Interlayer spin-singlet pairing induced by magnetic interactions in an antiferromagnetic su.pdfVIP

a r X i v : c o n d - m a t / 0 4 0 7 2 8 1 v 2 [ c o n d - m a t .s u p r - c o n ] 2 1 S e p 2 0 0 5 Interlayer spin-singlet pairing induced by magnetic interactions in an antiferromagnetic superconductor Hiroshi Shimahara Department of Quantum Matter Science, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan (Dated: Received 11 July 2004) It is shown that interlayer spin-singlet Cooper pairing is induced by magnetic interactions in a metallic antiferromagnet of stacked conductive layers in which each layer is ferromagnetically polar- ized and they order antiferromagnetically in stacking direction. As a result, the antiferromagnetic long-range order and superconductivity coexist at low temperatures. It is shown that TAF Tc except for in a very limited parameter region unless TAF = 0, where TAF and Tc denote the antifer- romagnetic and superconducting transition temperatures, respectively. It is found that the exchange field caused by the spontaneous staggered magnetization does not affect superconductivity at all, even if it is very large. The resultant superconducting order parameter has a horizontal line node, and is isotropic in spin space in spite of the anisotropy of the background magnetic order. We discuss the possible relevance of the present mechanism to the antiferromagnetic heavy fermion superconductors UPd2Al3 and CePt3Si. PACS numbers: 74.20.-z, 74.20.Mn, 74.20.Rp 74.25.Ha In this paper, we show that interlayer spin-singlet Cooper pairing is induced by magnetic interactions in a certain kind of metallic antiferromagnet. We consider a layered system of itinerant electrons in which each layer is ferromagnetically polarized but the majority-spin alter- nates in stacking direction. Therefore, the magetic order is characterized by the wave vectorQ = (0, 0, π/c), where we have assumed the a and b crystal axes to be parallel to the layers, and the c-axis in the stacking direction, and c denotes the c-axis lattice constant. It is also sho