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[ISSP Colloquiums]
Contrasting criticalities in the cuprates and pnictides
Title : Contrasting criticalities in the cuprates and pnictides
Date :
Time :
4:00 PM - 5:00 PM 
Place : Lecture Room (A632), 6th Floor, ISSP   
Lecturer : Prof. Nigel Hussey
Affiliation : High Field Magnet Laboratory (HFML)
Summary : The physics of quantum critical phase transitions connects to some of the most difficult problems in condensed matter physics, including metal-insulator transitions, frustrated magnetism and high temperature superconductivity. Near a quantum critical point (QCP) a new kind of metal emerges, whose thermodynamic and transport properties do not fit into the unified phenomenology of Landau Fermi liquid theory - characterized by a specific heat that is linear in temperature and an electrical resistivity that varies as the square of the absolute temperature. Studying the evolution of the temperature dependence of these observables as a function of a control parameter leads to the identification both of the presence and the nature of the quantum phase transition in candidate systems.
In this talk, I will review my group's work following the evolution of the in-plane transport properties of copper- and iron-based superconductors at temperatures below the superconducting transition temperature Tc by suppressing superconductivity with high magnetic fields (both static and pulsed). One of the striking observations from this study is the distinct behaviour found in the pnictide superconductors when compared with their cuprate counterparts. This dichotomy reveals a deep fundamental difference between the two families of high temperature superconductors, and while the transport behaviour of the iron pnictides might be associated with conventional quantum critical scenarios in which a magnetic ordering transition falls to 0 K with doping, for the cuprates, an entirely different and novel theoretical framework may be required. This difference is also closely tied to the mystery and the origin of the normal state pseudogap found in cuprates with low carrier concentrations.
Contact : Hiroshi NOGUCHI(ext.63265),Minoru YAMASHITA(ext.63350)