共查询到20条相似文献,搜索用时 0 毫秒
1.
The oblique impacts of nanoclusters are studied theoretically and by means of molecular dynamics. In simulations we explore two models--Lennard-Jones clusters and particles with covalently bonded atoms. In contrast with the case of macroscopic bodies, the standard definition of the normal restitution coefficient yields for this coefficient negative values for oblique collisions of nanoclusters. We explain this effect and propose a proper definition of the restitution coefficient which is always positive. We develop a theory of an oblique impact based on a continuum model of particles. A surprisingly good agreement between the macroscopic theory and simulations leads to the conclusion that macroscopic concepts of elasticity, bulk viscosity, and surface tension remain valid for nanoparticles of a few hundred atoms. 相似文献
2.
3.
4.
We show that the transition to nondegeneracy induced in a semiconductor at very low temperatures by a sufficiently strong magnetic field should give rise to an anomalous behavior of the Nernst-Ettingshausen coefficient. 相似文献
5.
Langevin simulations provide an effective way to study collective effects of Brownian particles immersed in a two-dimensional periodic potential. In this paper, we concentrate essentially on the behaviour of the tracer (DTr) and collective diffusion coefficients (DC) as function of friction (Γ). Our simulations show that in the high friction limit, the two physical quantities DTr and DC present qualitatively the same behaviour, for both coupled and decoupled substrate potentials. However, for the low friction regime, and especially for the coupled potential case, an anomalous diffusion behaviour is found where DTr∼Γ-σTr and DC∼Γ-σC, with σTr<σC<1. We also found that in the case of weak dynamical coupling between the adparticles and the substrate, the exponents are not universal and rather depend on the potentials. Moreover, changes in the inter-particle potentials may reverse the behaviour to a normal one. 相似文献
6.
7.
8.
9.
10.
11.
M. Tachiki A. Kotani S. Takahashi T. Koyama H. Matsumoto H. Umezawa 《Solid State Communications》1981,37(2):113-117
The effect of the electromagnetic interaction between the persistent current and the magnetic moments to the surface state in ferromagnetic superconductors is studied theoretically. This interaction causes an oscillatory decay of the penetrated magnetic field near the magnetic phase transition temperature. Below a critical temperature, the spontaneous surface magnetization is stabilized by the magnetic field induced by the surface persistent current. 相似文献
12.
An anomalous temperature dependence in the normal-state electronic attenuation in Nb is investigated. The effect is found to scale with ql. Models for the effect are considered. 相似文献
13.
We report studies on temperature, field and time dependence of magnetization on cupric oxide nanoparticles of sizes 9 nm, 13 nm and 16 nm. The nanoparticles show unusual features in comparison to other antiferromagnetic nanoparticle systems. The field cooled (FC) and zero field cooled (ZFC) magnetization curves bifurcate well above the Néel temperature and the usual peak in the ZFC magnetization curve is absent. The system does not show any memory effects which is in sharp contrast to the usual behavior shown by other antiferromagnetic nanoparticles. It turns out that the non-equilibrium behavior of CuO nanoparticles is very strange and is neither superparamagnetic nor spin glass like. 相似文献
14.
15.
Ruiz-Fuertes J Segura A Rodríguez F Errandonea D Sanz-Ortiz MN 《Physical review letters》2012,108(16):166402
High-pressure optical-absorption measurements performed in CuWO(4) up to 20 GPa provide experimental evidence of the persistence of the Jahn-Teller (JT) distortion in the whole pressure range both in the low-pressure triclinic and in the high-pressure monoclinic phase. The electron-lattice couplings associated with the e(g)(E?e) and t(2g)(T?e) orbitals of Cu(2+) in CuWO(4) are obtained from correlations between the JT distortion of the CuO(6) octahedron and the associated structure of Cu(2+) d-electronic levels. This distortion and its associated JT energy (E(JT)) decrease upon compression in both phases. However, both the distortion and associated E(JT) increase sharply at the phase-transition pressure (P(PT)=9.9 GPa), and we estimate that the JT distortion persists for a wide pressure range not being suppressed up to 37 GPa. These results shed light on the transition mechanism of multiferroic CuWO(4), suggesting that the pressure-induced structural phase transition is a way to minimize the distortive effects associated with the toughness of the JT distortion. 相似文献
16.
A. Tsukernik D. Cheskis O. Potashnik A. Palevski S. Bar-Ad S. Luryi A. Cho 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):341-344
We have measured the dependence of the Fermi energy on carrier concentration in Sn doped InGaAs at 4.2 K and 300 K. At 4.2
K the Fermi energy was measured by photoluminescence spectroscopy, and at 300 K it was deduced from transport measurements
of thermionic emission. In both cases the dependence of the Fermi energy on the mobile electron concentration, measured by
Hall effect, strongly deviates from standard theoretical predictions, and the deviation increases with concentration. The
most striking observed anomaly is the near saturation of the Fermi level when the Hall concentration exceeds 1019 cm-3.
Received 19 April 2001 and Received in final form 22 July 2001 相似文献
17.
It is shown that a qualitatively new type of transition to a nonlinear phase is possible in two-dimensional two-phase textures
in a magnetic field. The anomalous growth of the effective response (higher-order correlation functions of the current) near
the critical magnetic field is studied. The dependence of the critical magnetic field on the angles of microinclusions is
calculated.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 2, 115–119 (25 July 1997) 相似文献
18.
In contact with a superconductor, the Andreev reflection of the electrons locally modifies the N metal electronic properties,
including the local density of states (LDOS). We investigated the LDOS in superconductor-normal metal (Nb-Au) bilayers using
a very low temperature (60 mK) STM on the normal metal side. High resolution tunneling spectra measured on the Au surface
show a clear proximity effect with an energy gap of reduced amplitude compared to the bulk Nb gap. The dependence of this
mini-gap width with the normal metal thickness is discussed in terms of the Thouless energy. Within the mini-gap, the density
of states does not reach zero and shows clear sub-gap features. We compare the experimental spectra with the well-established
quasi-classical theory. 相似文献
19.
It is an important issue to clarify the minimum required size of a specimen for the accurate measurement of oblique incidence absorption coefficient. Investigation is made on the basis of experimental studies in a laboratory, using Aoshima's time stretched pulse technique. Measurements are carried out for glass fiber with thickness of 50 and 100 mm as highly absorbing materials and for ceramic with a thickness of 52 mm as relatively low absorbing material. The tested surface areas range from 0.0625 to 42 m2 for glass fiber and from 0.1563 to 39.168 m2 for ceramics. The absorption coefficients are determined at incidence angles from 0 to 45° in increments of 15°. With consideration of an active surface bounded by ellipse orbit, the minimum required surface area is 16 m2 with a ratio of length to width of about 1.25. This value is twice the area size of the active surface, which is calculated from the geometry of source and microphone, and the width of the temporal window. 相似文献
20.
A. Ya. Mal’tsev 《Journal of Experimental and Theoretical Physics》1997,85(5):934-942
The behavior of the electrical conductivity tensor in strong magnetic fields in the presence of unclosed quasiclassical electron
trajectories of complex form near the Fermi surface is considered. It is shown that the asymptotic behavior of the conductivity
tensor in the limit B→∞ differs in this case from the picture previously described for trajectories of simpler form. The possibility of blocking
the longitudinal conductivity in strong magnetic fields at low temperatures in the case of a Fermi surface of special form
is also treated theoretically.
Zh. éksp. Teor. Fiz. 112, 1710–1726 (November 1997) 相似文献