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Unconventional superconductivity in CeCoIn5 with magnetic texture and orbital quantization

H. A. Radovan·N. A. Fortune·T. P. Murphy·S. T. Hannahs·E. C. Palm·S. W. Tozer·D. Hall
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Abstract

A sufficiently high magnetic field applied to a superconductor will act on both the charge and the spin of the individual electrons breaking up the Cooper pairs. If the spin effect dominates, the superconducting state can develop a texture before eventually entering the normal state with increasing magnetic field. This spatially varying superconducting state is a periodic array of magnetic walls separated by superconducting regions. Known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, it was predicted in 1964. We report heat capacity measurements on the heavy fermion superconductor, CeCoIn5, which reveal a second phase transition within the superconducting state, clear evidence of the FFLO phase. We also report magnetization measurements that display a cascade of first order phase transitions within the FFLO region. Each transition indicates an increase in orbital momentum of the superconducting order parameter and corresponds to a specific Landau level vortex state comprised of multiquanta vortices. The experimental realization of the FFLO state provides a new opportunity to study the symbiosis of magnetism and superconductivity, two states of matter once thought to be mutually exclusive.

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H. A. Radovan, N. A. Fortune, T. P. Murphy, S. T. Hannahs, E. C. Palm, S. W. Tozer, D. Hall. 2003-04-23. Unconventional superconductivity in CeCoIn5 with magnetic texture and orbital quantization. https://arxiv.org/abs/cond-mat/0304526

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