494 research outputs found
Angle-resolved photoemission spectroscopy of perovskite-type transition-metal oxides and their analyses using tight-binding band structure
Nowadays it has become feasible to perform angle-resolved photoemission
spectroscopy (ARPES) measurements of transition-metal oxides with
three-dimensional perovskite structures owing to the availability of
high-quality single crystals of bulk and epitaxial thin films. In this article,
we review recent experimental results and interpretation of ARPES data using
empirical tight-binding band-structure calculations. Results are presented for
SrVO (SVO) bulk single crystals, and LaSrFeO (LSFO) and
LaSrMnO (LSMO) thin films. In the case of SVO, from comparison
of the experimental results with calculated surface electronic structure, we
concluded that the obtained band dispersions reflect the bulk electronic
structure. The experimental band structures of LSFO and LSMO were analyzed
assuming the G-type antiferromagnetic state and the ferromagnetic state,
respectively. We also demonstrated that the intrinsic uncertainty of the
electron momentum perpendicular to the crystal surface is important for the
interpretation of the ARPES results of three-dimensional materials.Comment: 25 pages, 12 figure
The Coupled Modified Korteweg-de Vries Equations
Generalization of the modified KdV equation to a multi-component system, that
is expressed by , is studied. We apply a new extended version of the inverse
scattering method to this system. It is shown that this system has an infinite
number of conservation laws and multi-soliton solutions. Further, the initial
value problem of the model is solved.Comment: 26 pages, LaTex209 file, uses jpsj.st
Graphical representation of the partition function for a 1-D delta-function Bose gas
One-dimensional repulsive delta-function bose system is studied. By only
using the Bethe ansatz equation, n-particle partition functions are exactly
calculated. From this expression for the n-particle partition function, the
n-particle cluster integral is derived. The results completely agree with those
of the thermal Bethe ansatz (TBA). This directly proves the validity of the
TBA. The theory of partitions and graphs is used to simplify the discussion.Comment: 15 page
Madelung potentials and covalency effect in strained LaSrMnO thin films studied by core-level photoemission spectroscopy
We have investigated the shifts of the core-level photoemission spectra of
LaSrMnO thin films grown on three kinds of substrates,
SrTiO, (LaAlO)-(SrAlTaO), and
LaAlO. The experimental shifts of the La 4d and Sr 3d core levels are
almost the same as the calculation, which we attribute to the absence of
covalency effects on the Madelung potentials at these atomic sites due to the
nearly ionic character of these atoms. On the other hand, the experimental
shifts of the O and Mn core levels are negligibly small, in
disagreement with the calculation. We consider that this is due to the strong
covalent character of the Mn-O bonds.Comment: 4 pages, 5 figure
In-situ photoemission study of Pr_{1-x}Ca_xMnO_3 epitaxial thin films with suppressed charge fluctuations
We have performed an {\it in-situ} photoemission study of Pr_{1-x}Ca_xMnO_3
(PCMO) thin films grown on LaAlO_3 (001) substrates and observed the effect of
epitaxial strain on the electronic structure. We found that the chemical
potential shifted monotonically with doping, unlike bulk PCMO, implying the
disappearance of incommensurate charge fluctuations of bulk PCMO. In the
valence-band spectra, we found a doping-induced energy shift toward the Fermi
level (E_F) but there was no spectral weight transfer, which was observed in
bulk PCMO. The gap at E_F was clearly seen in the experimental band dispersions
determined by angle-resolved photoemission spectroscopy and could not be
explained by the metallic band structure of the C-type antiferromagnetic state,
probably due to localization of electrons along the ferromagnetic chain
direction or due to another type of spin-orbital ordering.Comment: 5 pages, 4 figure
Partition Function for a 1-D delta-function Bose Gas
The N-particle partition function of a one-dimensional -function bose
gas is calculated explicitly using only the periodic boundary condition (the
Bethe ansatz equation). The N-particles cluster integrals are shown to be the
same as those by the thermal Bethe ansatz method.Comment: 30 page
Gradual Disappearance of the Fermi Surface near the Metal-Insulator Transition in LaSrMnO
We report the first observation of changes in the electronic structure of
LaSrMnO (LSMO) across the filling-control metal-insulator
(MI) transition by means of in situ angle-resolved photoemission spectroscopy
(ARPES) of epitaxial thin films. The Fermi surface gradually disappears near
the MI transition by transferring the spectral weight from the coherent band
near the Fermi level () to the lower Hubbard band, whereas a pseudogap
behavior also exists in the ARPES spectra in the close vicinity of for
the metallic LSMO. These results indicate that the spectral weight transfer
derived from strong electron-electron interaction dominates the gap formation
in LSMO associated with the filling-control MI transition.Comment: 11 pages, 4 figure
Systematic tight-binding analysis of ARPES spectra of transition-metal oxides
We have performed systematic tight-binding (TB) analyses of the
angle-resolved photoemission spectroscopy (ARPES) spectra of transition-metal
(TM) oxides AO ( Ti, V, Mn, and Fe) with the perovskite-type
structure and compared the obtained parameters with those obtained from
configuration-interaction (CI) cluster-model analyses of photoemission spectra.
The values of from ARPES are found to be similar to the
charge-transfer energy from O orbitals to empty TM 3d orbitals
and much larger than (: on-site Coulomb energy) expected for
Mott-Hubbard-type compounds including SrVO. values
from {\it ab initio} band-structure calculations show similar behaviors to
those from ARPES. The values of the transfer integrals to describe the
global electronic structure are found to be similar in all the estimates,
whereas additional narrowing beyond the TB description occurs in the ARPES
spectra of the band.Comment: 5 pages, 3 figure
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