Abstract
Under the influence of a constant drive the moving vortex state in 2H-NbS2 superconductor exhibits a negative differential resistance (NDR) transition from a steady flow to an immobile state. This state possesses a high depinning current threshold ({{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}) with unconventional depinning characteristics. At currents well above {{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}, the moving vortex state exhibits a multimodal velocity distribution which is characteristic of vortex flow instabilities in the NDR regime. However at lower currents which are just above {{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}, the velocity distribution is non-Gaussian with a tail extending to significant negative velocity values. These unusual negative velocity events correspond to vortices drifting opposite to the driving force direction. We show that this distribution obeys the Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR). Just above {{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}, we also find a high vortex density fluctuating driven state not obeying the conventional GC-NEFR. The GC-NEFR analysis provides a measure of an effective energy scale (Eeff) associated with the driven vortex state. The Eeff corresponds to the average energy dissipated by the fluctuating vortex state above {{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}. We propose the high Eeff value corresponds to the onset of high energy dynamic instabilities in this driven vortex state just above {{boldsymbol{I}}}_{{boldsymbol{c}}}^{{boldsymbol{h}}}.
Highlights
Periodic elastic medium of vortices in type II superconductors driven through a random pinning environment, is haepnocweeirnftuelrp-vroortotetxypsepafocrinsgtuad0y∝ingn−n1o/n2)-eisqucoilnibvreinumien(tNlyEa)nsdysctoenmtsin1–u3.oTuhsleyvvoarrtieexdnbuymchbaenr gdienngsitthye, nm=agBne/φti0c (and field (B), φ0 is the magnetic flux quanta carried by each vortex
This Eeff corresponds to the energy associated with 2.5 μW of power dissipated by the fluctuations in the driven vortex state above Ich over a time interval, tw = 0.1 s, where tw is the average time for a vortex to drift across the sample width (Note 2.5 μW = 49.8 mA × 50 μV, where from P(V) in Recall that both experimental and theoretical studies show that vortex velocities drop to a low, non-zero value at the negative differential resistance (NDR) transition[22,23,24, 26]
We propose generation of dynamic instabilities in the NDR regime ceases vortex flow completely in of significant field oduepr esynsdteenmc.eTohfisIchh,igphreIschenstcaeteoefxvheilboictistyunflcuocntuveantitoionnsaalbdoevpeinIcnh iwnigthpruonpuesrutiaels,nveigza.,ttihvee absence velocity events, the transient time period over which velocity fluctuations are sustained exhibits a critical diverging behaviour of the form τh ∝ 1/ I − Ich β and validity of Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR)
Summary
Periodic elastic medium of vortices in type II superconductors driven through a random pinning environment, is haepnocweeirnftuelrp-vroortotetxypsepafocrinsgtuad0y∝ingn−n1o/n2)-eisqucoilnibvreinumien(tNlyEa)nsdysctoenmtsin1–u3.oTuhsleyvvoarrtieexdnbuymchbaenr gdienngsitthye, nm=agBne/φti0c (and field (B), φ0 is the magnetic flux quanta carried by each vortex. Studies in YNi2B2C crystals[17] and melt spun FexNi1−xZr2 samples[18] have shown that at large driving currents the driven vortex state can enter a high Ic state. A recent study[19] in a single crystal of 2H-NbS2 shows a drive induced abrupt transformation from a moving to an immobile vortex state with a high critical current, Ich. Earlier simulation and experimental studies in high Tc superconductors on negative differential resistance (NDR) transitions have shown that at large drives, dynamical vortex flow instabilities can produce a drop in vortex velocity[20,21,22,23,24,25,26,27]. In this paper using current (I) – voltage (V) and voltage time series measurements we investigate an abrupt transition from a free flow to an immobile vortex state in three different single crystals of 2H-NbS2 with different. We ensured the sample temperature (T) was stable to within 5 mK
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
