Electron polarization function and plasmons in metallic armchair graphene nanoribbons

We calculate the polarization function of Dirac fermions in metallic armchair graphene nanoribbons for an arbitrary temperature and doping. We find that at finite temperatures due to the phase space redistribution among inter-band and intra-band electronic transitions in the conduction and valence bands, the full polarization function becomes independent of the temperature and the position of the chemical potential. As a result, for a given width of nanoribbons there exists a single plasmon mode, with the energy dispersion determined by the graphene's fine structure constant. In Coulomb-coupled nanoribbons, this plasmon splits into the basic in-phase and out-of-phase plasmon modes, with the splitting energy determined additionally by the inter-ribbon spacing.Comment: 7 pages, 4 figures; in press in Phys. Rev.

Spin current generation from Coulomb-Rashba interaction in semiconductor bilayers

Electrons in double-layer semiconductor heterostructures experience a special type of spin-orbit interaction which arises in each layer from the perpendicular component of the Coulomb electric field created by electron density fluctuations in the other layer. We show that this interaction, acting in combination with the usual spin-orbit interaction, can generate a spin current in one layer when a charge current is driven in the other. This effect is symmetry-wise distinct from the spin Hall drag. The spin current is not, in general, perpendicular to the drive current.Comment: 4 pages, 2 figure

Beating of Friedel oscillations induced by spin-orbit interaction

By exploiting our recently derived exact formula for the Lindhard polarization function in the presence of Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit interaction (SOI), we show that the interplay of different SOI mechanisms induces highly anisotropic modifications of the static dielectric function. We find that under certain circumstances the polarization function exhibits doubly-singular behavior, which leads to an intriguing novel phenomenon, beating of Friedel oscillations. This effect is a general feature of systems with BR+D SOI and should be observed in structures with a sufficiently strong SOI.Comment: 3 figure

Spin-orbit interaction induced singularity of the charge density relaxation propagator

The charge density relaxation propagator of a two dimensional electron system, which is the slope of the imaginary part of the polarization function, exhibits singularities for bosonic momenta having the order of the spin-orbit momentum and depending on the momentum orientation. We have provided an intuitive understanding for this non-analytic behavior in terms of the inter chirality subband electronic transitions, induced by the combined action of Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit coupling. It is shown that the regular behavior of the relaxation propagator is recovered in the presence of only one BR or D spin-orbit field or for spin-orbit interaction with equal BR and D coupling strengths. This creates a new possibility to influence carrier relaxation properties by means of an applied electric field.Comment: 4 figure

Sub-threshold resonances in few-neutron systems

Three- and four-neutron systems are studied within the framework of the hyperspherical approach with a local S-wave nn-potential. Possible bound and resonant states of these systems are sought as zeros of three- and four-body Jost functions in the complex momentum plane. It is found that zeros closest to the origin correspond to sub-threshold (nnn) (1/2-) and (nnnn) (0+) resonant states. The positions of these zeros turned out to be sensitive to the choice of the $nn$--potential. For the Malfliet- Tjon potential they are E(nnn)=-4.9-i6.9 (MeV) and E(nnnn)=-2.6-i9.0 (MeV). Movement of the zeros with an artificial increase of the potential strength also shows an extreme sensitivity to the choice of potential. Thus, to generate ^3n and ^4n bound states, the Yukawa potential needs to be multiplied by 2.67 and 2.32 respectively, while for the Malfliet-Tjon potential the required multiplicative factors are 4.04 and 3.59.Comment: Latex, 22 pages, no PS-figures, submitted to J.Phys.

Spin Hall Drag

We predict a new effect in electronic bilayers: the {\it Spin Hall Drag}. The effect consists in the generation of spin accumulation across one layer by an electric current along the other layer. It arises from the combined action of spin-orbit and Coulomb interactions. Our theoretical analysis, based on the Boltzmann equation formalism, identifies two main contributions to the spin Hall drag resistivity: the side-jump contribution, which dominates at low temperature, going as $T^2$, and the skew-scattering contribution, which is proportional to $T^3$. The induced spin accumulation is large enough to be detected in optical rotation experiments.Comment: 5 pages, 2 figure

Spin accumulation from interlayer scattering in semiconductor bilayers

http://arxiv.org/PS_cache/arxiv/pdf/1102/1102.1415v1.pdfElectrons in double-layer semiconductor heterostructures experience two types of spin- orbit interaction: one arises within each layer from the lack of bulk inversion symmetry and/or externally applied electric fields; the other arises from the electric field created by electron density fluctuations in the other layer. We show how these two interactions, acting in a concerted manner, produce spin accumulation in one layer when a current is driven in the other. This accumulation has the same temperature dependence (~T^2) as the recently described spin Hall drag accumulation, but it is parametrically stronger in the clean limit.M.M.G. and M.A.S. are grateful to RFBR and \Dynasty" Foundation|ICFPM for nancial support. S.M.B. acknowledges support from EU Grant PIIF-GA-2009-235394, the DFG SFB 689, and the Belgium Science Policy (IAP). G.V. acknowledges support from NSF Grant No. DMR-0705460

Beating of Friedel oscillations induced by spin-orbit interaction

URL:http://link.aps.org/doi/10.1103/PhysRevB.81.205314 DOI:10.1103/PhysRevB.81.205314By exploiting our recently derived exact formula for the Lindhard polarization function in the presence of Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit interaction (SOI), we show that the interplay of different SOI mechanisms induces highly anisotropic modifications of the static dielectric function. We find that under certain circumstances the polarization function exhibits doubly singular behavior. It leads to an intriguing phenomenon, beating of Friedel oscillations, which can be controlled by external fields. This effect is a general feature of systems with BR+D SOI and should be observed in structures with a sufficiently strong SOI.We acknowledge support from EU Grant No. PIIF-GA-2009-235394 S.M.B. , SFB Grant No. 689, and NSF Grant No. DMR-0705460 G.V.

Compact and Loosely Bound Structures in Light Nuclei

A role of different components in the wave function of the weakly bound light nuclei states was studied within the framework of the cluster model, taking into account of orbitals "polarization". It was shown that a limited number of structures associated with the different modes of nucleon motion can be of great importance for such systems. Examples of simple and quite flexible trial wave functions are given for the nuclei $^8$Be, $^6$He. Expressions for the microscopic wave functions of these nuclei were found and used for the calculation of basic nuclear characteristics, using well known central-exchange nucleon-nucleon potentials.Comment: 19 pages, 3 ps figure