge transport phenomena in semiconductors.

关键词： Carrier dynamics Electrical conductivity Electron relaxation Electron-phonon coupling Fluctuations & noise Transport phenomena Elemental semiconductors Boltzmann theory

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Battery-Free Wearable Electrochemical Sweat Sensors 5

Battery-Free Wearable Electrochemical Sweat Sensors

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5th IEEE International Flexible Electronics technology Conference, IFETC 2023

作者： Min, Jihong Gao, Wei California Institute of Technology Division of Engineering and Applied Science Andrew and Peggy Cherng Department of Medical Engineering PasadenaCA91125 United States

ISBN: (纸本)9798350332094

Broad adoption of wearable sensor devices that continuously and unobtrusively monitor physiochemical biomarkers can enable personalized healthcare through big data and predictive algorithms. Wearable sweat sensing offers an attractive means of biochemical screening among large populations as sweat is rich in biomarkers. However, sustainable powering of wearable sweat sensor devices is a challenge as autonomous sweat extraction, multiplexed biomarker detection, data processing, and data communication consume significant energy and typically require bulky lithium batteries. Various energy harvesting modules such as triboelectric nanogenerators (TENGs), biofuel cells (BFCs), and solar cells (SCs) have been judiciously designed and integrated into wearable platforms for battery-free analysis of sweat biomarkers. © 2023 IEEE.

关键词： Biomarkers

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Transport and noise of hot electrons in GaAs using a semianalytical model of two-phonon polar optical phonon scattering

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Physical Review B 2023年第20期107卷 205201-205201页

作者： Jiace Sun Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

Recent ab initio studies of electron transport in GaAs have reported that electron-phonon (e-ph) interactions beyond the lowest order play a fundamental role in charge transport and noise phenomena. Inclusion of the next-leading-order process in which an electron scatters with two phonons was found to yield good agreement for the high-field drift velocity, but the characteristic nonmonotonic trend of the power spectral density of current fluctuations (PSD) with electric field was not predicted. The high computational cost of the ab initio approach necessitated various approximations to the two-phonon scattering term, which were suggested as possible origins of the discrepancy. Here we report a semianalytical transport model of two-phonon electron scattering via the Fröhlich mechanism, allowing a number of the approximations in the ab initio treatment to be lifted while retaining the accuracy to within a few percent. We compare the calculated and experimental transport and noise properties as well as scattering rates measured by photoluminescence experiments. We find quantitative agreement within 15% for the drift velocity and 25% for the Γ valley scattering rates, and agreement with the Γ−L intervalley scattering rates within a factor of two. Considering these results and prior studies of current noise in GaAs, we conclude that the most probable origin of the nonmonotonic PSD trend versus electric field is the formation of space-charge domains rather than intervalley scattering as has been assumed.

关键词： Electron-phonon coupling Noise Transport phenomena Semiconductors Boltzmann theory

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Two-phonon scattering in nonpolar semiconductors: A first-principles study of warm electron transport in Si

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Physical Review B 2023年第4期107卷 L041110-L041110页

作者： Benjamin Hatanpää Alexander Y. Choi Peishi S. Cheng Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

The ab initio theory of charge transport in semiconductors typically employs the lowest-order perturbation theory in which electrons interact with one phonon (1ph). This theory is accepted to be adequate to explain the low-field mobility of nonpolar semiconductors but has not been tested extensively beyond the low-field regime. Here, we report first-principles calculations of the electric field dependence of the electron mobility of Si as described by the warm electron coefficient β. Although the 1ph theory overestimates the low-field mobility by only around 20%, it overestimates β by over a factor of two over a range of temperatures and crystallographic axes. We show that the discrepancy in β is reconciled by the inclusion of on-shell iterated two-phonon (2ph) scattering processes, indicating that scattering from higher-order electron-phonon interactions is non-negligible even in nonpolar semiconductors. Further, a ∼20% underestimate of the low-field mobility with 2ph scattering suggests that nontrivial cancellations may occur in the perturbative expansion of the electron-phonon interaction.

关键词： Electrical conductivity Electrical properties Electron-phonon coupling Electronic structure Electronic structure of atoms & molecules First-principles calculations Elemental semiconductors

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A Computationally Assisted Approach for Designing Wearable Biosensors toward Non-Invasive Personalized Molecular Analysis

A Computationally Assisted Approach for Designing Wearable B...

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2023 AIChE Annual Meeting

作者： Mukasa, Daniel Wang, Minqiang Min, Jihong Yang, Yiran Solomon, Samuel A. Han, Hong Ye, Cui Gao, Wei Department of Medical Engineering Division of Engineering and Applied Science California Institute of Technology PasadenaCA91125 United States

Wearable sweat sensors have the potential to revolutionize precision medicine as they can non-invasively collect molecular information closely associated with an individual's health status. However, the majority of clinically relevant biomarkers cannot be continuously detected in situ using existing wearable approaches. Molecularly imprinted polymers (MIPs) are a promising candidate to address this challenge but haven't yet gained widespread use due to their complex design and optimization process yielding variable selectivity. Here, QuantumDock is introduced, an automated computational framework for universal MIP development toward wearable applications. QuantumDock utilizes density functional theory to probe molecular interactions between monomers and the target/interferent molecules to optimize selectivity, a fundamentally limiting factor for MIP development toward wearable sensing. A molecular docking approach is employed to explore a wide range of known and unknown monomers, and to identify the optimal monomer/cross-linker choice for subsequent MIP fabrication. Using an essential amino acid phenylalanine as the exemplar, experimental validation of QuantumDock is performed successfully using solution-synthesized MIP nanoparticles coupled with ultraviolet-visible spectroscopy. Moreover, a QuantumDock-optimized graphene-based wearable device is designed that can perform autonomous sweat induction, sampling, and sensing. For the first time, wearable non-invasive phenylalanine monitoring is demonstrated in human subjects toward personalized healthcare applications. © 2023 American institute of Chemical Engineers. All rights reserved.

关键词： Graphene

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Realizing symmetry-protected topological phases in a spin-1/2 chain with next-nearest-neighbor hopping on superconducting qubits

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Physical Review A 2023年第3期107卷 032614-032614页

作者： Adrian T. K. Tan Shi-Ning Sun Ruslan N. Tazhigulov Garnet Kin-Lic Chan Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena California 91125 USA

Quantum simulation on near-term quantum hardware is a topic of intense interest. The preparation of novel quantum states of matter provides a quantitative assessment of the capabilities of near-term digital quantum computers to implement circuits with structure of relevance to quantum simulation. Here, we conduct a benchmark study by realizing symmetry-protected topological (SPT) phases of a spin-1/2 Hamiltonian with next-nearest-neighbor hopping on up to 11 qubits on a programmable superconducting quantum processor using adiabatic state preparation. Using recompilation techniques to reduce the gate count to around 50 two-qubit gates, we observe clear signatures of the two distinct SPT phases, such as excitations localized to specific edges and finite string-order parameters. We identify a parasitic phase associated with the two-qubit gate as the dominant imperfection that limits the depth of the circuits, indicating a research topic of interest for future hardware development.

关键词： Quantum simulation

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High-Efficiency Nanophotonic Entangled Pair Production at Visible and Near-IR Wavelengths

High-Efficiency Nanophotonic Entangled Pair Production at Vi...

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CLEO: Fundamental science. CLEO:FS 2024 - Part of Conference on Lasers and Electro-Optics, CLEO 2024

作者： Harper, Nathan A. Hwang, Emily Y. Sekine, Ryoto Ledezma, Luis Perez, Christian Marandi, Alireza Cushing, Scott K. Division of Chemistry and Chemical Engineering California Institute of Technology PasadenaCA91125 United States Department of Applied Physics and Materials Science California Institute of Technology PasadenaCA91125 United States Department of Electrical Engineering California Institute of Technology PasadenaCA91125 United States California State University Los Angeles90032 United States

We demonstrate nanophotonic visible and near-IR entangled photon pair production via periodically poled thin-film lithium niobate waveguides. Pairs spanning 720-900 nm are generated from 405-406.4 nm pump wavelengths ... 详细信息

ISBN: (纸本)9781957171395

关键词： Quantum entanglement

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Stretch-inactivated ion transport through subnanoporous two-dimensional membranes

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Physical Review Materials 2024年第10期8卷 L103001页

作者： Yechan Noh Alex Smolyanitsky Department of Physics University of Colorado Boulder Boulder 80309 CO United States Applied Chemicals and Materials Division National Institute of Standards and Technology Boulder 80305 CO United States Department of Materials Science and Engineering University of California Berkeley Berkeley 94720 CA United States

In biology, mechanosensitive ion channels facilitate the conversion of mechanical stimuli, such as sound and touch, into electrical signals. Similar functionality in artificial systems was recently predicted in the form of stretch-activated transport through porous 2D membranes. Here we describe an opposite behavior, in which ion transport is inactivated upon stretching a subnanoporous 2D membrane. We explore electrophoretic ion transport through several subnanoporous membranes using molecular dynamics simulations. We demonstrate that aqueous K+ transport decreases by a factor of 3–8 under stretching of order 3%. In contrast, Na+ ions exhibit transport activation by stretching, suggesting ion-dependent activation and inactivation in a single membrane. Our analysis shows that inactivation of K+ transport is caused by a strain-induced repulsive-to-attractive transition in the K+-pore interactions due to alignment of the local energy minima.

关键词： Chemical Physics & Physical Chemistry Complex systems Ionic transport Membranes Solvation 2-dimensional systems Molecular dynamics

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Quasi-Lindblad pseudomode theory for open quantum systems

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Physical Review B 2024年第19期110卷 195148-195148页

作者： Gunhee Park (박건희) Zhen Huang Yuanran Zhu Chao Yang Garnet Kin-Lic Chan Lin Lin Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA Department of Mathematics University of California Berkeley California 94720 USA Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena California 91125 USA

We introduce a new framework to study the dynamics of open quantum systems with linearly coupled Gaussian baths. Our approach replaces the continuous bath with an auxiliary discrete set of pseudomodes with dissipative dynamics, but we further relax the complete positivity requirement in the Lindblad master equation and formulate a quasi-Lindblad pseudomode theory. We show that this quasi-Lindblad pseudomode formulation directly leads to a representation of the bath correlation function in terms of a complex weighted sum of complex exponentials, an expansion that is known to be rapidly convergent in practice and thus leads to a compact set of pseudomodes. The pseudomode representation is not unique and can differ by a gauge choice. When the global dynamics can be simulated exactly, the system dynamics is unique and independent of the specific pseudomode representation. However, the gauge choice may affect the stability of the global dynamics, and we provide an analysis of why and when the global dynamics can retain stability despite losing positivity. We showcase the performance of this formulation across various spectral densities in both bosonic and fermionic problems, finding significant improvements over conventional pseudomode formulations.

关键词： Open quantum systems Open quantum systems & decoherence Strongly correlated systems Anderson impurity model Lindblad equation Non-Markovian processes Nonperturbative methods Spin-boson model

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FAST AND ROBUST METHOD FOR SCREENED POISSON LATTICE GREEN'S FUNCTION USING ASYMPTOTIC EXPANSION AND FAST FOURIER TRANSFORM

arXiv

引用

arXiv 2024年

作者： Hou, Wei Colonius, Tim Division of Engineering and Applied Science California Institute of Technology United States

We study the lattice Green's function (LGF) of the screened Poisson equation on a two-dimensional rectangular lattice. This LGF arises in numerical analysis, random walks, solid-state physics, and other fields. Its defining characteristic is the screening term, which defines different regimes. When its coefficient is large, we can accurately approximate the LGF with an exponentially converging asymptotic expansion, and its convergence rate monotonically increases with the coefficient of the screening term. To tabulate the LGF when the coefficient is not large, we derive a one-dimensional integral representation of the LGF. We show that the trapezoidal rule can approximate this integral with exponential convergence, and we propose an efficient algorithm for its evaluation via the Fast Fourier Transform. We discuss applications including computing the LGF of the three-dimensional Poisson equation with one periodic direction and the return probability of a two-dimensional random walk with killing. Copyright © 2024, The Authors. All rights reserved.

关键词： Fast Fourier transforms

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