共查询到20条相似文献,搜索用时 15 毫秒
1.
Vogt P De Padova P Quaresima C Avila J Frantzeskakis E Asensio MC Resta A Ealet B Le Lay G 《Physical review letters》2012,108(15):155501
Because of its unique physical properties, graphene, a 2D honeycomb arrangement of carbon atoms, has attracted tremendous attention. Silicene, the graphene equivalent for silicon, could follow this trend, opening new perspectives for applications, especially due to its compatibility with Si-based electronics. Silicene has been theoretically predicted as a buckled honeycomb arrangement of Si atoms and having an electronic dispersion resembling that of relativistic Dirac fermions. Here we provide compelling evidence, from both structural and electronic properties, for the synthesis of epitaxial silicene sheets on a silver (111) substrate, through the combination of scanning tunneling microscopy and angular-resolved photoemission spectroscopy in conjunction with calculations based on density functional theory. 相似文献
2.
Chui ST 《Physical review letters》1987,58(13):1355-1358
3.
We study in detail the transport properties of a model of conducting electrons in the presence of double exchange between localized spins arranged on a 2D Kagome lattice, as introduced by Ohgushi, Murakami and Nagaosa. The relationship between the canting angle of the spin texture θ and the Berry phase field flux per triangular plaquette φ is derived explicitly and we emphasize the similarities between this model and Haldane's honeycomb lattice version of the quantum Hall effect. The quantization of the transverse (Hall) conductivity σ xy is derived explicitly from the Kubo formula and a direct calculation of the longitudinal conductivity σ xx shows the existence of a metal–insulator transition as a function of the canting angle θ (or flux density φ). This transition might be linked to that observable in the manganite compounds or in the pyrochlore ones, as the spin ordering changes from ferromagnetic to canted. 相似文献
4.
Elementary theoretical approaches to the ordering of the mobile ions in the conduction plane of β-alumina and β″ alumina predict a first order phase transition. Such transitions are not seen in experiments. Inhomogeneity and/or two-dimensionality may explain the difference between theory and experiment. 相似文献
5.
Fractional charge may arise when fermionic zero modes exist in a topological background field. In biased bilayer graphene (BBLG), the bias plays the role of the nontrivial background field. When semi-infinite BBLG with a zigzag edge is used, the dynamics induces an odd number of zero-energy modes, which, together with the conjugation symmetry between positive-?and negative-energy states, are the requisite conditions for fractionalization. Exploiting the trigonal interaction to isolate a given zero-energy mode on the zigzag edge, we consider extended and localized modes (the latter being obtained from a localized wavepacket generated by prior irradiation of the sample with an electromagnetic vortex). The valley degeneracy is lifted by a layer asymmetry, while an edge-induced spin polarization breaks the spin degeneracy. We describe scenarios for the detection of charge-[Formula: see text] edge states. 相似文献
6.
Localized axisymmetric inhomogeneous states with a continuous distribution of the director field can exist in nematics. Such
structures are compressed into dense filaments under the influence of a magnetic or electric field. It is hypothesized that
the given states can be achieved in filamentary nematic textures. This model is an alternative to the conventional disclination
model. Two types of lattices of axial structures can exist in the entire range of existence of the modulated state. Axial
structures with a kernel of finite radius can exist in cylindrical capillaries. The structure and equilibrium dimensions of
the axial states are easily altered over a wide range under the influence of an applied field. The feasibility of utilizing
isolated axial structures and lattices of such structures in optical data processing and imaging devices is discussed. The
most promising outlook in this regard is for modulated states and axial structures in chiral liquid crystals exhibiting spontaneous
polarization.
Zh. éksp. Teor. Fiz. 113, 1675–1697 (May 1998) 相似文献
7.
Overlaying commensurate optical lattices with various configurations called superlattices can lead to exotic lattice topologies and, in turn, a discovery of novel physics. In this study, by overlapping the maxima of lattices, a new isolated structure is created, while the interference of minima can generate various “sublattice” patterns. Three different kinds of primitive lattices are used to demonstrate isolated square, triangular, and hexagonal “sublattice” structures in a two-dimensional optical superlattice, the patterns of which can be manipulated dynamically by tuning the polarization, frequency, and intensity of laser beams. In addition, we propose the method of altering the relative phase to adjust the tunneling amplitudes in “sublattices”. Our configurations provide unique opportunities to study particle entanglement in “lattices” formed by intersecting wells and to implement special quantum logic gates in exotic lattice geometries. 相似文献
8.
The influence of the conduction-electron spin magnetization density, induced in a two-dimensional electron layer by a microwave electromagnetic field, on the reflection and transmission of the field is considered. Because of the induced magnetization and electric current, both the electric and magnetic components of the field should have jumps on the layer. A way to match the waves on two sides of the layer, valid when the quasi-two-dimensional electron gas is in the one-mode state, is proposed. By following this way, the amplitudes of transmitted and reflected waves as well as the absorption coefficient are evaluated. 相似文献
9.
Karl-Heinz Ernst 《Frontiers of Physics in China》2010,5(4):340-346
We discuss the occurrence of transition structures observed in molecular self-assembly at surfaces. The increasing surface
coverage transitions from low coverage structures to high coverage structures are a common phenomenon. However, often observed
and not perfectly understood is the formation of intermediate structures, sometimes with lower lateral density than the initial
phase. We will present different examples from our recent work and discuss the possible mechanisms of intermediate phase formation.
In addition, we present intermediate structures occurring due to temperature-controlled reversible phase transitions. 相似文献
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A differential-geometry analysis is employed to investigate the transmission of electrons through a curved quantum-wire structure. Although the problem is a three-dimensional spatial problem, the Schrödinger equation can be separated into three general coordinates. Hence, the proposed method is computationally fast and provides direct (geometrical) parameter insight as regards the determination of the electron transmission coefficient. We present, as a case study, calculations of the electron conductivity of a helically shaped quantum-wire structure and discuss the influence of the quantum-wire centerline radius of curvature and pitch length for the conductivity versus the chemical potential. 相似文献
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One-dimensional metals, such as quantum wires or carbon nanotubes, can carry charge in arbitrary units, smaller or larger than a single electron charge. However, according to Luttinger theory, which describes the low-energy excitations of such systems, when a single electron is injected by tunneling into the middle of such a wire, it will tend to break up into separate charge pulses, moving in opposite directions, which carry definite fractions f and (1-f) of the electron charge, determined by a parameter g that measures the strength of charge interactions in the wire. (The injected electron will also produce a spin excitation, which will travel at a different velocity than the charge excitations.) Observing charge fractionalization physics in an experiment is a challenge in those (nonchiral) low-dimensional systems which are adiabatically coupled to Fermi liquid leads. We theoretically discuss a first important step towards the observation of charge fractionalization in quantum wires based on momentum-resolved tunneling and multi-terminal geometries, and explain the recent experimental results of Steinberg et al. [H. Steinberg, G. Barak, A. Yacoby, L.N. Pfeiffer, K.W. West, B.I. Halperin, K. Le Hur, Nature Physics 4 (2008) 116]. 相似文献
14.
《Nuclear Physics B》1986,269(1):54-76
We develop a new canonical r-s matrix type approach for integrable two-dimensional models of non-ultralocal type. The L-matrices algebra and the monodromy matrices' algebras are given in terms of the usual r-matrix and of the new s-matrix, which, for consistency (Jacobi identity) have to obey an extended, dynamical Yang-Baxter type equation. The possible violation of the Jacobi identity arising in the (naive) equal-point limit of the monodromy matrices' algebras is discussed and a general, consistent procedure, i.e. satisfying the Jacobi identity, is defined. The method is applied to the complex sine-Gordon model. 相似文献
15.
V. M. Rozenbaum 《Journal of Experimental and Theoretical Physics》1997,84(2):368-374
A model of a two-dimensional antiferromagnet with an arbitrary anisotropic interaction that allows for degeneracy of the ground
state is proposed. The lifting of degeneracy by thermodynamic fluctuations and the accompanying effects are studied by a method
of self-consistent calculations of Gaussian angular fluctuations that is asymptotically exact at low temperatures. Fluctuations
are shown to lead to collinear ordering of the orientations of magnetic sublattices, an effect that initiates long-range orientational
order in systems with anisotropic interaction but retains only short-range order in systems with isotropic short-range interaction.
The temperature patterns of the orientational correlators are given for the particular cases of dipole and isotropic short-range
interaction models. The nature of the Ising-like behavior of the system is discussed for the case of a strong anisotropy of
the correlators, which corresponds to quasi-one-dimensional behavior.
Zh. éksp. Teor. Fiz. 111, 669–680 (February 1997) 相似文献
16.
This paper details the study of electron transport through a two-dimensional curved quantum waveguide. The curvature of the quantum waveguide is found to greatly affect the transport properties. It is shown that no evanescent mode exists when the inner radius of the curved part of the waveguide is zero. Also, this paper details how localized modes with energy below the Fermi energy can be formed in the curved part due to curvilinear effects. A series of Fano-resonance type dips of the transmission coefficient appear because of the presence of localized modes. Due to the quantum effect, the transmission coefficient and the traversal time increase nonlinearly with the curved angle θ0. This nonlinear property is destroyed as the radius increases. 相似文献
17.
A. Niang G. Ablart J. Pescia Y. Servant R. Duplessix N. B. Chanh T. Marys S. K. Misra 《Applied magnetic resonance》1995,8(2):319-333
The anisotropies of the EPR linewidth andg-factor were investigated in two-dimensional molecular composites of the type [NH3?R?NH3]MX4. Measurements were performed both in single crystals and powders over the temperature range 4.2–290 K. The spin-lattice relaxation timeT 1 was measured using the modulation method, as a function of temperature. The samples exhibit different structures and coupling interactions, according to the nature of the halogen X, the metal M and the organic radical R. We have analysed the influence of these parameters on spin behavior by studying the samples [NH3?(CH) n ?NH3]MX4 with M=Mn, Cu; X=Cl, Br, andn=2, 3, 4, 5. When R is constituted by molecules with unsaturated bonds, these materials can be considered as excellent matrices for selective polymerisation reactions by irradiation or thermal processing. We have performed EPR measurements on the heated complex of propargylamine and cadmium chloride [HC∈C?CH2?NH3]2CdCl4. The obtained data are interpreted taking into account the strong exchange interaction and the various coupling interactions in the samples. The thermal dependences ofT 1 are explained by means of the Bloembergen and Wang three-reservoir model. The data whow spin diffusion when the metal is manganese, and an antisymmetric exchange interaction modulated by phonons in the case of copper. The nature of the halogen plays an important role in spin dynamics and namely in spin-lattice relaxation. The results obtained on [HC∈C?CH2?NH3]2CdCl4 after heating under vaccum show the creation of many paramagnetic centers due to the vanishing of triple bonds and the occurrence of a strong exchange interaction. 相似文献
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19.
In this work we briefly review the present day perspectives for exploiting conventional non-magnetic semiconductor nano-technology to design high speed spin-filter devices. In recent theoretical investigations a high spin polarization has been predicted for the ballistic tunneling current in semiconductor single- and double-barrier asymmetric tunnel structures of III–V semiconductors with strong Rashba spin–orbit coupling. We show in this paper that the polarization in the tunneling can probability be sufficiently increased for producing realistic single-barrier structures by including of the Dresselhaus term into consideration. 相似文献
20.
K. A. Nasyrov S. S. Shaĭmeev V. A. Gritsenko J. H. Han C. W. Kim J. -W. Lee 《Journal of Experimental and Theoretical Physics》2006,102(5):810-820
The kinetics of electron and hole accumulation in metal-oxide-nitride-oxide-semiconductor structures is studied. Experimental data are compared with a theoretical model that takes into account tunnel injection, electron and hole capture by traps in amorphous silicon nitride SiNx, and trap ionization. Agreement between experimental and calculated data is obtained for the bandgap width E g = 8.0 eV of amorphous SiO2, which corresponds to the barrier for holes Φh = 3.8 eV at the Si/SiO2 interface. The tunneling effective masses for holes in SiO2 and SiNx are estimated at m h * ≈ (0.4–0.5)m 0. The parameters of electron and hole traps in SiNx are determined within the phonon-coupled trap model: the optical energy W opt = 2.6 eV and the thermal energy W T = 1.3 eV. 相似文献