Majorana zero modes in semiconductor nanowires in contact with higher-T_c superconductors

We analyze the prospects for stabilizing Majorana zero modes in semiconductor nanowires that are proximity coupled to higher-temperature superconductors. We begin with the case of iron pnictides which, though they are s-wave superconductors, are believed to have superconducting gaps that change sign. We then consider the case of cuprate superconductors. We show that a nanowire on a steplike surface, especially in an orthorhombic material such as YBCO, can support Majorana zero modes at an elevated temperature.