Search results for "electrons"
showing 10 items of 1325 documents
Electron Fabry-Perot interferometer with two entangled magnetic impurities
2007
We consider a one-dimensional (1D) wire along which single conduction electrons can propagate in the presence of two spin-1/2 magnetic impurities. The electron may be scattered by each impurity via a contact-exchange interaction and thus a spin-flip generally occurs at each scattering event. Adopting a quantum waveguide theory approach, we derive the stationary states of the system at all orders in the electron-impurity exchange coupling constant. This allows us to investigate electron transmission for arbitrary initial states of the two impurity spins. We show that for suitable electron wave vectors, the triplet and singlet maximally entangled spin states of the impurities can respectively…
A many-body approach to transport in quantum systems : From the transient regime to the stationary state
2022
We review one of the most versatile theoretical approaches to the study of time-dependent correlated quantum transport in nano-systems: the non-equilibrium Green's function (NEGF) formalism. Within this formalism, one can treat, on the same footing, inter-particle interactions, external drives and/or perturbations, and coupling to baths with a (piece-wise) continuum set of degrees of freedom. After a historical overview on the theory of transport in quantum systems, we present a modern introduction of the NEGF approach to quantum transport. We discuss the inclusion of inter-particle interactions using diagrammatic techniques, and the use of the so-called embedding and inbedding techniques w…
Determination of the electron-detachment energies of 2'-deoxyguanosine 5'-monophosphate anion: influence of the conformation.
2009
The vertical electron-detachment energies (VDEs) of the singly charged 2'-deoxyguanosine 5'-monophosphate anion (dGMP - ) are determined by using the multiconfigurational second-order perturbation CASPT2 method at the MP2 ground-state equilibrium geometry of relevant conformers. The origin of the unique low-energy band in the gas phase photoelectron spectrum of dGMP - , with maximum at around 5.05 eV, is unambiguously assigned to electron detachment from the highest occupied molecular orbital of π-character belonging to guanine fragment of a syn conformation. The presence of a short H-bond linking the 2-amino and phosphate groups, the guanine moiety acting as proton donor, is precisely resp…
Valence Topological Charge-Transfer Indices for Reflecting Polarity: Correction for Heteromolecules
2005
Valence topological charge-transfer (CT) indices are applied to the calculation of dipole moments mu. The mu calculated by algebraic and vector semisums of the CT indices are defined. The model is generalized for molecules with heteroatoms and corrected for sp(3)-heteromolecules. The ability of the indices for the description of the molecular charge distribution is established by comparing them with mu of the valence-isoelectronic series of cyclopentadiene, benzene and styrene. Two CT indices, mu(vec) (vector semisum of vertex-pair mu) and mu(vec)V (valence mu(vec)) are proposed. The mu(vec) behaviour is intermediate between mu(vec) and mu(experiment). The correction is produced in the corr…
Magnetoelectric Cavity Magnonics in Skyrmion Crystals
2022
We present a theory of magnetoelectric magnon-photon coupling in cavities hosting noncentrosymmetric magnets. Analogously to nonreciprocal phenomena in multiferroics, the magnetoelectric coupling is time-reversal and inversion asymmetric. This asymmetry establishes a means for exceptional tunability of magnon-photon coupling, which can be switched on and off by reversing the magnetization direction. Taking the multiferroic skyrmion-host Cu$_2$OSeO$_3$ with ultralow magnetic damping as an example, we reveal the electrical activity of skyrmion eigenmodes and propose it for magnon-photon splitting of ``magnetically dark'' elliptic modes. Furthermore, we predict a cavity-induced magnon-magnon c…
Electron-hole bilayer quantum dots: Phase diagram and exciton localization
2003
We studied a vertical ``quantum dot molecule'', where one of the dots is occupied with electrons and the other with holes. We find that different phases occur in the ground state, depending on the carrier density and the interdot distance. When the system is dominated by shell structure, orbital degeneracies can be removed either by Hund's rule, or by Jahn-Teller deformation. Both mechanisms can lead to a maximum of the addition energy at mid-shell. At low densities and large interdot distances, bound electron-hole pairs are formed.
The resonant state at filling factor �� = 1/2 in chiral fermionic ladders
2017
Helical liquids have been experimentally detected in both nanowires and ultracold atomic chains as the result of strong spin-orbit interactions. In both cases the inner degrees of freedom can be considered as an additional space dimension, providing an interpretation of these systems as synthetic ladders, with artificial magnetic fluxes determined by the spin-orbit terms. In this work, we characterize the helical state which appears at filling $��=1/2$: this state is generated by a gap arising in the spin sector of the corresponding Luttinger liquid and it can be interpreted as the one-dimensional (1D) limit of a fractional quantum Hall state of bosonic pairs of fermions. We study its main …
Detecting topology through dynamics in interacting fermionic wires
2020
We describe a protocol to read out the topological invariant of interacting 1D chiral models, based on measuring the mean chiral displacement of time-evolving bulk excitations. We present analytical calculations and numerical Matrix Product State simulations of interacting Su-Schrieffer-Heeger (SSH) chains, demonstrating how the mean chiral displacement allows to distinguish between topological insulator, trivial insulator and symmetry-broken phases. Finally, we provide an experimental blueprint for realizing a model displaying these three phases and describe how to detect those.
Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field
2011
We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work is motivated by recent experiments on the compound (C5H12N)2CuBr4 (BPCB). We use a combination of numerical and analytical methods, in particular the density matrix renormalization group (DMRG) technique, to explore the phase diagram and the excitation spectra of such a system. We give detailed results on the temperature dependence of the magnetization and the specific heat, and the magnetic field dependence of the nuclear magnetic resonance (NMR) relaxation rate of single ladders. For coupled ladders, treating the weak interladder coupling within a mean-field or quantum Monte Carlo approach, we compute the transit…
Effect of water on glass transition in starch/sucrose matrices investigated through positron annihilation lifetime spectroscopy: a new approach
2011
Glass transition is studied through positron annihilation lifetime spectroscopy (PALS) in maize starch matrices containing 10 (batch STS10) and 20 (STS20) w/w% sucrose, as a function of temperature (T) and water content (c(w)). To circumvent important losses of water upon heating while recording the PALS spectra, a new method is developed: instead of a series of measurements of τ(3), the triplet positronium lifetime, at different T, the latter is kept constant and the series relates to c(w), which is left to decrease at a constant rate. Similarly to the changes in τ(3) with T, the τ(3)vs. c(w) plots obtained show a smooth linear increase until a break, denoting the occurrence of glass trans…