Strongly anisotropic transport in higher two-dimensional Landau levels

Abstract

Low-temperature, electronic transport in Landau levels N > 1 of a twodimensional electron system is strongly anisotropic. At half-filling of either spin level of each such Landau level the magnetoresistance either collapses to form a deep minimum or is peaked in a sharp maximum, depending on the in-plane current direction. Such anisotropies are absent in the N = 0 and N = 1 Landau level, which are dominated by the states of the fractional quantum Hall effect. The transport anisotropies may be indicative of a new many particle state, which forms exclusively in higher Landau levels.Typeset using REVT E X 1

Competing Quantum Hall Phases in the Second Landau Level in Low Density Limit

“…As the sample temperature is cooled to 16mK, as shown in Fig. 2, unlike in high density samples where the half-filled states at = 9/2, 11/2 … become strongly anisotropic [8,9], here in this low-density sample, they remain more or less isotropic. This isotropic phase at these half Landau level fillings is probably due to a lower melting temperature of the stripe phase in the low electron density limit [25].…”

“…When a high-quality two-dimensional electron system (2DES) is placed in high magnetic fields and cooled to very low temperature, many novel quantum ground states appear, for example, the integer and fractional quantum Hall effect states [1], the composite fermions (CF) Fermi sea state [2,3], the pinned Wigner crystal states [4,5], the stripe and bubble states [6][7][8][9], etc. The fundamental physics underlying these quantum phenomena and the competition among their ground states is the strong electron-electron interactions.…”

An investigation of orientational symmetry-breaking mechanisms in high Landau levels

“…2 demonstrates this improvement in sample A. The minima in the resistance measured along [110] at ν = 9/2 and 11/2 are much deeper, the isotropic re-entrant integer quantized Hall states in the flanks of the Landau levels are much better developed [2,3,21], and additional structure is evident. Nonetheless, these data show clearly that illumination is not an important factor in the origin or orientation of the anisotropic phases of 2D electrons in high Landau levels.…”

“…At lower magnetic fields the higher LLs become occupied, and in the third or higher (N ≥ 2) LL no FQHE states have been observed. Recent experiments have nevertheless uncovered extraordinary transport signatures unique to the high LL regime, pointing to the existence of a new class of many-body states distinct from the incompressible quantum fluids responsible for the FQHE [2,3]. The most striking of these signatures is the rapid development, at very low temperatures, of strong anisotropies in the longitudinal resistance of the 2D electron system.…”

Spin and Charge Ordering in the Quantum Hall Regime

“…These states are therefore also called reentrant integer quantum Hall states (RIQHS). In the case of ≥ 2, these RIQHS occur at elevated temperatures around partial filling factors˜= 1 ⁄4 and˜= 3 ⁄4, whered enotes the filling factor of the highest occupied Landau level branch [95][96][97]. If the electron temperature is low enough, a seamless transition to the IQHE is observable in Fig.…”