42 research outputs found
Spin-Orbital Liquid on a Triangular Lattice
Using Lanczos exact diagonalization of finite clusters we demonstrate that
the spin-orbital model for triply degenerate orbitals on a
triangular lattice provides an example of a spin-orbital liquid ground state.
We also show that the spin-orbital liquid involves entangled valence bond
states which violate the Goodenough-Kanamori rules, and modify effective spin
exchange constants.Comment: 4 pages, 2 figures, presented at Euroconference Physics of Magnetism
201
Design of the Production Technology of the Inner Square of the Casting
Bakalářská práce pojednává o návrhu technologie opracování čtyřhranného otvoru
v odlitku. V úvodu jsou představeny různé možné technologie vhodné pro zhotovení čtyř-hranného otvoru. Pro vybraný díl byl zvolen optimální technologický postup opracování včetně doporučení vhodných strojů a nástrojů. Následně byl zpracován technologický postup uzpůsobený pro vybranou technologii výroby. V závěru byla provedena analýza výrobních nákladů možných technologií zhotovení čtyřhranného otvoru.Bachelor thesis is about the design proposal of the technology of processing square bore in a cast. In the introduction part different usable technologies for making the bore are introduced. For the chosen part the optimal technological process was chosen including the recommendation of suitable machines and tools. After that the technological process adapted for the used technology is depicted. In the conclusion the analysis of production costs of technologies suitable for making the square bore was conducted.346 - Katedra obrábění, montáže a strojírenské metrologiedobř
The origin of strong correlations and superconductivity in NaCoO
We propose a minimal model resolving a puzzle of enigmatic correlations
observed in sodium-rich NaCoO where one expects a simple, free motion
of the dilute holes doped into a band insulator NaCoO. The model
also predicts singlet superconductivity at experimentally observed
compositions. The model is based on a key property of cobalt oxides -- the
spin-state quasidegeneracy of CoO octahedral complex -- leading to an
unusual physics of, {\it e.g.}, LaCoO. We show that correlated hopping
between and states leads to the spin-polaron physics at , and to an extended s-wave pairing at larger doping when coherent fermionic
bands are formed.Comment: 7 pages, 6 figures, extended version as published in PR
Spin polaron theory for the photoemission spectra of layered cobaltates
Recently, strong reduction of the quasiparticle peaks and pronounced
incoherent structures have been observed in the photoemission spectra of
layered cobaltates. Surprisingly, these many-body effects are found to increase
near the band insulator regime. We explain these unexpected observations in
terms of a novel spin-polaron model for CoO_2 planes which is based on a fact
of the spin-state quasidegeneracy of Co^{3+} ions in oxides. Scattering of the
photoholes on spin-state fluctuations suppresses their coherent motion. The
observed ``peak-dip-hump'' type lineshapes are well reproduced by the theory.Comment: 4 pages, 4 figure