Competing charge density waves probed by non-linear transport and noise in the second and third Landau levels

Spontaneous charge ordering is one of the many intriguing quantum phenomena occurring in a 2D electron gas (2DEG) in quantum Hall regime. In the first (N=0) Landau level (LL), the short range attractive part of Coulomb interaction is known to be responsible for the condensation of quasiparticles into an incompressible Laughlin liquid hosting a fractional quantum Hall effect (FQHE) [1] and carrying fractional charges. In higher LLs (N > 2), however, the situation is markedly different as the combination of short-range attractive with long- range repulsive Coulomb interaction leads to electronic phases forming charge density waves (CDWs) [2,3]. In this work, CDWs were investigated in the second and third Landau levels using non-linear electronic transport as well as noise measurements in a Corbino geometry. Unlike traditional geometries such as Hall or Van der Paw geometries, the Corbino geometry offers a direct access to the bulk conductivity 𝜎𝜎𝑥𝑥𝑥𝑥 without any contributions from edge channels [4]. The concomitant mapping of the conductivity versus bias voltage and magnetic field revealed different types of CDWs, such as pinned CDW phases and liquid crystal-like stripe phases. At particular filling fractions both in the second and third Landau levels, narrow band noise reveals sliding transport characteristics under DC bias voltage. This is the typical signature of liquid-crystal like CDWs. These results shed new light on the elusive re-entrant quantum Hall states in the second Landau level, and they show that these are most likely liquid-crystal like CDWs that can coexist with the FQHE [5].