295 research outputs found
Current driven magnetization dynamics in ferromagnetic nanowires with Dzyaloshinskii-Moriya interaction
We study current induced magnetization dynamics in a long thin ferromagnetic
wire with Dzyaloshinskii-Moriya interaction (DMI). We find a spiral domain wall
configuration of the magnetization and obtain an analytical expression for the
width of the domain wall as a function of the interaction strengths. Our
findings show that above a certain value of DMI a domain wall configuration
cannot exist in the wire. Below this value we determine the domain wall
dynamics for small currents, and calculate the drift velocity of the domain
wall along the wire. We show that the DMI suppresses the minimum value of
current required to move the domain wall. Depending on its sign, the DMI
increases or decreases the domain wall drift velocity.Comment: 4 pages, 2 figure
Geometrical phases and quantum numbers of solitons in nonlinear sigma-models
Solitons of a nonlinear field interacting with fermions often acquire a
fermionic number or an electric charge if fermions carry a charge. We show how
the same mechanism (chiral anomaly) gives solitons statistical and rotational
properties of fermions. These properties are encoded in a geometrical phase,
i.e., an imaginary part of a Euclidian action for a nonlinear sigma-model. In
the most interesting cases the geometrical phase is non-perturbative and has a
form of an integer-valued theta-term.Comment: 5 pages, no figure
Electric signature of magnetic domain-wall dynamics
We study current-induced domain-wall dynamics in a thin ferromagnetic
nanowire. The domain-wall dynamics is described by simple equations with four
parameters. We propose the procedure to determine these parameters by
all-electric measurements of the time-dependent voltage induced by the
domain-wall motion. We provide an analytical expression for the time variation
of this voltage. Furthermore, we show that the measurement of the proposed
effects is within reach with current experimental techniques.Comment: 5 pages, 5 figures, update to published versio
Minimization of Ohmic losses for domain wall motion in a ferromagnetic nanowire
We study current-induced domain-wall motion in a narrow ferromagnetic wire.
We propose a way to move domain walls with a resonant time-dependent current
which dramatically decreases the Ohmic losses in the wire and allows to drive
the domain wall with higher speed without burning the wire. For any domain wall
velocity we find the time-dependence of the current needed to minimize the
Ohmic losses. Below a critical domain-wall velocity specified by the parameters
of the wire the minimal Ohmic losses are achieved by dc current. Furthermore,
we identify the wire parameters for which the losses reduction from its dc
value is the most dramatic.Comment: 4 pages (+ 4 pages of supplementary material), 4 figure
Holey topological thermoelectrics
We study the thermoelectric properties of three-dimensional topological
insulators with many holes (or pores) in the bulk. We show that at high density
of these holes the thermoelectric figure of merit ZT can be large due to the
contribution of the conducting surfaces and the suppressed phonon thermal
conductivity. The maximum efficiency can be tuned by an induced gap in the
surface states dispersion through tunneling or external magnetic fields. The
large values of ZT, much higher than unity for reasonable parameters, make this
system a strong candidate for applications in heat management of nanodevices,
especially at low temperatures.Comment: 4+ pages, 6 figure
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