Enhancement of the London Penetration Depth in Pnictides at the Onset of Spin-Density-Wave Order under Superconducting Dome

A. Levchenko, M. G. Vavilov, M. Khodas, A. V. Chubukov
2013 Physical Review Letters  
Recent measurements of the doping dependence of the London penetration depth \lambda(x) at low temperatures in clean samples of isovalent BaFe_2[As_(1-x)P_x]_2 at T<<Tc [Hashimoto et al., Science 336, 1554 (2012)] revealed a peak in \lambda(x) near optimal doping x=0.3. The observation of the peak at T<<Tc, points to the existence of the quantum critical point (QCP) beneath the superconducting dome. We associate such a QCP with the onset of a spin- density-wave order and show that the
more » ... that the renormalization of \lambda(x) by critical magnetic fluctuations, gives rise to the observed feature. We argue that the case of pnictides is conceptually different from a one-component Galilean invariant Fermi liquid, for which correlation effects do not cause the renormalization of the London penetration depth at T=0.
doi:10.1103/physrevlett.110.177003 pmid:23679761 fatcat:u44jtevturaznkncyfhzyt6bre