Pseudogaps in underdoped cuprates

摘要: Abstract It has become clear in the past several years that cuprates show many unusual properties, both normal and superconducting (SC) states, especially underdoped region. In particular, gap-like behavior is observed magnetic c -axis conductivity photoemission, whereas in-plane transport properties are only slightly affected by pseudogap. I shall argue these experimental evidences must be viewed context of physics a doped Mott insulator they support notion spin charge separation. review recent theoretical developments, concentrating on studies based t – J model. describe model quasiparticle (qp) excitations, which predicts doping dependence T anomalous energy-gap-to- ratios. Finally, outline how may derived from microscopic formulation After brief U(1) formulation, explain some difficulties encountered there, new SU(2) can resolve difficulties.