Spin-Triplet Superconductivity with Line Nodes in Sr_<b>2</b>RuO_<b>4</b>

Abstract

Several possible odd-parity states are listed up group-theoretically and\nexamined in light of recent experiments on Sr$_2$RuO$_4$. Those include some of\nthe $f$-wave pairing states, ${\\mib d}({\\mib k})\\propto{\\hat{\\mib z}}\nk_xk_y(k_x + {\\rm i}k_y)$ and ${\\hat{\\mib z}} (k_x^2-k_y^2)(k_x + {\\rm i}k_y)$\nand other ${\\hat{\\mib z}} (k_x + {\\rm i}k_y)\\cos ck_z$ ($c$ is the $c$-axis\nlattice constant) as most plausible candidates. These are time-reversal\nsymmetry broken states and have line nodes running either vertically (the\nformer two) or horizontally (the latter), consistent with experiments.\nCharacterizations of these states and other possibilities are given.\n