「Pair-pair interactions in high-Tc superconductivity : evidence from tunneling experiments」
William Sacks 氏
Oct 25, 2016
日本物理学会北海道支部講演会
講演題目： Pair-pair interactions in high-Tc superconductivity : evidence from tunneling experiments
講 師 ： William Sacks 博士
Sorbonne Universities, Paris, France
日 時 ： 平成28年10月25日 (火) 16:30-18:00
場 所 ： 北海道大学理学部5号館5－206室
要 旨 ：
The conventional BCS theory fails to account for the physical properties of a large variety of high-Tc superconductors, the cuprate family and the recently discovered iron-based superconductors. In particular, these materials reveal a `peak-dip-hump' structure in the quasiparticle DOS at low temperature and often a pseudogap at the critical temperature. In my talk, the origin of these features are explained in the framework of a new pair-pair interaction model [1] : - The non-superconducting state consists of incoherent pairs, a `Cooper-pair glass' which, due to the pair-pair interaction, condense below Tc to the coherent superconducting state. - The peak-dip-hump structure is then due to the strong coupling between quasiparticles and excited pairs, which we call `super-quasiparticles'. The talk will focus on a wide variety of tunneling experiments, with varied temperature, magnetic field and doping, to test the validity of the model. [1] W. Sacks, A. Mauger, Y. Noat, Superconduct. Sci. Technol. 28 105014, (2015)
世話人 小田研
（moda@sci.hokudai.ac.jp）
北海道大学理学部物理学科 (電話011-706-3484)
「Electronic phase transitions through time - on a femtosecond timescale」
Prof. Dragan Mihailovic
Oct 25, 2016
日本物理学会北海道支部講演会
講演題目： Electronic phase transitions through time - on a femtosecond timescale
講 師 ： Prof. Dragan Mihailovic
Jozef Stefan institute, Ljubljana, Slovenia
日 時 ： 平成28年10月25日 (火) 16:30-18:00
場 所 ： 北海道大学 工学部 アカデミックラウンジ3
要 旨 ：
The study of phase transitions in real time under nonequilibrium conditions is of fundamental interest in many areas of physics. A special category of recent fundamental and practical interest are transitions to metastable hidden states which occur under conditions of particle-hole asymmetry. While such behavior has been invoked in cosmology to explain Baryogenesis, it is not commonly observed elsewhere. In the quasi-two-dimensional dichalcogenide, 1T-TaS2, conditions for the formation of an electronically textured hidden “false vacuum” state are created by femtosecond laser photoexcitation. Femtosecond photoexcited low temperature scanning tunneling microscopy reveals a remarkable quantum duality of polaron behavior with a vivid real-space illustration of Mott physics. The current system is of practical interest for ultrafast low-energy low-temperature non-volatile memory devices with applications in cryogenic computing.
世話人 戸田 泰則
北海道大学工学部応用理工系学科 (電話011-706-6115)
