Superconductivity and quantum transport phenomena in Jahn-Teller crystals

2014 Fiscal Year Final Research Report

• Project/Area Number: 24540379
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: HOTTA Takashi 首都大学東京, 理工学研究科, 教授 (00262163)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: ヤーンテラーフォノン / 近藤効果 / ラットリング / バイブロニック状態 / 磁性 / 軌道自由度 / 超伝導 / フェルミ面

Outline of Final Research Achievements

We have analyzed the superconducting transition temperature Tc in the two-dimensional orbital-degenerate electron systems coupled with Jahn-Teller oscillations. We have found that Tc is increased for the case of disconnected Fermi-surface structure, since Cooper-pair hopping between different Fermi surfaces is enhanced by the Jahn-Teller oscillation.
We have analyzed the Anderson model coupled with anharmonic Jahn-Teller oscillations by using a numerical renormalization group technique. We have found that the Kondo phenomenon occurs due to the screening of rotational phonon mode with clockwise and anti-clockwise directions by orbital momenta of conduction electrons.
We have discovered chaos in the energy spectrum of anharmonic Jahn-Teller oscillation. We have pointed out that chaos appears as an anomalous peak in the temperature dependence of specific heat. We have proposed that such a peak can be detected in the experiments on cage-structure materials.

Free Research Field

物性理論