Zeeman and orbital limiting magnetic fields in cuprates: The pseudogap connection

Abstract

In cuprates, in a view where pairing correlations set in at the pseudogap energy scale T* and acquire global coherence at a lower temperature T c, the region Tc ≤ T ≤ T* is a vast fluctuation regime. Tc and T* vary differently with doping and the question remains about the doping trends of the relevant magnetic field scales: the field Hc2 bounding the superconducting response and the pseudogap closing field Hpg. In-plane thermal (Nernst) and our interlayer (tunneling) transport experiments in Bi2Sr 2CaCu2O8+y report hugely different limiting magnetic fields. Here, based on pairing (and the uncertainty principle) combined with the definitions of the Zeeman energy and the magnetic length, we show that both fields convert to the same pseudogap scale T* upon transformation as orbital and Zeeman critical fields, respectively. The region of superconducting coherence is confined to the 'dome' that coincides with the usual unique upper critical field Hc2 on the strongly overdoped side. We argue that the distinctly different orbital and the Zeeman limiting fields can co-exist owing to charge and spin degrees of freedom separated to different parts of the strongly anisotropic Fermi surface. © Indian Academy of Sciences.