Study on quantum degenerated phases in electron and hole system in semiconductors

2014 Fiscal Year Final Research Report

• Project/Area Number: 22244036
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Condensed matter physics I
• Research Institution: The University of Tokyo
• Principal Investigator: SHIMANO Ryo 東京大学, 低温センター, 教授 (40262042)
• Project Period (FY): 2010-04-01 – 2015-03-31
• Keywords: 電子正孔系 / 励起子モット転移 / 電子正孔BCS / 励起子ボースアインシュタイン凝縮 / テラヘルツ / 半導体 / 超高速現象 / ヒッグスモード

Outline of Final Research Achievements

We investigated the possibility of quantum degenerate phases, namely the exciton Bose-Einstein condensation and electron-hole (e-h) BCS sate, in photoexcited semiconductors. We intensively studied the behavior of exciton Mott crossover in terms of the crossover problem between these quantum degenerate phases by using the terahertz time-domain spectroscopy. We succeeded in the determination of exciton ionization ratio as a function of temperature and density, from which we determined the phase diagram of e-h system in the Mott crossover density regime. We revealed the signature of unscreened e-h correlation in the metallic e-h gas system which may be related to the precursor of e-h BCS paring. We also investigated the nonequilibrium dynamics of a superconductor. We discovered that after the nonadiabatic excitation with a monocycle terahertz pulse, an oscillation of the amplitude of the order parameter, namely the Higgs amplitude mode appears.

Free Research Field

光物性物理学