排序方式: 共有58条查询结果,搜索用时 9 毫秒
41.
In this work we summarize the results of first-principles theoretical studies of the sequence of pressure-driven phase-transitions followed by the group-IVa elements Si and Ge. The agreement with the available experimental data is very good. 相似文献
42.
Chuanzhong Chen Diangang Wang Quanhe Bao Liang Zhang Tingquan Lei 《Applied Surface Science》2005,250(1-4):98-103
In this paper, the plasma sprayed coatings were treated by laser remelting. The morphologies, elements analysis and phases of both sprayed and remelted coatings were studied by means of electron probe microanalysis (EPMA), X-ray diffraction (XRD) and so on. The results show that the structure of the sprayed coatings is coarse, the amorphization of HA is tremendous, and the bonding state between the coating and the substrate is mechanical combination. After the sprayed coatings were treated by laser remelting in a proper conditions, the properties of the coatings are improved greatly. The microstructure of remelted coatings is columnar and cellular dendritic crystal which is homogeneous and compact, and the coating consists of HA, -TCP and CaO phases, the Ca/P ratio of transition layer is close to 1.67, but the Ca/P ratio of surface layer is higher than that of HA because of the loss of P. 相似文献
43.
合成了上缘特丁基脱去的杯[4]芳烃25,27-二丁氧基-26,28-二(ω-十一碳烯氧基)杯[4]芳烃(p-H-C[4]B)及其相应的聚硅氧烷化高分子(PSO-p-H-C[4]B),以有上缘用N,N-二乙基氨甲基取代的杯[4]芳烃5,11,17,23-四(N,N-二乙基氨甲基)-25,26,27,28-四(ω-十一碳烯氧基)杯[4]芳烃(p-DEAM-C[4]U),并首次将它们用作毛细管柱气相色谱固定液,涂制成色谱柱,考察了这些杯[4]芳烃色谱柱的性能。结果表明,研制的杯[4]芳烃柱对芳香位置异构体均有良好的分离能力。 相似文献
44.
We introduce a two dimensional nonlinear XY model with a second order phase transition driven by spin waves, together with a first order phase transition in the bond variables between two “bond ordered phases”, one with local ferromagnetic order and another with local anti-ferromagnetic
order. We also prove that at the transition temperature the bond-ordered phases coexist with a disordered phase as predicted
by Domany, Schick and Swendsen [1]. This last result generalizes the result of van Enter and Shlosman [2] We argue that these
phenomena are quite general and should occur for a large class of potentials.
PACS number: 64.60.Cn, 75.10.Hk 相似文献
45.
《Comptes Rendus Physique》2014,15(1):40-47
Where are we now, 25 years after the discovery of the first stable decagonal quasicrystal (DQC)? In this critical review, the status of research into these axial quasicrystals, which are quasiperiodic in two dimensions and periodic along the third, is discussed, and some of the open questions are addressed. We conclude that the structures of DQC are essentially known now, a few of them even as a function of temperature. Some hypotheses concerning DQC formation, growth and stability have still to be confirmed. 相似文献
46.
47.
《Comptes Rendus Physique》2014,15(1):12-17
Historically, two principal approaches exist to determine the quasicrystal atomic structures: one is derived directly from diffraction experiments, using cut and projection of higher dimensional space-representation techniques; the other one takes use of the similarity between so-called approximant crystalline phases, observed to co-exist with quasicrystals. The known structure of these phases is shown to be the starting point of building a quasicrystal model in terms of constitutive polyatomic clusters of icosahedral symmetry. It requires to apply inflation properties of quasiperiodicity, and decoration of elementary building tiles. One example is detailed and discussed, in terms of a two-cluster model, in the case of AlLiCu. 相似文献
48.
Qiong-Gui Lin Xin-Jian Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):235-241
We study the influence of a contact (or delta) potential
on the Aharonov-Bohm scattering of nonrelativistic particles. In
general the contact potential has no effect on the scattering as
expected. However, when the magnetic flux and the strength of the
contact potential take some special values, the Aharonov-Bohm
scattering cross-section is manifestly changed. It is shown that
these special values correspond to the simultaneous existence of two
half-bound states in two adjacent angular momentum channels. Two
limiting processes are presented to deal with the singularity of the
contact potential and results of the same nature are obtained. 相似文献
49.
G. De Chiara A. Łoziński G. M. Palma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):179-183
The evolution of a two level system with a slowly varying Hamiltonian, modeled as a spin 1/2 in a slowly varying magnetic
field, and interacting with a quantum environment, modeled as a bath of harmonic oscillators is analyzed using a quantum Langevin
approach. This allows to easily obtain the dissipation time and the correction to the Berry phase in the case of an adiabatic
cyclic evolution. 相似文献
50.
《Comptes Rendus Physique》2016,17(8):808-835
We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect can be characterized by a renormalized light frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled with an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing one to engineer the Jaynes–Cummings lattice and Rabi lattice models through the presence of superconducting qubits in the cavities. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott–superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin–orbit couplings have been successfully implemented in quantum materials and with ultra-cold atoms in optical lattices — using time-dependent Floquet perturbations periodic in time, for example — as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose–Hubbard models in ladder and two-dimensional geometries, producing phase coherence and Meissner currents. The Bose–Hubbard model is related to the Jaynes–Cummings lattice model in the large detuning limit between light and matter (the superconducting qubits). In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase. 相似文献