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Register a new userNarrow waveguide based on ferroelectric domain wall
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Ferroelectric materials are spontaneous symmetry breaking systems characterized by ordered electric polarizations. Similar to its ferromagnetic counterpart, a ferroelectric domain wall can be regarded as a soft interface separating two different ferroelectric domains. Here we show that two bound state excitations of electric polarization (polar wave), or the vibration and breathing modes, can be hosted and propagate within the ferroelectric domain wall. Specially, the vibration polar wave has zero frequency gap, thus is constricted deeply inside ferroelectric domain wall, and can propagate even in the presence of local pinnings. The ferroelectric domain wall waveguide as demonstrated here, offers new paradigm in developing ferroelectric information processing units.
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Controlling magnetism using voltage is highly desired for applications, but remains challenging due to fundamental contradiction between polarity and magnetism. Here we propose a mechanism to manipulate magnetic domain walls in ferrimagnetic or ferromagnetic multiferroics using electric field. Different from those studies based on static domain-level couplings, here the magnetoelectric coupling relies on the collaborative spin dynamics around domain walls. Accompanying the reversal of spin chirality driven by polarization switching, a rolling-downhill-like motion of domain wall is achieved at the nanoscale, which tunes the magnetization locally. Our mechanism opens an alternative route to pursuit practical and fast converse magnetoelectric functions via spin dynamics.
Using multiscaling analysis, we compare the characteristic roughening of ferroelectric domain walls in PZT thin films with numerical simulations of weakly pinned one-dimensional interfaces. Although at length scales up to a length scale greater or equal to 5 microns the ferroelectric domain walls behave similarly to the numerical interfaces, showing a simple mono-affine scaling (with a well-defined roughness exponent), we demonstrate more complex scaling at higher length scales, making the walls globally multi-affine (varying roughness exponent at different observation length scales). The dominant contributions to this multi-affine scaling appear to be very localized variations in the disorder potential, possibly related to dislocation defects present in the substrate.
Modulating the polarization of a beam of quantum particles is a powerful method to tailor the macroscopic properties of the ensuing energy flux as it directly influences the way in which its quantum constituents interact with other particles, waves or continuum media. Practical polarizers, being well developed for electric and electromagnetic energy, have not been proposed to date for heat fluxes carried by phonons. Here we report on atomistic phonon transport calculations demonstrating that ferroelectric domain walls can operate as phonon polarizers when a heat flux pierces them. Our simulations for representative ferroelectric perovskite PbTiO$_3$ show that the structural inhomogeneity associated to the domain walls strongly suppresses transverse phonons, while longitudinally polarized modes can travel through multiple walls in series largely ignoring their presence.
While an ideal antiparallel ferroelectric wall is considered a unit cell in width (~0.5nm), we show using phase field modeling that the threshold field for moving this wall dramatically drops by 2-3 orders of magnitude if the wall were diffuse by only ~2-3nm. Since antiparallel domain walls are symmetry allowed in all ferroelectrics, and since domain wall broadening on nanometer scale is widely reported in literature, this mechanism is generally applicable to all ferroelectrics.
We have investigated the domain wall resistance for two types of domain walls in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive intrinsic DWR is inferred for domain walls that are pinned at an etching step, which is quite consistent with earlier observations. However, much lower intrinsic domain wall resistance is obtained when domain walls are formed by pinning lines in unetched material. This indicates that the spin transport across a domain wall is strongly influenced by the nature of the pinning.
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