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Mean free path

About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.


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Journal ArticleDOI
C.R. Crowell1, S. M. Sze
TL;DR: In this article, the authors investigated the temperature dependence of the carrier mean free path for optical phonon scattering and the mean energy loss per collision for any operating temperature once the appropriate parameters have been determined.
Abstract: Expressions for the temperature dependence of the carrier mean free path for optical phonon scattering and the mean energy loss per collision are presented which predict avalanche multiplication as a function of electric field for any operating temperature once the appropriate parameters have been determined at a single temperature. This has been verified for electrons in Si by the correlation of measurements at 300°K, 213°K, and 100°K. The temperature dependence of the breakdown voltages of a variety of abrupt and linear‐graded Si and Ge p‐n junctions has also been predicted. The fractional change in breakdown voltage with increasing temperature is predicted to decrease with increased doping concentration and, for the same breakdown voltage, to be less for linear‐graded junctions than for abrupt junctions.

419 citations

Journal ArticleDOI
TL;DR: In this article, a geometrical probability measure is proposed for calculating the effective conduction electron mean free path of an arbitrary shape convex particle, which is shown to be consistent with exact quantum mechanical widths for simple particle shapes.
Abstract: A geometrical probability measure is proposed for calculating the effective conduction electron mean free path of an arbitrary shape convex particle. It is shown that the plasmon widths determined from this mean free path are consistent with exact quantum mechanical widths for simple particle shapes. We use the mean free path formula to evaluate size and shape dependent dielectric functions and extinction spectra for silver spheroids, square prisms, truncated tetrahedrons, and cylinders.

410 citations

Journal ArticleDOI
TL;DR: In this article, the authors calculate the density spectrum in turbulent magnetized plasmas by extending the theory of incompressible magnetohydrodynamic (MHD) turbulence given by Goldreich & Sridhar to include the effects of compressibility and particle transport.
Abstract: Radio wave scintillation observations reveal a nearly Kolmogorov spectrum of density fluctuations in the ionized interstellar medium. Although this density spectrum is suggestive of turbulence, no theory relevant to its interpretation exists. We calculate the density spectrum in turbulent magnetized plasmas by extending the theory of incompressible magnetohydrodynamic (MHD) turbulence given by Goldreich & Sridhar to include the effects of compressibility and particle transport. Our most important results are as follows: 1. Density fluctuations are due to the slow mode and the entropy mode. Both modes are passively mixed by the cascade of shear Alfven waves. Since the shear Alfven waves have a Kolmogorov spectrum, so do the density fluctuations. 2. Observed density fluctuation amplitudes constrain the nature of MHD turbulence in the interstellar medium. Slow mode density fluctuations are suppressed when the magnetic pressure is less than the gas pressure. Entropy mode density fluctuations are suppressed by cooling when the cascade timescale is longer than the cooling timescale. These constraints imply either that the magnetic and gas pressures are comparable or that the outer scale of the turbulence is very small. 3. A high degree of ionization is required for the cascade to survive damping by neutrals and thereby to extend to small length scales. Regions that are insufficiently ionized produce density fluctuations only on length scales larger than the neutral damping scale. These regions may account for the excess of power that is found on large scales. 4. Provided that the thermal pressure exceeds the magnetic pressure, both the entropy mode and the slow mode are damped on length scales below that at which protons can diffuse across an eddy during the eddy's turnover time. Consequently, eddies whose extents along the magnetic field are smaller than the proton collisional mean free path do not contribute to the density spectrum. However, in MHD turbulence eddies are highly elongated along the magnetic field. From an observational perspective, the relevant length scale is that transverse to the magnetic field. Thus, the cutoff length scale for density fluctuations is significantly smaller than the proton mean free path. 5. The Alfven mode is critically damped at the transverse length scale of the proton gyroradius and thus cascades to smaller length scales than either the slow mode or the entropy mode.

400 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point fermion material, and they showed that the electrical resistivity is 6 nΩ cm at 2'K with a large mean free path of 11 microns.
Abstract: Weyl and Dirac fermions have created much attention in condensed matter physics and materials science. Recently, several additional distinct types of fermions have been predicted. Here, we report ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point fermion material. We show that the electrical resistivity is 6 nΩ cm at 2 K with a large mean free path of 11 microns. de Haas-van Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to noble metals with similar conductivity and number of carriers, the magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the momentum relaxing time of the electrons is found to be more than 15 times larger than the quantum coherence time. This difference between the scattering scales shows that momentum conserving scattering dominates in MoP at low temperatures. Although novel topological quasiparticles have recently been evidenced, their electrical transport properties remain elusive. Here, the authors report ultra-low resistivity down to 6 nΩcm at 2 K in MoP with a large mean free path, which hints on the exotic properties of triple point fermions.

392 citations

Journal ArticleDOI
TL;DR: In this paper, the optical properties of nanosized silver particles self-assembled in a 2D or 3D network were investigated. But the optical property of the self-assembly was not investigated.
Abstract: In this paper we compare the optical properties of nanosized silver particles dispersed in hexane solution and self-assembled in a 2D or 3D network. When the particles form monolayers organized in a hexagonal network, the plasmon peak of silver nanosized particles is shifted toward lower energy, with an increase in bandwidth compared to that observed with free coated particles dispersed in hexane solution. Such a shift is attributed to an increase in the dielectric constant of the matrix environment of the nanoparticles. When the particles form a 3D superlattice with a face-centered cubic (fcc) structure, the optical properties could be interpreted as an increase in the mean free path of the conduction electrons, which could indicate the presence of tunneling electrons across the double layers due to the coating of the particles.

373 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202375
2022207
2021134
2020114
2019113
201887