Velocity-force characteristics of a driven interface in a disordered medium

Abstract

Using a dynamic functional renormalization group treatment of driven elastic interfaces in a disordered medium, we investigate several aspects of the creep-type motion induced by external forces below the depinning threshold fc: i) We show that in the experimentally important regime of forces slightly below fc the velocity obeys an Arrhenius-type law v ∼ exp[−U (f )/T ] with an effective energy barrier U (f ) ∝ (fc − f ) vanishing linearly when f approaches the threshold fc. ii) Thermal fluctuations soften the pinning landscape at high temperatures. Determining the corresponding velocity-force characteristics at low driving forces for internal dimensions d = 1, 2 (strings and interfaces) we find a particular non-Arrhenius type creep v ∼ exp[−(fc(T )/f ) µ ] involving the reduced threshold force fc(T ) alone. For d = 3 we obtain a similar v-f characteristic which is, however, non-universal and depends explicitly on the microscopic cutoff.

Interplay between collective pinning and artificial defects on domain wall propagation in Co/Pt multilayers

“…Figure 3(a) shows several v(H) curves measured at different temperatures in the range 100 K to 300K. The typical collective pinning behavior of a 1D wall propagating in a 2D disordered medium [21] is given by the creep law…”

Marginal pinning of vortices at high temperature

“…Also, the typical barriers separating adjacent valleys are reduced by thermal fluctuations leading to a peculiar form of the creep-type dynamics under a small external force. 11 Below we first discuss some general properties of vortex pinning in disordered type-II superconductors and derive the asymptotic form ͑3͒ of the correlator. Second, we calculate the pinning length L c (T) using the functional renormalization-group ͑FRG͒ approach.…”

“…Furthermore, since we want to study high temperatures, we choose the roughness exponent to take the thermal value ϭ th ϭ1/2 which is convenient since the physics appears more transparently in the sequel, in particular, the temperature does not renormalize when ϭ th and T l ϭT ͑however, note that from a mathematical point of view the physical results below are independent of this particular choice of ). The linearized flow equation can be solved explicitly 11 with the result…”

Depinning and Creep Motion in Glass States of Flux Lines

“…It is observed in our simulations that the system with weak bare pinning strength experiences smaller energy barriers compared with that of strong bare pinning strength, even at the same relative force-deviation from the critical values; an analytic derivation of the effective energy barrier, however, is not an easy task [12]. While a full picture remains to be developed, we notice that, first, vortex motions mimic nucleation processes in first-order phase transitions: the weak (strong) pinning case corresponds to system located at the spinodal (coexistence) curve [31]; second, under weak and strong pinning, vortices behave similarly to CDW [22] and domain wall [27] respectively, due to the different ranges of correlation.…”