Upper critical field for underdoped high-T_c superconductors. Pseudogap and stripe--phase

摘要

We investigate the upper critical field in a stripe--phase and in thepresence of a phenomenological pseudogap. Our results indicate that theformation of stripes affects the Landau orbits and results in an enhancement of$H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to areduction of the upper critical field. This effect is of particular importancewhen the magnitude of the gap is of the order of the superconducting transitiontemperature. We have found that a suppression of the upper critical field takesplace also for the gap that originates from the charge--density waves.