Theory of photoinduced superconductivity and nonequilibrium phase transition in complex correlated quantum systems

2015 Fiscal Year Final Research Report

• Project/Area Number: 25800192
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Institute of Physical and Chemical Research (2015); The University of Tokyo (2013-2014)
• Principal Investigator: Tsuji Naoto 国立研究開発法人理化学研究所, 創発物性科学研究センター, 研究員 (90647752)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 超伝導 / 動的平均場理論 / 非平衡 / 光誘起超伝導

Outline of Final Research Achievements

We reveal that there exists a supersolid phase (coexistence of superconductivity and charge order) accompanied by a quantum critical point in strongly coupled electron-phonon systems. Using the nonequilibrium dynamical mean-field theory, we show that the superconducting phase has a new collective amplitude mode hybridizing with a phonon oscillation, in addition to the Higgs amplitude mode. We also show that when the superconducting phase is driven by an oscillating electric field, the superconducting order parameter is forced to oscillate with a doubled frequency. The forced oscillation can be resonantly enhanced when the doubled frequency coincides with the Higgs mode frequency. This phenomenon has been observed in a THz laser experiment.

Free Research Field

物性理論