OBSERVATION OF ZEEMAN SPLITTING IN UNIVERSAL CONDUCTANCE FLUCTUATIONS

We provide experimental evidence for a transition from a random-matrix ensemble with broken time-reversal symmetry to an ensemble with parti ally broken spin-rotation symmetry. The transition from a Gaussian uni tary ensemble to the ensemble in which the Zeeman degeneracy of electr ons is lifted is accompanied by a factor of 2 change in 1/f noise fluc tuations measured in a mesoscopic Li wire at low temperature. The magn etic-field scale characterizing the Zeeman crossover is determined by k(B)T, rather than by the Thouless energy.