Grant-in-Aid for Scientific Research on Priority Areas
|Allocation Type||Single-year Grants |
|Research Institution||Tokyo Institute of Technology |
SHIBA Hiroyuki Tokyo Inst. Tech., Physics Dept., Prof., 理学部, 教授 (30028196)
SAKAI Osamu Tohoku Univ., Physics Dept., Assoc.Prof., 理学研究科, 助教授 (60005957)
MIYAKE Kazumasa Osaka Univ., Dept. of Cont. Mat., Prof., 基礎工学部, 教授 (90109265)
MACHIDA Kazushige Okayama Univ., Phys. Dept., Prof., 理学部, 教授 (50025491)
KURAMOTO Yoshio Tohoku Univ., Physics Dept., Prof., 理学研究科, 教授 (70111250)
HASERGAWA Akira Niigata Univ., Physics Dept., Prof., 理学部, 教授 (40004329)
山田 耕作 京都大学, 理学部, 助教授 (90013515)
|Project Period (FY)
1994 – 1997
Completed (Fiscal Year 1997)
|Budget Amount *help
¥44,800,000 (Direct Cost: ¥44,800,000)
Fiscal Year 1997: ¥10,800,000 (Direct Cost: ¥10,800,000)
Fiscal Year 1996: ¥11,000,000 (Direct Cost: ¥11,000,000)
Fiscal Year 1995: ¥11,000,000 (Direct Cost: ¥11,000,000)
Fiscal Year 1994: ¥12,000,000 (Direct Cost: ¥12,000,000)
|Keywords||superconductivity / heavy fermious / non-fermi liquid / quadrunpole ordering / Kondo effect / Kondo semiconductor / band structure calculation / uranium compound / 四重極子秩序 / 近藤絶縁体 / 四重極近藤効果 / バンド理論 / 異常ホール効果|
The Theory Group of Research Project "Physics of Strongly Correlated Conducting Electrons" has carried out research in close collaboration with the Experiment Group. The main results during the 4 years are as follows.
(1) Among many f-electron superconductors UPt3 having plural superconducting phases is clearly unconventional in the nature of superconductivity. On this material Kitaoka et. al. (Osaka Univ.) and Sakakibara (Hokkaido Univ.) have carried out detailed NMR and magnetic measurements. Machida (Okayama Univ.) has proposed a scenario of triplet superconductivity to explain those experiments based on a phenomenological theory. It is the next important problem to give a microscopic origin of the superconductivity.
(2) It is a common wisdom that magnetic impurities in metals usually turn to Fermi liquid at low temperatures. However, Sakakibara et. al. found that ThRuィイD22ィエD2SiィイD22ィエD2 containing dilute U shows non-Fermi liquid behavior. This problem was theoretically studied by 3
groups, Shiba (Tokyo Inst. Tech.), Sakai (Tohoku Univ.) and Miyake (Osaka Univ.). The results show that when the crystal field ground state is non-Kramers doublet and well separated from excited states, two-channel-Kondo non-Fermi liquid is possible, while it is taken over by Fermi liquid when the excited states become low. Sakai and his coworkers determined the temperature dependence of various physical quantities by using numerical renormalization group method.
(3) Because of orbital degrees of freedom the ordered phase of some f-electron systems are complicated. In addition to ordinary magnetic orderings one can have an ordered phase related to quadrupole moments. CeBィイD26ィエD2 a typical example of this sort. The nature of the ordered phase in magnetic fields in particular had been a matter of controversy. Shiba and Sakai studied this problem and showed that in CeBィイD26ィエD2 the field-induced octupoles are sizable and important to explain the NMR shifts, which had been a mystery for a long period. In this connection Kuramoto (Tohoku Univ.) presented a theory of fluctuating quadrupoles.
(4) Miyake presented a theory of Kondo semiconductors, taking into account the k-dependence of mixing matrix elements. It explains well experimental results of CeNiSn, which Takabatake (Hiroshima Univ.) studied experimentally.
(5) Band structure calculations have been carried out on many rare-earth compounds by Hasegawa (Niigata Univ.) and Harima (Osaka Univ.). They have brought important information on electronic structure through a comparison with de Hans- van Alphen experiments by Onuki (Osaka Univ.). Hasegawa et. al. have develped a theory of relativistic current and spin density functional. It is hoped that it is successfully applied to actinide compounds. Less