Absorption refrigerators transfer thermal energy from a cold bath to a hot bath without input power by utilizing heat from an additional "work" reservoir. Particularly interesting is a three-level design for a quantum absorption refrigerator, which can be optimized to reach the maximal (Carnot) cooling efficiency. Previous studies of three-level chillers focused on the behavior of the averaged cooling current. Here, we go beyond that and study the full counting statistics of heat exchange in a three-level chiller model. We explain how to obtain the complete cumulant generating function of the refrigerator in a steady state, then derive a partial cumulant generating function, which yields closed-form expressions for both the averaged cooling current and its noise. Our analytical results and simulations are beneficial for the design of nanoscale engines and cooling systems far from equilibrium, with their performance optimized according to different criteria, efficiency, power, fluctuations, and dissipation.
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http://dx.doi.org/10.1103/PhysRevE.97.052145 | DOI Listing |
Nanoscale
January 2025
Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China.
Two-dimensional materials with a combination of a moderate bandgap, highly anisotropic carrier mobility, and a planar structure are highly desirable for nanoelectronic devices. This study predicts a planar BeP monolayer with hexagonal symmetry that meets the aforementioned desirable criteria using the CALYPSO method and first-principles calculations. Calculations of electronic properties demonstrate that the hexagonal BeP monolayer is an intrinsic semiconductor with a direct band gap of approximately 0.
View Article and Find Full Text PDFACS Nano
January 2025
Center for Terahertz Waves and School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
The physical picture for photocurrent injection and coherent control in intrinsic graphene under two-color laser excitation remains obscure. Previously, photocurrent injection of intrinsic graphene was attributed to the quantum interference between two electronic transition pathways of single-photon and two-photon absorptions as well as layer-to-layer coupling. Here, we show that quantum interference between stimulated electronic Raman scattering and single-photon absorption plays a very important role in contributing to the total photocurrent, while interlayer coupling does not sufficiently affect the photocurrent injection, which is in contrast to the previous interpretation of the experimental results on photocurrent injection and coherent control.
View Article and Find Full Text PDFChemistry
January 2025
Institute of Organic Chemistry PAS: Instytut Chemii Organicznej Polskiej Akademii Nauk, Institute of Organic Chemistry, Kasprzaka 44/52, 01-224, Warsaw, POLAND.
Herein, we report the synthesis and chiroptical characteristics of the first (double) helicenes possesing the 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP) moiety as their central core. We have developed a three-step synthesis with 6π-electrocyclization accompanied with HBr elimination as its key step. We found that, whereas for smaller periphereal arms double 6π-electrocyclization occurs smoothly forming a double helicene, in the case of longer policyclic aromatic hydrocarbons the reaction becomes less efficient and mono-helicenes are the only products.
View Article and Find Full Text PDFAnal Sci
January 2025
MOE Key Laboratory of Resources and Environmental System Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, People's Republic of China.
As one of the most harmful heavy metal pollutants, hexavalent chromium Cr(VI) is becoming a serious threat to human health. Thus pursuing a remarkably sensitive method to monitor the Cr(VI) concentration in natural conditions is favored for the fast response to prevent harm. In the present work, an ethylenediamine (En) and SiO-modified wool keratin-based carbon quantum dot (CQD)(En@CQDs@SiO) fluorescent sensor is prepared, and the En is found to improve the discrimination ability by binding the Cr(VI) with the surface carboxyl groups.
View Article and Find Full Text PDFChem Asian J
January 2025
Universite de Rennes 1, Sciences Chimiques de Rennes - UMR 6226, Avenue du General Leclerc, Campus de Beaulieu, 35042, Rennes, FRANCE.
A novel coordination motif comprising [4]helicene fused with pyrazino-phenanthroline (H4PP) has been synthesized and reacted with ReCl(CO)5 to yield its rhenium(I) complex (Re-H4PP). Absorption and emission spectroscopic analysis conducted in dichloromethane and 2-methyltetrahydrofuran reveals that combining pyrazino-phenanthroline with helicene visibly affects the photophysical attributes of both the resulting ligand and its Re(I) complex as compared to their non-helicene analogues, and even more importantly leads to relatively high photoluminescence quantum yield values, especially in the case of H4PP (29%). Chiroptical studies through electronic circular dichroism and circularly polarized luminescence performed on enantiomerically enriched samples of Re-H4PP show the chiral nature of low-energy excited states affording notable glum values that amplify at cryogenic temperatures.
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