1∕fflux flow noise due to a coexistence of qualitatively different vortex states

Abstract

We investigate the vortex-motion voltage noise in a hybrid structure consisting of a weak-pinning amorphous Nb 0.7 Ge 0.3 microbridge on top of which a strong-pinning, longitudinal Nb line with a narrow interruption in the middle is added. The Nb part enforces a branching of the applied current, causing a modulation of the current density within the Nb 0.7 Ge 0.3 , where vortex motion induces a voltage. When the Nb 0.7 Ge 0.3 is sufficiently dissipative, the modulation is strong and the vortex dynamics is spatially dependent. Under these circumstances, the distribution function for normal excitations in vortex cores varies considerably over the sample, which results in a coexistence of distinct vortex states spreading from nearly equilibrium to strongly nonequilibrium ones. This leads to a range of characteristic times for the voltage fluctuations and, consequently, to the frequency ͑f͒ dependence of the noise being of 1 / f type. The noise originates in the fluctuations of the vortex-core size around the average set by the nonequilibrium effects in vortex motion.

Thickness dependent transition from the 1T′ to Weyl semimetal phase in ultrathin MoTe2: electrical transport, noise and Raman studies

“…We have used 1/f noise spectroscopy as a function of temperature to look at this suggestion of MIT, as noise spectroscopy has been used recently in VO 2 to examine the MIT [34]. We further note that 1/f noise measurements have been utilized as a sensitive tool to probe structural phase transitions [35,36], vortex flux dynamics near superconductor-normal phase transition [37] and electronic phase transition [38,39]. We will show that our 1/f noise spectra do not agree with this conjecture and propose that it is related to electron-electron interaction physics in the WSM state arising from the current carrying electron-hole states at the Weyl nodes [33].…”

Nonlocal versus local vortex dynamics in the transversal flux transformer effect

“…Strong lateral temperature variations over a-NbGe microbridge films (also on oxidized Si) due to EH at low T were also observed in a noise experiment. 18 This gives an additional support to the reality of spatially dependent separation of the electron temperature T * and the phonon temperature T 0 at least for the given substrate-film interface properties. 19 In Fig.…”