arXiv subjects

Masuo Suzuki

Publications and source records attributed to Masuo Suzuki.

23 records · Page 2Linked to original sources

arXiv1998

Symmetry Properties on Magnetization in the Hubbard Model at Finite Temperatures

By making use of some symmetry properties of the relevant Hamiltonian, two fundamental relations between the ferromagnetic magnetization and a spin correlation function are derived for the $d (=1,2,3)$-dimensional Hubbard model at finite temperatures. These can be viewed as a kind of Ward-Takahashi identities. The properties of the magnetization as a function of the applied field are discussed. The results thus obtained hold true for both repulsive and attractive on-site Coulomb interactions, and for arbitrary electron fillings.

cond-mat.str-el↗

arXiv1998

General Formulation of Quantum Analysis

A general formulation of noncommutative or quantum derivatives for operators in a Banach space is given on the basis of the Leibniz rule, irrespective of their explicit representations such as the Gâteaux derivative or commutators. This yields a unified formulation of quantum analysis, namely the invariance of quantum derivatives, which are expressed by multiple integrals of ordinary higher derivatives with hyperoperator variables. Multivariate quantum analysis is also formulated in the present unified scheme by introducing a partial inner derivation and a rearrangement formula. Operator Taylor expansion formulas are also given by introducing the two hyperoperators $ δ_{A \to B} \equiv -δ_A^{-1} δ_B$ and $d_{A \to B} \equiv δ_{(-δ_A^{-1}B) ; A}$ with the inner derivation $δ_A : Q \mapsto [A,Q] \equiv AQ-QA$. Physically the present noncommutative derivatives express quantum fluctuations and responses.

math-ph↗

arXiv1998

Does the Hubbard Model Show $d_{x^2-y^2}$ Superconductivity?

It is rigorously shown that the two-dimensional Hubbard model with narrow bands (including next nearest-neighbor hopping, etc.) does not exhibit $d_{x^2 -y^2}$-wave pairing long-range order at any nonzero temperature. This kind of pairing long-range order will also be excluded at zero temperature if an excited energy gap opens in the charge excitation spectrum of the system. These results hold true for both repulsive and attractive Coulomb interactions and for any electron fillings, and are consistent with quantum Monto Carlo calculations.

cond-mat.str-el↗

arXiv1995

Effect of the hole doping into the Haldane-gap state on the one-dimensional $S=1$ $t$-$J$ model

The ground state and excitation spectra of the $S=1$ Heisenberg spin chain with hole hopping are investigated by means of the numerical-diagonalization method and by the help of the Zhang-Arovas picture. As for the charge sector, two phases are found. It is shown that in the weak-hopping region, a phase separation occurs, while in the strong-hopping region, the system is in the Tomonaga-Luttinger liquid phase. Irrespective of the presence of the spin gap, the present phase diagram is similar to that reported for the $S=1/2$ $t$-$J$ chain with gapless spin excitation rather than to that for the magnetically-frustrated $t$-$J$ chain with spin gap. For the spin sector, the string correlation is found to develop withstanding the hole doping except in a region, whose region is characterized by a generalized string correlation. This remains an open question to be studied in future.

cond-mat↗

arXiv1995

Hidden Orders and RVB Formation of the Four-Leg Heisenberg Ladder Model

The ground state of the four-chain Heisenberg ladder model is numerically investigated. Hidden-order correlations suitable for the system are introduced and calculated with an emphasis on the spatially isotropic point, where a corresponding material exists. The existence of a long-range hidden correlation indicates formation of a short-range RVB state in the case of the antiferromagnetic inter-chain coupling. A transition between the phase of the ferromagnetic inter-chain coupling and that of the antiferromagnetic one is discussed.

cond-mat↗