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41.
We review the recent experimental progress towards observing quantum spin Hall effect in inverted InAs/GaSb quantum wells (QWs). Low temperature transport measurements in the hybridization gap show bulk conductivity of a non-trivial origin, while the length and width dependence of conductance in this regime show strong evidence for the existence of helical edge modes proposed by Liu et al. [Phys. Rev. Lett., 2008, 100: 236601]. Surprisingly, edge modes persist in spite of comparable bulk conduction and show only weak dependence on magnetic field. We elucidate that seeming independence of edge on bulk transport comes due to the disparity in Fermi-wave vectors between the bulk and the edge, leading to a total internal reflection of the edge modes. 相似文献
42.
43.
Polarized spin transport in mesoscopic quantum rings with electron--phonon and Rashba spin--orbit coupling 下载免费PDF全文
The influence of electron--phonon (EP) scattering on spin
polarization of current output from a mesoscopic ring with Rashba
spin--orbit (SO) interaction is numerically investigated. There are
three leads connecting to the ring at different positions;
unpolarized current is injected to one of them, and the other two
are output channels with different bias voltages. The spin
polarization of current in the outgoing leads shows oscillations as a
function of EP coupling strength owing to the quantum interference
of EP states in the ring region. As temperature increases, the
oscillations are evidently suppressed, implying decoherence of
the EP states. The simulation shows that the magnitude of polarized
current is sensitive to the location of the lead. The polarized
current depends on the connecting position of the lead in a
complicated way due to the spin-sensitive quantum interference
effects caused by different phases accumulated by transmitting
electrons with opposite spin states along different paths. 相似文献
44.
The magnetization of mixed spin-1/2, 1 Ising diamond chain with antiferromagnetic spin exchange interaction has been investigated by using the Monte Carlo simulation. Magnetization behaviors with different antiferromagnetic interactions are simulated under magnetic field at low temperature. The behaviors are studied in two different cases. In one case the absolute value of the interaction between two spin-1/2 atoms is the largest and in the other case it is not the largest. Multiple plateaus of magnetization M, such as plateaus at M=±1, M=0 and M=±0.566 are obtained. The plateaus at M=±0.566 correspond to two metastable states. The M=0 plateau may disappear at some specific values of spin exchange interactions. The spin configurations were checked when the plateaus appear. The dimmer and trimmer states are found. 相似文献
45.
Magnesium aluminate doped with Tb3+ (MgAl2O4:Tb3+) was prepared by combustion synthesis. Three thermoluminsence (TL) peaks at 120, 220 and 340 °C were observed. PL and TL emission spectrum shows that Tb3+ acts as the luminescent centre. Optically stimulated luminescence (OSL) was observed when stimulated by 470 nm blue light.Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the TL and OSL processes in MgAl2O4:Tb3+. Two defect centres were identified in irradiated MgAl2O4:Tb3+ phosphor by ESR measurements which was carried out at room temperature and these were assigned to V and F+ centres. V centre (hole centre) is correlated to 120 and 220 °C TL peaks and F+ centre (electron centre), which acts as a recombination centre is correlated to 120, 220 and 340 °C. 相似文献
46.
A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The electron beam size is derived by unfolding the radiation image and the point spread function (PSF) with deconvolution techniques. The performance of the pinhole is determined by the accuracy of the PSF measurement. This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes. Applying this method at SSRF, the PSF value of the pinhole is revised from 37 to 44 μm. The deviation in beam size between the theoretical value and the measured value is minimized to 4% after calibration. This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5 μm. 相似文献
47.
蛋白质的三维结构在很多情况下不能很好地解释其在生理过程中的作用机制. 动力学研究能够获悉蛋白质在不同时间尺度下的内运动信息,建立起动态结构和生物功能的联系. 该文综述了通过NMR自旋弛豫技术研究蛋白质动力学的原理和方法:ps~ns的快运动分析主要采用约化谱密度函数映射和Modelfree方法;μs~ms的慢运动涉及化学/构象交换过程,常借助CPMG和R1ρ弛豫色散手段. 基于NMR的蛋白质动力学研究,将蛋白质科学从三维空间结构推进到四维时空结构的新层面. 相似文献
48.
Exchange coupling and helical spin order in the triangular lattice antiferromagnet CuCrO<sub>2</sub> using first principles 下载免费PDF全文
The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approximations (GGA)+U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte-Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non-collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with (110) spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a + b directions, each with a screw-rotation angle of about 120°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure. 相似文献
49.
Andrej Staško Maroš Bella Ján Rimarčík Zuzana Barbieriková Viktor Milata Vladimír Lukeš Vlasta Brezová 《Journal of Physical Organic Chemistry》2012,25(8):643-648
Photoinduced reactions of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid (SeQCA) were investigated in alkaline media (aqueous NaOH solutions) by electron paramagnetic resonance (EPR) spectroscopy, following the in situ formation of paramagnetic species. According to UV–Vis and nuclear magnetic resonance investigations, protonation (pH ≈ 11) and deprotonation (pH ≈ 13) of the imino hydrogen of the 4‐pyridone moiety has to be considered, reflected also in the different EPR spectra observed upon irradiation. Photoinduced generation of radicals was found only for carboxylate substituted SeQCA; other studied selenadiazoloquinolone derivatives, together with those substituted at the C(8) position (R = H, COOCH2CH3, COOCH3, COCH3 or CN), did not generate paramagnetic species during exposure. Consequently, photodecarboxylation was suggested as the decisive step, accompanied by the decomposition of the selenadiazole ring, resulting in the formation of ortho‐hydroxylate anions. EPR parameters elucidated from experimental EPR spectra obtained at pH ≈ 11 and pH ≈ 13 indicate the formation of oxygen‐centered radicals at the decarboxylated 4‐pyridone ring. EPR spin trapping experiments with nitromethane confirmed a very effective photoinduced electron transfer from all the selenadiazoloquinolones investigated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
50.
Y. Miyachi 《中国物理 C》2010,34(9):1494-1497
The HERMES measured azimuthal amplitudes of cross sections and their transverse target single spin asymmetries for hadron productions in semi-inclusive deep inelastic scattering.From the extracted amplitudes,novel parton distribution functions can be studied.The recent results related to Sivers and Boer-Mulders distribution functions are discussed. 相似文献