Angle-resolved resistivity method for precise measurements of electronic nematicity

Abstract

Electronic nematicity is an intriguing phenomenon found in unconventional superconductors and its mechanism invokes intense studies. The precise measurement of the director and amplitude of electronic nematicity by electric transport demands a full mapping of the longitudinal and transverse resistivity, $\ensuremath{\rho}$ and ${\ensuremath{\rho}}_{T}$, along different directions. Fabricating Hall bars along every possible in-plane direction would be so labor intensive and vulnerable to sample to sample variations that it becomes impractical. Instead, here we make the local current density $\mathbit{J}$ continuously rotate in plane by independently controlling its in-plane components along two orthogonal axes and measure $\ensuremath{\rho}$ and ${\ensuremath{\rho}}_{T}$ as a function of the azimuth angle $\ensuremath{\phi}$ between $\mathbit{J}$ and the crystallographic $[100]$ direction. Clear substantial angular oscillations in $\ensuremath{\rho}(\ensuremath{\phi})$ and ${\ensuremath{\rho}}_{T}(\ensuremath{\phi})$ were observed from the optimally doped ${\mathrm{La}}_{1.84}{\mathrm{Sr}}_{0.16}\mathrm{Cu}{\mathrm{O}}_{4}$ film, in stark contrast to those of the control gold film. This angle-resolved resistivity method demonstrates unprecedented precision in determining the director and amplitude of electronic nematicity and is applicable to anisotropic transport due to mechanisms other than electronic nematicity as well. This method paves the way for the studies of the nematic domains and fluctuations of the nematic order in films and bulk crystals.