Temperature dependence of the "0.7" 2e2/h quasi-plateau in strongly confined quantum point contacts

New results are presented of the "0.7" (2e(2)/h) quasi-plateau of strongly confined point contacts. The strong confinement is obtained by combining shallow etching with metal gate deposition on GaAs/GaAlAs heterostructures. The resulting subband separations are up to 20 meV, and consequently, the quantized conductance is observed up to 30 K, an order of magnitude higher than in conventional split gate devices. Pronounced quasi-plateaus are observed at the lowest conductance steps from 1 to 30 K, where all structures are smeared out thermally. The deviation of the conductance from ideal integer quantization exhibits an activated behavior as a function of temperature with a density-dependent activation temperature around of 2 K. Our results are analyzed in terms of a model involving scattering against plasmons in the constriction. (C) 1998 Elsevier Science B.V. All rights reserved.