Transition from turbulent to nearly laminar vortex flow in superconductors with periodic pinning

Abstract

We revisit the vortex dynamics in Al thin films containing an artificial periodic array of antidots by means of electrical transport measurements. We clearly identify a turbulent to laminarlike vortex flow transition which manifests itself as a negative differential resistivity. This transition is accompanied by a strong irreversibility in the voltage-current characteristics. The dynamical phase diagrams obtained as a function of commensurability, temperature, and driving force are in good agreement with the early predictions by Reichhardt et al. ͓Phys. Rev. Lett. 78, 2648 ͑1997͔͒ based on molecular dynamic simulations. DOI: 10.1103/PhysRevB.80.140514 PACS number͑s͒: 74.25.Qt, 74.25.Dw, 74.40.ϩk, 74.78.Na The pioneering work of Giaever 1 provided the first experimental evidence that dc electrical resistance in type-II superconductors is a direct consequence of the motion of Abrikosov vortices.Extensive molecular dynamics ͑MD͒ simulations of array of vortices treated as overdamped objects interacting repulsively with each other and moving over a predefined potential landscape have proven to be a remarkably successful tool to describe the vortex dynamics in all sort of superconductors. 2 Superconductors with a periodic array of pinning centers represent a unique playground to investigate the interaction between vortices and pinning sites. [3][4][5] Early MD simulations for this particular system by Reichhardt et al. 6,7 predicted a remarkable property, namely, the existence of a dynamic transition from a highly dissipative disordered vortex flow at low driving forces to a less dissipative state of ordered flow where pinned vortices coexist with fast solitonlike excitations at higher currents. The sequence in which these dynamical phases appear is highly nontrivial and even counterintuitive since it implies a reduction of the average vortex mobility by increasing the driving force.In spite of the great deal of attention that this fascinating discovery has received in the superconducting community, so far there has been no experimental confirmation of it. A possible cause, recently pointed out by Misko et al.,8,9 is that strong heating or disorder effects can mask this effect. In this Rapid Communication we provide unambiguous experimental evidence that a superconducting film with a periodic array of antidots exhibits a clear turbulent to laminarlike vortex flow transition provided that heat removal is efficient. This transition appears as a negative differential resistivity in the current-voltage characteristics. We demonstrate that the loci of the dynamic transitions in a magnetic field-temperature phase diagram are highly sensitive to the pinning strength and commensurability of the system. At high bias currents the simplified model of a vortex as a pointlike classical particle which ignores the internal structure of the vortex and its elastic nature seems to fail and more realistic approaches, such as time dependent Ginzburg-Landau formalism, become necessary.The investigated sample consists of an Al film of...

Dynamic regimes for driven colloidal particles on a periodic substrate at commensurate and incommensurate fillings

“…These vortex imaging experiments could access only relatively small regions of space, and vortex arrangements at incommensurate fillings were never studied [7]. Under an applied drive, a number of incommensuration and soliton vortex flow states were observed at fillings a few percent above and below f = 1.0 [8]. Simulations at high fillings in these vortex systems produced a variety of dynamical phases [55]; however, experimental observations of these regimes have proven difficult, in part due to the possibility of multiply occupied pinning sites.…”

“…Soliton-type flow for driven particle systems has also been studied for friction models [25][26][27] as well as for vortices in type-II superconductors interacting with periodic pinning arrays, where the soliton flow produces distinct features in the current-voltage curves that are analogs to the velocity-force curves in the driven colloidal systems [8][9][10]47]. Kink motion also occurs in experiments on colloidal particles moving over quasiperiodic substrates [39].…”

“…The type of particle motion that occurs at depinning strongly depends on the filling fraction and on whether the configuration is commensurate or incommensurate. Specific examples of systems that exhibit commensurate-incommensurate depinning transitions include vortices in type-II superconductors interacting with nanostructured periodic pinning arrays [5][6][7][8][9][10], vortices in Bose-Einstein condensates with a co-rotating periodic optical trap array [11], sliding charge density wave systems [12], colloidal particles interacting with periodic substrates [13][14][15][16][17][18][19][20][21][22], and charged metallic balls on patterned surfaces [23]. There are also many models of frictional systems in which a monolayer of atoms is driven over a pinned periodic monolayer of atoms, producing behavior that depends on whether the driven monolayer is commensurate or incommensurate with the underlying pinned layer [24][25][26][27][28][29][30][31].…”

Quantized transport for a skyrmion moving on a two-dimensional periodic substrate

“…At the transitions between locking steps, the net skyrmion velocity V = ( V || 2 + V ⊥ 2 ) 1/2 decreases with increasing external drive F D . This phenomenon is known as negative differential mobility, and it has been observed in other systems where particles are driven over a periodic substrate, such as superconducting vortices moving over periodic pinning arrays where there are transitions between different dynamical phases 43 . Negative differential mobility is also a common feature in semiconductor devices 57 and can be useful for creating logic devices.…”

“…There are other examples of particles moving over ordered substrates, such as vortices in type-II superconductors with periodic pinning arrays [41][42][43] or colloids placed on optically created periodic substrates 44,58 . In these systems the dynamics is overdamped; however, there can be directional locking effects in which the particles preferentially move along symmetry directions of the underlying substrate as the direction of drive is rotated with respect to the substrate lattice [45][46][47][48][49][50][51][52] .…”