The superconductivity of Sr2RuO4 under c-axis uniaxial stress
Fabian Jerzembeck, Henrik S. Røising, Alexander Steppke, H. Rösner, D. A. Sokolov, Naoki Kikugawa, Thomas Scaffidi, Steven H. Simon, A. P. Mackenzie, Clifford W. Hicks
Abstract
Abstract Applying in-plane uniaxial pressure to strongly correlated low-dimensional systems has been shown to tune the electronic structure dramatically. For example, the unconventional superconductor Sr 2 RuO 4 can be tuned through a single Van Hove point, resulting in strong enhancement of both T c and H c2 . Out-of-plane ( c axis) uniaxial pressure is expected to tune the quasi-two-dimensional structure even more strongly, by pushing it towards two Van Hove points simultaneously. Here, we achieve a record uniaxial stress of 3.2 GPa along the c axis of Sr 2 RuO 4 . H c2 increases, as expected for increasing density of states, but unexpectedly T c falls. As a first attempt to explain this result, we present three-dimensional calculations in the weak interaction limit. We find that within the weak-coupling framework there is no single order parameter that can account for the contrasting effects of in-plane versus c -axis uniaxial stress, which makes this new result a strong constraint on theories of the superconductivity of Sr 2 RuO 4 .