Fulde-Ferrel-Larkin-Ovchinnikov Inhomogeneous Superconducting State and Phase Transitions Induced by Spin Accumulation in a ferromagnet-dx2-y2-wave superconductor-ferromagnet tunnel junction

Biao Jin, Gang Su,* and Qing-Rong Zheng

College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049, China

Received 11 July 2005; revised manuscript received 19 December 2005; published 24 February 2006

ABSTRACT

    Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting (SC) state, first- and second-order phase transitions, and quantum criticality induced by spin accumulation in a ferromagnet-dx2y2-wave superconductor-ferromagnet tunnel junction are theoretically predicted. A complex phase diagram in the temperature-bias voltage plane is determined. It is found that the phase transitions from the homogeneous BCS state to the inhomogeneous FFLO state, and from the FFLO state with the momentum q’s azimuthal angle θq=0 to that with θq=π/4, are of the first order, whereas the transitions from all SC states to the normal state at critical voltages are of the second order. A Lifshitz point, a bicritical point, and a quantum critical point are identified.

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