257 research outputs found
Thin-Film Magnetization Dynamics on the Surface of a Topological Insulator
We theoretically study the magnetization dynamics of a thin ferromagnetic
film exchange-coupled with a surface of a strong three-dimensional topological
insulator. We focus on the role of electronic zero modes imprinted by domain
walls (DW's) or other topological textures in the magnetic film.
Thermodynamically reciprocal hydrodynamic equations of motion are derived for
the DW responding to electronic spin torques, on the one hand, and fictitious
electromotive forces in the electronic chiral mode fomented by the DW, on the
other. An experimental realization illustrating this physics is proposed based
on a ferromagnetic strip, which cuts the topological insulator surface into two
gapless regions. In the presence of a ferromagnetic DW, a chiral mode
transverse to the magnetic strip acts as a dissipative interconnect, which is
itself a dynamic object that controls (and, inversely, responds to) the
magnetization dynamics.Comment: 7 pages, 2 figure
Exploiting Coherence in Nonlinear Spin-Superfluid Transport
We show how the interference between superfluid spin currents can endow spin
circuits with coherent logic functionality. While the hydrodynamic aspects of
the linear-response collective spin transport obviate interference features, we
focus on the nonlinear regime, where the critical supercurrent is sensitive to
the phase accumulated by the condensate in a loop geometry. We propose to
control this phase by electrical gating, tuning the spin-condensate coherence
length. The nonlinear aspects of the spin superfluidity thus naturally lend
themselves to the construction of logic gates, uniquely exploiting the
coherence of collective spin currents. Vice versa, this functionality can be
used to reveal the fundamental properties of spin superfluids.Comment: 6 pages, 3 figure
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