Studies of anomalous superconducting properties near a quantum critical point by precision specific heat measurements

2014 Fiscal Year Final Research Report

• Project/Area Number: 25610096
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: The University of Tokyo
• Principal Investigator: SHIBAUCHI Takasada 東京大学, 新領域創成科学研究科, 教授 (00251356)
• Project Period (FY): 2013-04-01 – 2015-03-31
• Keywords: 量子臨界現象 / 超伝導特性 / 準粒子励起 / 臨界磁場 / 反強磁性 / 渦糸物理 / 有効質量 / 磁場侵入長

Outline of Final Research Achievements

In the vicinity of a quantum critical point, which marks a phase transition at zero temperature, physical properties exhibit deviations from the standard Fermi-liquid theory of metals, and sometimes unconventional superconductivity emerges. An important issue is to clarify the relationship between this superconductivity and the quantum critical fluctuations. In this project, we studied quasiparticle excitations in the superconducting state near a quantum critical point in iron-based superconducting materials. We found that the effective electron mass estimated from the jump in the specific heat at the superconducting transition gives a quantitative agreement with the zero-temperature penetration depth results, showing a divergent increase towards the quantum critical point. Moreover, the vortex core energy also shows an anomalous increase. These results evidence that the quantum criticality affects strongly the electronic state deep inside the superconducting phase.

Free Research Field

固体電子物性