排序方式: 共有38条查询结果,搜索用时 31 毫秒
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In the only measurement to date of the ratio Rd of depolarized to polarized light scattering intensities in the isotropic phase of a cholesteric liquid crystal, Harada and Crooker reported that the value of ¾ predicted by the order parameter fluctuation theory of de Gennes was not observed. We present here measurements of Rd in cholesteryl olevl carbonate (COC) using a more precise rotating polarizer technique. Rd is observed to have a strong temperature dependence which we can explain by the de Gennes theory plus an additional fluctuating component as described by Courtens. 相似文献
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Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the nearest-neighbor "spin ice" model. We discuss the dipolar energy scale present in both these materials and discuss how spin-ice behavior can occur despite the presence of long-range dipolar interactions. We present results of numerical simulations and a mean field analysis of Ising pyrochlore systems. Based on our quantitative theory, we suggest that the spin-ice behavior in these systems is due to long-range dipolar interactions, and that the nearest-neighbor exchange in Dy2Ti2O7 is antiferromagnetic. 相似文献
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D. A. Andronikov M. Fehr V. P. Kochereshko S. A. Crooker G. Karczewski 《Physics of the Solid State》2007,49(8):1567-1571
The temperature-induced variations in the photoluminescence spectra measured in a magnetic field of trions and excitons in CdTe/CdMgTe quantum wells with modulated doping are studied. It is found that the temperature-induced redistribution of the intensity between the exciton and trion emission lines in a magnetic field is opposite to that expected from the simple Boltzmann distribution model. Coupled rate equations for the trion-exciton system are solved to construct the temperature dependences of the exciton and trion emission line intensities. The relations thus calculated are in good agreement with experiment. 相似文献
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In order to further understand the structure of the blue phase III (BPIII) phase of chiral liquid crystals, we have observed the effect of electric fields on the reflectivity of BPIII phases in which the liquid crystal has negative dielectric anisotropy. The reflectivity increases dramatically with increasing field, in contrast to the behaviour for materials of positive dielectric anisotropy. We compare the data with cubic domain and double-twist models for BPIII structure and we find that the data best agree with the double-twist model and possibly with an O5 cubic domain model. 相似文献
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S. Zaric G.N. Ostojic J. Shaver J. Kono X. Wei M. Furis S.A. Crooker O. Portugall P.H. Frings G.L.J.A. Rikken V.C. Moore R.H. Hauge R.E. Smalley 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):469
We review our recent optical experiments on single-walled carbon nanotubes in high magnetic fields. The data revealed magnetic-field-induced optical anisotropy as well as broadening, splittings, and shifts of interband absorption and photoluminescence peaks. Quantitative comparison with theoretical predictions based on the Aharonov–Bohm effect is presented. 相似文献
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Lou X Adelmann C Furis M Crooker SA Palmstrøm CJ Crowell PA 《Physical review letters》2006,96(17):176603
We show that the accumulation of spin-polarized electrons at a forward-biased Schottky tunnel barrier between Fe and -GaAs can be detected electrically. The spin accumulation leads to an additional voltage drop across the barrier that is suppressed by a small transverse magnetic field, which depolarizes the spins in the semiconductor. The dependence of the electrical accumulation signal on magnetic field, bias current, and temperature is in good agreement with the predictions of a drift-diffusion model for spin-polarized transport. 相似文献
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