Search results for "Valence"

Pairing-excitation versus intruder states inNi68andZr90

2010

A discussion on the nature of the 0{sup +} states in {sup 68}Ni (Z=28, N=40) is presented and a comparison is made with its valence counterpart {sup 90}Zr (Z=40, N=50). Evidence is given for a 0{sup +} proton-intruder state at only {approx}2.2-MeV excitation energy in {sup 68}Ni, while the analogous neutron-intruder states in {sup 90}Zr reside at 4126 and 5441 keV. The application of a shell-model description of 0{sup +} intruder states reveals that many pair-scattered neutrons across N=40 have to be involved to explain the low excitation energy of the proton-intruder configuration in {sup 68}Ni.

Sodium atoms and clusters on graphite by density functional theory

2004

Sodium atoms and clusters $(Nl~5)$ on graphite (0001) are studied using density functional theory, pseudopotentials and periodic boundary conditions. A single Na atom is observed to bind at a hollow site 2.45 \AA{} above the surface with an adsorption energy of 0.51 eV. The small diffusion barrier of 0.06 eV indicates a flat potential energy surface. Increased Na coverage results in a weak adsorbate-substrate interaction, which is evident in the larger separation from the surface in the cases of ${\mathrm{Na}}_{3},$ ${\mathrm{Na}}_{4},$ ${\mathrm{Na}}_{5},$ and the $(2\ifmmode\times\else\texttimes\fi{}2)$ Na overlayer. The binding is weak for ${\mathrm{Na}}_{2},$ which has a full valence el…

Band structure tuning of Heusler compounds: Spin- and momentum-resolved electronic structure analysis of compounds with different band filling

2019

Physical review / B 103(5), 054407 (2021). doi:10.1103/PhysRevB.103.054407

Fingerprints of spin-orbital polarons and of their disorder in the photoemission spectra of doped Mott insulators with orbital degeneracy

2017

We explore the effects of disordered charged defects on the electronic excitations observed in the photoemission spectra of doped transition metal oxides in the Mott insulating regime by the example of the $R_{1-x}$Ca$_x$VO$_3$ perovskites, where $R=$La,$\dots$,Lu. A fundamental characteristic of these vanadium $d^2$ compounds with partly filled $t_{2g}$ valence orbitals is the persistence of spin and orbital order up to high doping, in contrast to the loss of magnetic order in high-$T_c$ cuprates at low defect concentration. We demonstrate that the disordered electronic structure of doped Mott-Hubbard insulators can be obtained with high precision within the unrestricted Hartree-Fock appro…

Minimum instances of topological matter in an optical plaquette

2007

We propose experimental schemes to create and probe minimum forms of different topologically ordered states in a plaquette of an optical lattice: Resonating Valence Bond, Laughlin and string-net condensed states. We show how to create anyonic excitations on top of these liquids and detect their fractional statistics. In addition, we propose a way to design a plaquette ring-exchange interaction, the building block Hamiltonian of a lattice topological theory. Our preparation and detection schemes combine different techniques already demonstrated in experiments with atoms in optical superlattices.

Tailoring the electronic structure of half-metallic Heusler alloys

2009

We investigated element-specific magnetic moments and the spin-resolved unoccupied density of states (DOS) of polycrystalline ${\text{Co}}_{2}\text{Ti}Z$ $(Z=\text{Si},\text{ }\text{Ge},\text{ }\text{Sn},\text{ }\text{Sb})$, ${\text{Co}}_{2}{\text{Mn}}_{x}{\text{Ti}}_{1\ensuremath{-}x}\text{Si}$ and ${\text{Co}}_{2}{\text{MnGa}}_{1\ensuremath{-}x}{\text{Ge}}_{x}$ Heusler alloys using circular dichroism in x-ray absorption spectroscopy (XMCD). We find a small $(l0.03{\ensuremath{\mu}}_{B})$ Ti moment oriented antiparallel and a large $(g3{\ensuremath{\mu}}_{B})$ Mn moment oriented parallel to the Co moment of approximately $1{\ensuremath{\mu}}_{B}$ per atom in the investigated compounds. Orb…

Can the Double Exchange Cause Antiferromagnetic Spin Alignment?

2020

The effect of the double exchange in a square-planar mixed-valence dn+1&minus

Three physical quantum manifolds from the conformal group

1987

A study of coupled-reaction channel effects in the36S +37Cl system, hybridization between single particle orbits

1996

Elastic and inelastic scattering as well as transfer transitions involving a valence proton in thesd- andfp- shell orbits are studied in the interaction of37Cl +36S at ECM=50 MeV. Experimental angular distributions of single particle states of37Cl (elastic and inelastic transfer) are presented with a CRC analysis. In the CRC calculations the effects of inelastic and transfer couplings are studied using known spectroscopic information. In the CRC analysis six single particle bound states and the collective 2+ excitation of36S are included in the coupling scheme. Higher order coupling effects are found to be important. A distinct effect, the mixing of single particle states (of different pari…

Localization vs. Delocalization in Molecules and Clusters: Electronic and Vibronic Interactions in Mixed Valence Systems

1996

The interplay between electron delocalization and magnetic interactions play a key role in areas as diverse as solid state chemistry (bulk magnetic materials, superconductors,...) [1] and biology (iron-sulfur proteins, manganese-oxo clusters ...) [2]. In molecular inorganic chemistry these two electronic processes have been traditionally studied independently. Thus, the electron dynamics has been extensively investigated in mixedvalence dimers [3] as exemplified by the Creutz-Taube complex [(NH3)5RuII(pyrazine)RuIII(NH3)5]. In this kind of molecular complexes one extra electron is delocalized over two diamagnetic metal sites. Therefore, they constitute model systems for the study of the ele…