Revival of superconductivity in high magnetic fields and a possible p-wave pairing in (TMTSF)2PF6

From the BCS theory, we derive an equation which accounts for quantum effects of an electron motion along open Fermi surfaces and determines the upper critical field H-c2(perpendicular to)(T) perpendicular to the chains of a quasi-one-dimensional conductor. This equation demonstrates two unusual phenomena: (1) restoration of superconductivity at H>H-c2(perpendicular to)(0) in p-wave superconductors, where H-c2(perpendicular to)(0) is the quasiclassical upper critical field; (2) surviving of superconductivity at H-c2(perpendicular to)(0), H-p<H<H-p(LOFF) in s-wave superconductors, where H-p is the Clogston-Chandrasekhar paramagnetic limiting field; the critical held H-p(LOFF) is introduced in the paper. An analysis of recent experimental data by I. J. Lee, M. J. Naughton, G. M. Danner, and P. M; Chaikin [Phys. Rev. Lett. 78, 3555 (1997)] shows that superconductivity significantly exceeds H-p(LOFF) for b direction of a magnetic field in (TMTSF)(2)PF6. This demonstrates a strong suppression of the Pauli pair breaking effects and may reflect ap-wave pairing of electrons. [S0163-1829(99)50302-0].