اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe Effect of Dissipation on the Torque and Force Experienced by Nanoparticles in an AC Field
179
0
0.0
(
0
)
تأليف
F. Claro
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We discuss the force and torque acting on spherical particles in an ensemble in the presence of a uniform AC electric field. We show that for a torque causing particle rotation to appear the particle must be absorptive. Our proof includes all electromagnetic excitations, which in the case of two or more particles gives rise to one or more resonances in the spectrum of force and torque depending on interparticle distance. Several peaks are found in the force and torque between two spheres at small interparticle distances, which coalesce to just one as the separation grows beyond three particle radii. We also show that in the presence of dissipation the force on each particle is non conservative and may not be derived from the classical interaction potential energy as has been done in the past.
قيم البحث
اقرأ أيضاً
The phenomenon of spin transfer torque (STT) has attracted a great deal of interests due to its promising prospects in practical spintronic devices. In this paper, we report a theoretical investigation of STT in a noncollinear magnetic tunnel junctio
n under ac modulation based on the nonequilibrium Greens function formalism, and derive a closed-formulation for predicting the time-averaged STT. Using this formulation, the ac STT of a carbon-nanotube-based magnetic tunnel junction is analyzed. Under ac modulation, the low-bias linear (quadratic) dependence of the in-plane (out-of-plane) torque on bias still holds, and the $sintheta$ dependence on the noncollinear angle is maintained. By photon-assisted tunneling, the bias-induced components of the in-plane and out-of-plane torques can be enhanced significantly, about 12 and 75 times, respectively. Our analysis reveals the condition for achieving optimized STT enhancement and suggests that ac modulation is a very effective way for electrical manipulation of STT.
This paper reports results of the computation of the drag force exerted on an oscillating object in quantum turbulence in superfluid $^4$He. The drag force is calculated on the basis of numerical simulations of quantum turbulent flow about the object
. The drag force is proportional to the square of the magnitude of the oscillation velocity, which is similar to that in classical turbulence at high Reynolds number. The drag coefficient is also calculated, and its value is found to be of the same order as that observed in previous experiments. The correspondence between quantum and classical turbulences is further clarified by examining the turbulence created by oscillating objects.
We address the issue of inter-particle dipolar interactions in the context of magnetic hyperthermia. More precisely, the main question dealt with here is concerned with the conditions under which the specific absorption rate is enhanced or reduced by
dipolar interactions. For this purpose, we propose a theory for the calculation of the AC susceptibility, and thereby the specific absorption rate, for a monodisperse two-dimensional assembly of nanoparticles with oriented anisotropy, in the presence of a DC magnetic field, in addition to the AC magnetic field. We also study the competition between the dipolar interactions and the DC field, both in the transverse and longitudinal configurations. In both cases, we find that the specific absorption rate has a maximum at some critical DC field that depends on the inter-particle separation. In the longitudinal setup, this critical field falls well within the range of experiments.
This is a brief overview of the main physical ideas for application of field effect transistors for generation and detection of TeraHertz radiation. Resonant frequencies of the two-dimensional plasma oscillations in FETs increase with the reduction o
f the channel dimensions and reach the THz range for sub-micron gate lengths. When the mobility is high enough, the dynamics of a short channel FET at THz frequencies is dominated by plasma waves. This may result, on the one hand, in a spontaneous generation of plasma waves by a dc current and on the other hand, in a resonant response to the incoming radiation. In the opposite case, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector.
A topologically equivalent tight binding model is proposed to study the quantum phase transitions of dimer chain driven by an imaginary ac field. I demonstrate how the partner Hamiltonian is constructed by a similarity transformation to fulfil the $m
athcal{PT}$ symmetry. The $mathcal{PT}$ symmetry of the partner model allows us to study the topological properties of the original non-Hermitian model as the Bloch bands of the Hermitian system. The quantum phase transitions are discussed in different frequency regime. The approach has the potential applications to investigate the topological states of matter driven by the complex external parameters.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
