Interplay between antiferromagnetic order and spin polarization in ferromagnetic metal/electron-doped cuprate superconductor junctions

Pok-Man Chiu; C. S. Liu; W. C. Wu

doi:10.1103/PhysRevB.79.064509

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Interplay between antiferromagnetic order and spin polarization in ferromagnetic metal/electron-doped cuprate superconductor junctions

Pok-Man Chiu, C. S. Liu, W. C. Wu

DOI 10.1103/PhysRevB.79.064509 · Physical Review B

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Abstract

Recently we proposed a theory of point-contact spectroscopy and argued that the splitting of zero-bias conductance peak in electron-doped cuprate superconductor point-contact spectroscopy is due to the coexistence of antiferromagnetic (AF) and d-wave superconducting orders [Phys. Rev. B 76, 220504(R) (2007)]. Here we extend the theory to study the tunneling in the ferromagnetic metal/electron-doped cuprate superconductor (FM/EDSC) junctions. In addition to the AF order, the effects of spin polarization, Fermi-wave vector mismatch between the FM and EDSC regions, and effective barrier are investigated. It is shown that there exists midgap surface-state contribution to the conductance to which Andreev reflections are largely modified due to the interplay between the exchange field of ferromagnetic metal and the AF order in EDSC. Low-energy anomalous conductance enhancement can occur which could further test the existence of AF order in EDSC. Finally, we propose a more accurate formula in determining the spin-polarization value in combination with the point-contact conductance data.