arXiv subjects

Allison W. Teixeira

Publications and source records attributed to Allison W. Teixeira.

5 recordsLinked to original sources

arXiv2024

Liquid crystal skyrmions as elastic multipoles

Solitons in liquid crystals are spatially localised stable configuration of the liquid crystal orientational order parameter that exhibit emergent particle-like properties such as mutual interaction, translational motion and reconfigurable self-asembling behaviour in oscillating electric fields. Understanding solitons' out-of-equilibrium interactions remains a significant challenge. In this study, we present a minimalist model capable to address this challenge. We derive analytically elastic multipole interaction potentials between two solitons assuming two dimensional LC configurations. We determine the soliton's elastic dipole and quadrupole moments based on the equilibrium director textures obtained as minimizers of the Frank-Oseen free energy functional. Incorporating the time dependence of the soliton's multipole moments in response to electric field oscillations, we carry out particle-based simulations that demonstrate the formation of soliton chains and two dimensional clusters by varying the amplitude and/or the frequency of the electric field, in agreement with experiments. The presented formalism may serve as a benchmark model for future theoretical developments incorporating, e.g. higher order elastic multipoles or/and many body interactions.

cond-mat.soft↗

arXiv2023

Particle-based model of active skyrmions

Motivated by recent experimental results that reveal rich collective dynamics of thousands-to-millions of active liquid crystal skyrmions we have developed a coarse grained particle-based model of the dynamics of skyrmions in dilute regime. The basic physical mechanism of the skyrmion motion is related to the non-reciprocal rotational dynamics of the liquid crystal director field when the electric field is turned {\it on} and {\it off}. Guided by fine grained results of the Frank-Oseen continuum approach, we have mapped this non-reciprocal director distortions onto an effective force acting asymmetrically upon switching the electrical field {\it on} or {\it off}. The coarse grained model correctly reproduces the skyrmion dynamics, including the velocity reversal as a function of the frequency of a pulse width modulated driving voltage. We have also obtained approximate analytical expressions for the phenomenological model parameters encoding their dependence upon the cholesteric pitch and the strength of the electric field. This has been achieved by fitting coarse grained skyrmion trajectories to those determined in the framework of the Frank-Oseen model.

cond-mat.soft↗

arXiv2021

Manipulating the shape of flexible magnetoelastic nanodiscs with meron-like magnetic states

The control of the magnetic properties of shapeable devices and the manipulation of flexible structures by external magnetic fields is a keystone of future magnetoelectronics-based devices. This work studies the elastic properties of a magnetoelastic nanodisc that hosts a meron as the magnetic state and can be deformed from structures with positive to negative Gaussian curvature. We show that the winding number of the hosted meron is crucial to determine the curvature sign of the stable obtained shape. Additionally, we show that the optimum curvature reached by the nanodisc depends on geometrical and mechanical parameters. It is shown that an increase in the external radius, thickness, and Young's modulus lead to a decrease in the optimum curvature absolute value. Finally, it is shown that the nanodisc's shape also depends on the connection between the polarity and chirality of the vortex-like meron.

physics.class-ph↗

arXiv2020

Motion-induced inertial effects and topological phase transitions in skyrmion transport

In this work, the current-induced inertial effects on skyrmions hosted in ferromagnetic systems are studied. {When the dynamics is considered beyond the particle-like description, magnetic skyrmions can deform due to a self-induced field. We perform Monte Carlo simulations to characterize the deformation of the skyrmion during its movement}. In the low-velocity regime, the deformation in the skyrmion shape is quantified by an effective inertial mass, which is related to the dissipative force. When skyrmions move faster, the large self-induced deformation triggers topological transitions. The transition is characterized by the proliferation of skyrmions and different total topological charge, which are obtained in terms of the skyrmion velocity. Our findings provide an alternative way to describe the skyrmion dynamics that take into account the deformations of its structure. Furthermore, the motion-induced topological phase transition brings the possibility to control the number of ferromagnetic skyrmions by velocity effects.

cond-mat.mes-hall↗

arXiv2020

Effective Potential for Emergent Majorana Fermions in Superconductor Systems

Majorana fermions cannot be found in nature as a free fundamental particle. Nevertheless, in condensed matter systems, they can emerge as a collective excitation. In this work, using functional integration techniques, we calculated the effective potential for emergent Majorana fermions in the Kitaev chain. In this case, we have shown how the superconductor parameter behaves as a function of temperature. Furthermore, we considered surface-induced superconductivity in a Topological Insulator and calculated the effective potential for emergent Majorana fermions in this system. In the case of an s-wave superconductor, we obtained a gap equation equivalent to that one appearing in a quasi-two-dimensional Dirac electronic system, a candidate to explain high-Tc superconductivity. Finally, for the p-wave superconductor, we have obtained a critical value of the electronelectron interaction in the surface of the Topological Insulator, determining the existence or not of induced superconductivity, a remarkable result to guide experiments

cond-mat.str-el↗