Regensburg 2016 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Spintronics (incl. quantum dynamics) (Joint session of HL, MA and TT, organized by MA)

HL 52.9: Talk

Wednesday, March 9, 2016, 11:45–12:00, H32

Dynamics of bound monopoles in artificial spin ice: How to store energy in Dirac strings. — •Elena Vedmedenko — University of Hamburg, Hamburg, Germany

Dirac strings in spin-ices are lines of reversed dipoles joining two quasi-particle excitations. These excitations behave themselves as unbound emergent monopoles if the tension of Dirac strings vanishes. In this work analytical and numerical analysis are used to study dynamics of two-dimensional dipolar spin ices, artificially created analogs of bulk spin-ice, in the regime of bound monopoles. It is shown that in this regime strings rather than monopoles are effective degrees of freedom explaining the finite-width band of Pauling states. A measurable prediction of path-time dependence of endpoints of stretched and then released Dirac string is made and verified via simulations. It is shown that string dynamics is defined by the characteristic tension-to-mass ratio, which is determined by the fine structure constant and lattice dependent parameter. It is proposed to use string tension to achieve spontaneous magnetic currents. A concept of energy storing device on the basis of this principle is proposed and illustrated by an experimental demonstration. A scheme of independent measurement at the nanoscale is proposed.