Evidence for charged critical fluctuations in underdoped Y-123
  We report and analyze in-plane penetration depth measurements in YBa2Cu3O7-x taken close to the critical temperature Tc. In underdoped YBa2Cu3O6:59 we find consistent evidence for charged critical behavior. Noting that the effective dimensionless charge scales as 1/sqrt(Tc), this new critical behavior should be generically observable in suitably underdoped cuprates. 
T. Schneider, R. Khasanov, K. Conder, E. Pomjakushina, R. Bruetsch and   H. Keller