講演題目：　Physics of high Tc superconductivity:　
　　　　　　　the role of spin and charge excitations (spinons and holons)

講　師　：　Sung-Ho Salk　
　　　　　　　　（韓国ポハン大学・教授）
　　　　　　　　 
日　時　：　平成14年8月8日（木）　14:00-
場　所　：　北海道大学大学院理学研究科物理学専攻　大学院講義室
　　　　　　　理学部　2号館（2−11号室）

要　旨　：
　 　High Tc superconductivity is one of the most challenging subjects incondensed matter physics for both fundamentals and　applications.In　the area of its basics one of the most　searched subjects is the mechanism of superconductivity for doped cuprates, which still remains to be resolved. First, multifaceted aspects of experimental observations will be briefly reviewed. They are the ARPES, STM, muSR, NMR, NQR, INS, optical concuctivity measurements and specific heat measurements. Based on these observations we then make a judicious review of various proposed theories by paying attention to the charge and spin degrees of freedom. These theories include the original RVB theory, slave-boson theories of U(1) and SU(2), SO(5), DDW, CDW and numerical simulations. We then introduce our theory of slave-boson theory which differs from the earlier ones developed by other researchers especially in　the treatment of Heisenbeg term. By paying a rigorous　 attention to the spin and charge degrees of freedom we explain the physics of why this new theory predicts well in agreement with numerous observations, including the muSR measurements of superfluid weight vs. Tc and specific heat measurements. Time permitting we will also discuss the vortex binding-unbinding transition at low temperatures in the underdoped region.

世話人　小田　研　（北海道大学大学院理学研究科）
　　　　　　　　　 (011-706-3575、moda@sci.hokudai.ac.jp)