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$_3$ (SVO) bulk single crystals, and La$_{1-x}$Sr$_x$FeO$_3$ (LSFO) and La$_{1-x}$Sr$_x$MnO$_3$ (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

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

The Coupled Modified Korteweg-de Vries Equations

Generalization of the modified KdV equation to a multi-component system, that is expressed by $(\partial u_i)/(\partial t) + 6 (\sum_{j,k=0}^{M-1} C_{jk} u_j u_k) (\partial u_i)/(\partial x) + (\partial^3 u_{i})/(\partial x^3) = 0, i=0, 1, ..., M-1$, 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

Partition Function for a 1-D delta-function Bose Gas

The N-particle partition function of a one-dimensional $\delta$-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

Exactly solvable Wadati potentials in the PT-symmetric Gross-Pitaevskii equation

This note examines Gross-Pitaevskii equations with PT-symmetric potentials of the Wadati type: $V=-W^2+iW_x$. We formulate a recipe for the construction of Wadati potentials supporting exact localised solutions. The general procedure is exemplified by equations with attractive and repulsive cubic nonlinearity bearing a variety of bright and dark solitons.Comment: To appear in Proceedings of the 15 Conference on Pseudo-Hermitian Hamiltonians in Quantum Physics, May 18-23 2015, Palermo, Italy (Springer Proceedings in Physics, 2016

Gradual Disappearance of the Fermi Surface near the Metal-Insulator Transition in La1−x_{1-x}Srx_{x}MnO3_{3}

We report the first observation of changes in the electronic structure of La$_{1-x}$Sr$_{x}$MnO$_{3}$ (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 ($E_{F}$) to the lower Hubbard band, whereas a pseudogap behavior also exists in the ARPES spectra in the close vicinity of $E_{F}$ 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

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