Blowing polar skyrmion bubbles in oxide superlattices

Abstract

Particle-like topological structures such as skyrmions and vortices have garnered everincreasing interests due to the rich physical insights and potential broad applications. Here we discover the reversible switching between polar skyrmion bubbles and ordered vortex arrays in ferroelectric superlattices under an electric field, reminiscent of the Plateau-Raleigh instability in fluid mechanics. Electric field phase diagram is constructed, showing wide stability window for the observed polar skyrmions. This study is a demonstration for the computational design of ferroelectric topological structures and field-induced topological phase transitions.

Atomic imaging of mechanically induced topological transition of ferroelectric vortices

“…Once the core is broken, the entire vortex is quenched quickly within 150 ms. This behavior is different from that proposed in previous theoretical work 30 , whereby vortices were predicted to move and melt to reduce the electrostatic energy under an electric field. In contrast, in our case, the compressive out-of-plane stress drives the rotation of polarization toward 11 the in-plane direction, leading to a reduction in the elastic energy.…”

Polar Morphologies from First Principles: PbTiO3Films on SrTiO3Substrates and the p(2×Λ) Surface Reconstruction

“…We suggest that the MSSF method implemented within the CONQUEST code can now be used to solve a plethora of problems within the perovskite oxides. This could include the simulating other potentially possible polar morphologies in the PTO/STO system such as skyrmion phases [ 14,16 ] and disclinations. [ 13 ] The former has recently been observed in the PTO/STO superlattice [ 16 ] supported by phase‐field and second‐principles simulations.…”

“…These include enhanced colossal magnetoresistance, [ 3 ] high‐temperature superconductivity, [ 4 ] the formation of interfacial 2D electron and hole gases (2DEG/HG), [ 5,6 ] and the emergence of negative capacitance. [ 7 ] While these are becoming well‐documented, [ 8–10 ] new emergent phenomena resulting from exotic electrical polarization textures, including polar waves, vortices, and polar skyrmion phases [ 11–16 ] are less well understood. The toroidal moment born from the chirality of these polar morphologies can give rise to strong electrotoroidic, pyrotoroidic, and piezotoroidic effects [ 13,17,18 ] all of which show promise to be exploited in new low‐dimensional functional devices.…”

Controlling polar-toroidal multi-order states in twisted ferroelectric nanowires

“…More recently, PTMO states have come into focus for their potential in developing multi-state functional devices and the possibility of discovering ferroelectric skyrmion state. 16,23 PTMO states have been theoretically predicted in several specific ferroelectric systems. A particular kind of systems are composite structures which consist of polar components and toroidal components like nanodots embedded in a polar matrix, 24 and ferroelectric film-dot system.…”

“…25 The second kind of systems are particular nanosystems made of rhombohedral phase ferroelectrics and under anisotropic screening condition, such as BaTiO 3 and BaTiO 3 /SrTiO 3 composite nanowires. [14][15][16]23 The most important feature of a PTMO state is the coexistence and possible coupling between the polar order and toroidal order, which gives rise to the distinguished behaviors of a PTMO state compared with purely toroidal or polar state. For example, as a result of the polar-toroidal coupling, superior piezoelectric and piezotoroidal responses 15 and interesting dynamical characteristics 26 are found in PTMO states.…”