Charge stripes, nematicity and disorder in a cuprate superconductor

Charge stripe order is recognized as an important ingredient of the physics of cuprates, yet the thermodynamics of its formation and the influence of disorder are unclear. We present a study of the development of charge stripes in the cuprate La$_{1.8−x}$Eu$_{0.2}$Sr$_x$CuO$_4$, using three complementary experimental techniques: nuclear quadrupole resonance, nonlinear conductivity and specific heat\footnote{D. Pelc et al., \textit{Nature Comm.} \textbf{7}, 12775 (2016)}. We find an intermediate phase between (pseudogapped) metal and charge stripes, existing in a dome-shaped region of the phase diagram and appearing through a sharp phase transition. A novel technique\footnote{M. Do\v{s}li\'{c}, D. Pelc, M. Po\'{z}ek, \textit{Rev. Sci. Instr.} \textbf{85}, 073905 (2014)} is used for measurements of nonlinear response, which show that the new phase is consistent with a charge nematic. This is in agreement with recent predictions of charge stripe formation with quenched disorder\footnote{L. Nie, G. Tarjus, S. Kivelson, \textit{Proc. Nat. Acad. Sci. USA} \textbf{111}, 7980 (2014)}. Our experiments thus resolve the intricate process of charge stripe formation and provide a link to other materials with electronic nematic order.