Low temperature electronic transports in the presence of a density gradient

• Published in: Solid state communications 2006-10, Vol.140 (2), p.88-93
• Main Authors: Pan, W., Xia, J.S., Stormer, H.L., Tsui, D.C., Vicente, C.L., Adams, E.D., Sullivan, N.S., Pfeiffer, L.N., Baldwin, K.W., West, K.W.
• Format: Article
• Language: English
• Subjects: D. Density gradient; D. Linear magnetoresistance; D. Quantum Hall effect; D. Resistivity rule
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2006.05.048

In this paper, we review low temperature electronic transport results in high quality two-dimensional electron systems. We discuss the quantization of the diagonal resistance, R x x , at the edges of several quantum Hall states. Each quantized R x x value turns out to be close to the difference between the two adjacent Hall plateaus in the off-diagonal resistance, R x y . Moreover, peaks in R x x occur at different positions in positive and negative magnetic fields. All three R x x features can be explained quantitatively by a ∼1% cm electron density gradient. Furthermore, based on this observation, the well known but still enigmatic resistivity rule, relating R x x to d R x y / d B , finds a simple interpretation in terms of this gradient. In another sample, at 1.2 K, R x x we observe a strongly linear magnetic field dependence. Surprisingly, this linear magnetoresistance also originates from the density gradient. Our findings throw an unexpected light on the relationship between the experimentally measured R x x and the diagonal resistivity ρ x x .