A prominent manifestation of the competition between repulsive and attractive interactions acting on different length scales is the self-organized ordering of electrons in a stripelike fashion in material systems such as high-$T_c$ superconductors. Such stripe phases are also believed to occur in two-dimensional electron systems exposed to a perpendicular magnetic field, where they cause a strong anisotropy in transport. The addition of an in-plane field even enables us to expel fractional quantum Hall states, to the benefit of such anisotropic phases. An important example represents the disappearance of the $5/2$ fractional state. Here, we report the use of nuclear magnetic resonance spectroscopy to probe the electron density distribution of this emergent anisotropic phase. A surprisingly strong spatial density modulation was found. The observed behavior suggests a stripe pattern with a period of $2.6\pm 0.6$ magnetic lengths and an amplitude as large as 20% relative to the total density.

• Received 27 March 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.076803