arXiv subjects

Kazumasa Hattori

Publications and source records attributed to Kazumasa Hattori.

41 records · Page 3Linked to original sources

arXiv2006

Realization of Strong Coupling Fixed Point in Multilevel Kondo Models

Impurity four- and six-level Kondo model, in which an ion is tunneling among four- and six-stable points and interacting with surrounding conduction electrons, are investigated by using the perturbative and numerical renormalization group methods. It is shown that purely orbital Kondo effects occur at low temperatures in these systems which are direct generalizations of the Kondo effect in the so-called two-level system. This result offers a good explanation for the enhanced and magnetically robust Sommerfeld coefficient observed in SmOs_4Sb_12 and some other filled-skutterudites.

cond-mat.str-el↗

arXiv2005

Critical Nature of Non-Fermi Liquid in Spin 3/2 Multipolar Kondo Model

A multipolar Kondo model of an impurity spin S_I=3/2 interacting with conduction electrons with spin s_c=3/2 is investigated using boundary conformal field theory. A two-channel Kondo (2CK) -like non-Fermi liquid (NFL) under the particle-hole symmetry is derived explicitly using a ``superspin absorption'' in the sector of a hidden symmetry, SO(5). We discuss the difference between the usual spin-1/2 2CK NFL fixed point and the present one. In particular, we find that, unlike the usual 2CK model, the low temperature impurity specific heat is proportional to temperature.

cond-mat.str-el↗

arXiv2005

Local Heavy Quasiparticle in Four-Level Kondo Model

An impurity four-level Kondo model, in which an ion is tunneling among 4-stable points and interacting with surrounding conduction electrons, is investigated using both perturbative and numerical renormalization group methods. The results of numerical renormalization group studies show that it is possible to construct the ground state wavefunction including the excited ion states if we take into account the interaction between the conduction electrons and the ion. The resultant effective mass of quasiparticles is moderately enhanced. This result offers a good explanation for the enhanced and magnetically robust Sommerfeld coefficient observed in SmOs$_4$Sb$_{12}$, some other filled-skutterudites, and clathrate compounds.

cond-mat.str-el↗

arXiv2005

Realization of Heavy Local Fermi Liquid and Non-Fermi Liquid in f$^2$ Crystalline-Electric-Field Singlet-Triplet Configuration

Using the numerical renormalization group method, we investigate an extended Anderson model, in which correlated electrons with the $Γ_1$(singlet)-$\Gamma4$(triplet) f$^2$ crystalline-electric-field (CEF) configuration hybridize with conduction electrons of $Γ_7$(doublet) and $Γ_8$ (quartet) under cubic $O_h$ symmetry, from a strong spin-orbit interaction limit. For the case of the parameters relevant to PrFe4P12, the system is under competition between the CEF singlet fixed point and the multichannel Kondo non-Fermi liquid fixed point arising from the quadrupolar coupling between the impurity with pseudospin 1 and the conduction electron with pseudospin 3/2 . We consider that this result reveals the origin of the heaviness of the effective mass and non-Fermi liquid behavior of the Pr- based filled skutterudite compounds.

cond-mat.str-el↗

arXiv2005

Quasiparticle Interactions for f$^2$-Impurity Anderson Model with Crystalline-Electric-Field: Numerical Renormalization Group Study

The aspect of the quasiparticle interaction of a local Fermi liquid, the impurity version of f$^2$-based heavy fermions, is studied by the Wilson numerical renormalization group method. In particular, the case of the f$^2$-singlet crystalline-electric-field ground state is investigated assuming the case of UPt$_3$ with the hexagonal symmetry. It is found that the interorbital interaction becomes larger than the intraorbital one in contrast to the case of the bare Coulomb interaction for the parameters relevant to UPt$_3$. This result offers us a basis to construct a microscopic theory of the superconductivity of UPt$_3$ where the interorbital interactions are expected to play important roles.

cond-mat.str-el↗