MECHANICAL STRAIN, CONDUCTANCE FLUCTUATIONS, AND DYNAMICS OF SINGLE TUNNELING DEFECTS

We have applied mechanical strain to mesoscopic Bi wires, and report s everal new observations, The universal conductance fluctuations (UCF) are quite sensitive to strain: a strain of only 5 x 10(-7) changes the conductance by order e(2)/h at T = 45 mK, suggesting a large shift wi th strain of either the Fermi energy or the positions of some scatteri ng centers. The random telegraph signals associated with two-level sys tems (TLS) vary both in amplitude and switching rate with applied stra in. The amplitude variation is random, consistent with UCF, while the slower transition rate varies monotonically with strain. The energy as ymmetry of the TLS (deduced from the ratio of the transition rates) ha s a linear coupling to strain, with a deformation potential of 2-3 eV.