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Takashi Yamamoto

Publications and source records attributed to Takashi Yamamoto.

101 records · Page 6Linked to original sources
arXiv1999

Exact Dynamics of the SU(K) Haldane-Shastry Model

The dynamical structure factor $S(q,ω)$ of the SU(K) (K=2,3,4) Haldane-Shastry model is derived exactly at zero temperature for arbitrary size of the system. The result is interpreted in terms of free quasi-particles which are generalization of spinons in the SU(2) case; the excited states relevant to $S(q,ω)$ consist of K quasi-particles each of which is characterized by a set of K-1 quantum numbers. Near the boundaries of the region where $S(q,ω)$ is nonzero, $S(q,ω)$ shows the power-law singularity. It is found that the divergent singularity occurs only in the lowest edges starting from $(q,ω) = (0,0)$ toward positive and negative q. The analytic result is checked numerically for finite systems via exact diagonalization and recursion methods.

cond-mat.str-el↗
arXiv1999

Exact dynamical structure factor of the degenerate Haldane-Shastry model

The dynamical structure factor $S(q,ω)$ of the K-component (K = 2,3,4) spin chain with the 1/r^2 exchange is derived exactly at zero temperature for arbitrary size of the system. The result is interpreted in terms of a free quasi-particle picture which is generalization of the spinon picture in the SU(2) case; the excited states consist of K quasi-particles each of which is characterized by a set of K-1 quantum numbers. Divergent singularities of $S(q,ω)$ at the spectral edges are derived analytically. The analytic result is checked numerically for finite systems.

cond-mat.str-el↗
arXiv1999

Dynamical correlation functions of the spin Calogero-Sutherland model

The thermodynamic limit of the dynamical density and spin-density two-point correlation functions for the spin Calogero-Sutherland model are derived from Uglov's finite-size results. The resultant formula for the density two-point correlation function is consistent with the previous conjecture on the basis of the minimal number of elementary excitations.

cond-mat.str-el↗
arXiv1999

Exact Charge Dynamics in the Supersymmetric t-J Model with Inverse-Square Interaction

Dynamical charge structure factor $N(Q,ω)$ with $Q$ smaller than the Fermi wave number is derived analytically for the one-dimensional supersymmetric t-J model with $1/r^2$ interaction. Strong spin-charge separation in dynamics is found. $N(Q,ω)$ with given electron density does not depend on the spin polarization for arbitrary size of the system. In the thermodynamic limit, only two holons and one antiholon contribute to $N(Q,ω)$. These results together with generalized ones for the SU($K$,1) supersymmetric t-J model are derived via solution of the Sutherland model in the strong coupling limit.

cond-mat.str-el↗
arXiv1997

Boundary bound states for the open Hubbard chain with boundary fields

The boundary effects in the open Hubbard chain with boundary fields are studied. The boundary string solutions of the Bethe ansatz equations that give rise to a wave functions localized at the boundary and exponentially decreasing away from the boundary are provided. In particular, it is shown that the correct ground state of the model at half-filling contains the boundary strings.

cond-mat.str-el↗
arXiv1997

Elementary Excitations and Dynamical Correlation Functions of the Calogero-Sutherland Model with Internal Symmetry

We consider the physical properties of elementary excitations of the Calogero-Sutherland (CS) model with SU(K) internal symmetry. From the results on the thermodynamics of this model, we obtain the charge, spin, and statistics of elementary excitations. Combining this knowledge and the known results on the dynamics in the spinless CS model, we propose the expression for the dynamical correlation functions of the SU(K) CS model. In the asymptotic region, we confirm the consistency of our results with predictions from conformal field theory.

cond-mat.str-el↗
arXiv1996

Integrable $1/r^2$ Spin Chain with Reflecting End

A new integrable spin chain of the Haldane-Shastry type is introduced. It is interpreted as the inverse-square interacting spin chain with a {\it reflecting end}. The lattice points of this model consist of the square roots of the zeros of the Laguerre polynomial. Using the ``exchange operator formalism'', the integrals of motion for the model are explicitly constructed.

cond-mat↗
arXiv1995

Multicomponent Calogero Model of $B_N$-Type Confined in Harmonic Potential

A new one-dimensional model, the multicomponent Calogero model of $B_N$-type confined in the harmonic potential, is introduced. The Lax pair of this model is determined, and then a set of functionally independent conserved operators are constructed. Moreover, the energy spectrums of the above model are obtained by three different methods.

cond-mat↗
arXiv1995

Critical Properties of the Calogero-Sutherland Model with Boundaries

Critical properties of the Calogero-Sutherland model of $BC_N$-type ($BC_N$-CS model) are studied. Using the asymptotic Bethe-ansatz spectrum of the $BC_N$-CS model, we calculate finite-size corrections in the energy spectrum. Since the $BC_N$-CS model does not possess translational invariance, the finite-size spectrum acquires the contributions coming from ``boundaries''. We show that the low-energy critical behavior of the model is described by $c=1$ boundary conformal field theory. Thus the universality class of the model is identified as a chiral Tomonaga-Luttinger liquid.

cond-mat↗