Hari P. Dahal

Incommensurate spin resonance in URu2Si2

We propose to search for the spin resonance in URu{sub 2}Si{sub 2} at {omega}{sub res} = 4-6meV at the incommensurate wavector Q* = (1 {+-} 0.4, 0, 0). We expect that this spin resonance will set in at temperatures below HO transition and the intensity of this peak will scale as {approx} {Delta}{sub HO} {approx} (T{sub HO} - T). The resonance peak is know to occur in the states with superconducting gap and results in the gapping of the electronic spectrum add ref on SrruO and cel 15. In the case of HO the gap {Delta}{sub HO} results in the partially gapped electron spectrum. That appears to be a sufficient condition, as shown by Wiebe et al to produce a gap in spin excitation spectrum. In addition, we predict a peak in the spin excitation spectrum, as spectral weight redistribution produces the resonance feature. To the best of our knowledge, if the predicted resonance peak indeed occurs, it would be the first case where the spin resonance occurs at an incommensurate vector Q*.

Absence of Wigner crystallization in graphene

Graphene, a single sheet of graphite, has attracted tremendous attention due to recent experiments which demonstrate that carriers in it are described by massless fermions with linear dispersion. In this Brief Report, we consider the possibility of Wigner crystallization in graphene in the absence of an external magnetic field. We show that the ratio of potential and kinetic energy is independent of the carrier density, the tuning parameter that usually drives Wigner crystallization, and find that for given material parameters (dielectric constant and Fermi velocity), Wigner crystallization is not possible. We comment on how these results change in the presence of a strong external magnetic field.

Tuning impurity states in bilayer graphene

We study the impurity states in bilayer graphene in the unitary limit using Greens function method. Unlike in single layer graphene, the presence of impurities at two nonequivalent sites in bilayer graphene produces different impurity states, which is understood as the change in the band structure due to interlayer hopping of electrons. The impurity states can also be tuned by changing the band structure of bilayer grahene through external electric-field bias.

Local impurity effects in superconducting graphene

We study the effect of impurities in superconducting graphene and discuss their influence on the local electronic properties. In particular, we consider the case of magnetic and non-magnetic impurities being either strongly localized or acting as a potential averaged over one unit cell. The spin dependent local density of states is calculated and possibilities for visualizing impurities by means of scanning tunneling experiments is pointed out. A possibility of identifying magnetic scatters even by non spin-polarized scanning tunneling spectroscopy is explained.

Impurity-assisted nanoscale localization of plasmonic excitations in graphene

The plasmon modes of pristine and impurity doped graphene are calculated, using a real-space theory which determines the non-local dielectric response within the random phase approximation. A full diagonalization of the polarization operator is performed, allowing the extraction of all its poles. It is demonstrated how impurities induce the formation of localized modes which are absent in pristine graphene. The dependence of the spatial modulations over few lattice sites and frequencies of the localized plasmons on the electronic filling and impurity strength is discussed. Furthermore, it is shown that the chemical potential and impurity strength can be tuned to control target features of the localized modes. These predictions can be tested by scanning tunneling microscopy experiments.

Pairing symmetry signatures of T 1 in superconducting ferromagnets

We study the nuclear relaxation rate

Visualization of nano-plasmons in graphene

1∕{T}_{1}

Edge states in a honeycomb lattice: Effects of anisotropic hopping and mixed edges

as a function of temperature for a superconducting ferromagnetic coexistent system using a

Spin waves in quasiequilibrium spin systems.

p

Physical properties of ferromagnetic-superconducting coexistent system from a mean-field model

-wave triplet model for the superconducting pairing symmetry. This calculation is contrasted with a singlet