Korringa-like nuclear spin–lattice relaxation in a 2DES at ν=1/2

Abstract

Via a resistively detected NMR technique, the nuclear spin–lattice relaxation time T_1 of ^(71)Ga has been measured in a GaAs/AlGaAs heterostructure containing two weakly coupled 2D electron systems (2DES) at low temperatures, each at Landau level filling v=1/2. Incomplete electronic spin polarization, which has been reported previously for low density 2DESs at v=1/2, should facilitate hyperfine-coupled nuclear spin relaxation owing to the presence of both electron spin states at the Fermi level. Composite fermion theory suggests a Korringa-law temperature dependence: T_1T = constant is expected for temperatures T<1K. Our measurements show that for temperatures in the range 35mK

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