Search results for "quasiparticle"
showing 10 items of 280 documents
The peculiarities of the phase diagram of heavy fermion metal CeCoIn5
2007
We analyze the low temperature experimental magnetic field–temperature H–T phase diagram of CeCoIn5. We demonstrate that its main features can be well explained within Landau quasiparticle picture incorporating the fact that quasiparticles form so-called fermion-condensate (FC) state emerging behind the fermion condensation quantum phase transition (FCQPT). We show that near FCQPT, the fluctuations are strongly suppressed while FC by itself is “protected” from above fluctuations by the first order phase transition. We demonstrate that the electronic system of CeCoIn5 can be shifted from the ordered towards disordered side of FCQPT by the application of magnetic field therefore giving a uniq…
Dynamically screened vertex correction to $GW$
2020
Diagrammatic perturbation theory is a powerful tool for the investigation of interacting many-body systems, the self-energy operator $\mathrm{\ensuremath{\Sigma}}$ encoding all the variety of scattering processes. In the simplest scenario of correlated electrons described by the $GW$ approximation for the electron self-energy, a particle transfers a part of its energy to neutral excitations. Higher-order (in screened Coulomb interaction $W$) self-energy diagrams lead to improved electron spectral functions (SFs) by taking more complicated scattering channels into account and by adding corrections to lower order self-energy terms. However, they also may lead to unphysical negative spectral f…
Evolution from γ -soft to stable triaxiality in Nd136 as a prerequisite of chirality
2018
The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well underst…
AN OPTICAL PLAQUETTE: MINIMUM EXPRESSIONS OF TOPOLOGICAL MATTER
2009
Topological matter is an unconventional form of matter: it exhibits a global hidden order which is not associated with the spontaneous breaking of any symmetry. The defects of this exotic type of order are anyons, quasiparticles with fractional statistics. Moreover, when living on a surface with non-trivial topology, like a plane with a hole or a torus, this type of matter develops a number of degenerate states which are locally indistinguishable and could be used to build a quantum memory naturally resistant to errors. Except for the fractional quantum Hall effect there is no experimental evidence as to the existence of topologically ordered phases, and it remains a huge challenge to devel…
Route towards Dirac and Weyl antiferromagnetic spintronics
2017
Topological quantum matter and spintronics research have been developed to a large extent independently. In this Review we discuss a new role that the antiferromagnetic order has taken in combining topological matter and spintronics. This occurs due to the complex microscopic symmetries present in antiferromagnets that allow, e.g., for topological relativistic quasiparticles and the newly discovered N\'{e}el spin-orbit torques to coexist. We first introduce the concepts of topological semimetals and spin-orbitronics. Secondly, we explain the antiferromagnetic symmetries on a minimal Dirac semimetal model and the guiding role of $\textit{ab initio}$ calculations in predictions of examples of…
Examination of the influence of transfer channels on the barrier height distribution: Scattering ofNe20onNi58,Ni60, andNi61at near-barrier energies
2016
Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations.Purpose: The study of the barrier height distributions for the $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{58,60,61}\mathrm{Ni}$ systems requires information on transfer cross sections at near-barrier energies.Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and $\mathrm{\ensuremath{\Delta}}E\text{\ens…
Fourth-order perturbation theory for the half-filled Hubbard model in infinite dimensions
2003
We calculate the zero-temperature self-energy to fourth-order perturbation theory in the Hubbard interaction $U$ for the half-filled Hubbard model in infinite dimensions. For the Bethe lattice with bare bandwidth $W$, we compare our perturbative results for the self-energy, the single-particle density of states, and the momentum distribution to those from approximate analytical and numerical studies of the model. Results for the density of states from perturbation theory at $U/W=0.4$ agree very well with those from the Dynamical Mean-Field Theory treated with the Fixed-Energy Exact Diagonalization and with the Dynamical Density-Matrix Renormalization Group. In contrast, our results reveal t…
Shot noise for resonant Cooper pair tunneling
2001
We study intrinsic noise of current in a superconducting single-electron transistor, taking into account both coherence effects and Coulomb interaction near a Cooper-pair resonance. Due to this interplay, the statistics of tunneling events deviates from the Poisson distribution and, more important, it shows even-odd asymmetry in the transmitted charge. The zero-frequency noise is suppressed significantly when the quasiparticle tunneling rates are comparable to the coherent oscillation frequency of Cooper pairs.
Direct observation of the quasiparticle relaxation in YBa2Cu3O7
1999
Abstract The real and imaginary parts of the optical conductivity ( σ 1 + iσ 2 ) in the superconducting state of YBa 2 Cu 3 O 7−δ thin films have been obtained by submillimeter spectroscopy for frequencies from 3 to 35 cm −1 . The quasiparticle relaxation can be directly observed in this frequency range. A Drude-type analysis allows to extract the temperature dependence of the scattering rate. The collapse of the relaxation rates provides clear experimental evidence that the spin fluctuations become gapped below T C .
Flux-flow instability and its anisotropy inBi2Sr2CaCu2O8+δsuperconducting films
1999
We report measurements on voltage instability at high flux-flow velocities in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ superconducting films. Current-voltage $(I\ensuremath{-}V)$ characteristics have been measured as a function of temperature, magnetic field, and angle between the field and the c axis of the sample. Voltage jumps were observed in $I\ensuremath{-}V$ characteristics taken in all magnetic-field directions and in extended temperature and field ranges. An analysis of the experimental data, based on a theory for viscous flux-flow instability with a finite heat-removal rate from the sample, yielded the inelastic scatterin…