Related papers: Roton-like mode in solid He-4
Quasi-one-dimensional solitons that may occur in an elongated Bose-Einstein condensate become unstable at high particle density. We study two basic modes of instability and the corresponding bifurcations to genuinely three-dimensional…
Surface modes in a Bose-Einstein condensate of sodium atoms have been studied. We observed excitations of standing and rotating quadrupolar and octopolar modes. The modes were excited with high spatial and temporal resolution using the…
In this paper we extend the hydrodynamic results of [1] and study, analytically, the propagation of Bogoliubov phonons on top of Bose-Einstein condensates with step-like discontinuities by taking into account dispersion effects. We focus on…
We investigate electron-phonon coupling in many-electron systems using dynamical mean-field theory in combination with the numerical renormalization group. This non-perturbative method reveals significant precursor effects to the gap…
Radio-frequency compressed ultrafast electron diffraction has been used to probe the coherent and incoherent coupling of impulsive electronic excitation at 1.55 eV (800 nm) to optical and acoustic phonon modes directly from the perspective…
By applying an unrestriced Hartree-Fock approximation and a Random Phase approximation to multiband Peierls-Hubbard Hamiltonians, we determine the phonon mode structure in models of transition metal oxides in the presence of intrinsic…
We theoretically study homogeneously trapped atomic Bose-Einstein condensates where all three momentum components couple to a pseudo-spin-$1/2$ degree of freedom. Tuning the anisotropies of spin-orbit coupling and the spin-dependent…
High harmonic generation (HHG) in solid and gaseous targets has been proven to be a powerful avenue for the generation of attosecond pulses, whereas the influence of electron-phonon scattering on HHG is a critical outstanding problem. Here…
We have measured the room-temperature phonon spectrum of Mo-stabilized $\gamma-$U. The dispersion curves show unusual softening near the H point, q=[1/2,1/2,1/2], which may derive from the metastability of the $\gamma-$U phase or from…
We present a theoretical study of the excitations of the two-dimensional supersolid state of a Bose-Einstein condensate with either dipole-dipole interactions or soft-core interactions. This supersolid state has three gapless excitation…
Investigation of the inelastic neutron scattering spectra in Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ near a signature wave vector $\mathbf{Q} = (1,0,0)$ for the bond-order wave (BOW) formation of parent compound Fe$_{1+y}$Te [Phys. Rev. Lett. 112,…
The influence of collective phonon excitations, due to intersite atomic interactions, on the stability of optical lattices is analyzed. These phonon excitations are shown to essentially reduce the ability of atoms to be localized. The…
Ultrafast carrier and phonon dynamics at the buried heterointerface of GaP/Si(001) are investigated by means of two-color pump-probe reflectivity measurements. The carrier-induced reflectivity signal exhibits a resonant enhancement at…
Nonlinear localized excitations in one-dimensional diatomic lattices with cubic and quartic nonlinearity are considered analytically by a quasi-discreteness approach. The criteria for the occurence of asymmetric gap solitons (with vibrating…
In this paper, we study the spectrum of the Regge poles (RPs), which are the counterparts of quasinormal modes, in a draining bathtub vortex within a two-component Bose-Einstein condensate (BEC) system. We study the gapped excitations of…
Long-lived, spatially localized, and temporally oscillating nonlinear excitations are predicted by numerical simulation of coupled Gross-Pitaevskii equations. These oscillons closely resemble the time-periodic breather solutions of the…
Since the discovery of superfluidity in He4 and Landau's phenomenological theory, the relationship between Bose condensation and superfluidity has been intensely debated. He4 is known by now to be both superfluid and condensed at low…
Development of topological insulating phases in IV-VI compounds under dynamic lattice deformations is studied using first-principles methods. Unlike the static state of topological phases at equilibrium conditions, we show that non-trivial…
We investigate two-dimensional (2D) states of Bose-Einstein condensates (BEC) with self-attraction or self-repulsion, trapped in an axially symmetric optical-lattice potential periodic along the radius. Unlike previously studied 2D models…
Liquid helium and spin-1/2 cold-atom Fermi gases both exhibit in their superfluid phase two distinct types of excitations, gapless phonons and gapped rotons or fermionic pair-breaking excitations. In the long wavelength limit, revising and…