Tuning of non-uniform switch toughening in ferroelectric composites by an electric field

This paper deals with a mode III interfacial crack subject to anti-plane stress and in-plane electric fields. The analysis concentrates on the tuning of fracture toughness from non-uniform ferroelectric-ferroelastic domain switching by an electric field. The electric loading changes the size of the asymmetric switching zone. Employing the weight function method, we obtain the electrically-dependent switch toughening for stationary and quasi-static growing interfacial cracks, respectively. Multi-domain solutions are derived for non-poled and fully-poled ferroelectric composites. Numerical results are presented on the electric field tuning of the critical applied stress intensity factor. The research provides ways to optimize fracture properties of ferroelectric composites by altering the electric field.

Emergence of correlations in twisted monolayer-trilayer graphene heterostructures

Twisted bilayer graphene heterostructures have recently emerged as a well-established platform for studying strongly correlated phases,such as correlated insulating,superconducting,and topological states.Extending this notion to twisted multilayer graphene heterostructures has exhibited more diverse correlated phases,as some fundamental properties related to symmetry and band structures are correspondingly modified.Here,we report the observations of correlated states in twisted monolayer-trilayer(Bernal stacked)graphene heterostructures.Correlated phases at integer fillings of the moire unit cell are revealed at a high displacement field and stabilized with a moderate magnetic field on the electron-doping side at a twist angle of 1.45°,where the lift of degeneracy at the integer fillings is observed in the Landau fan diagram.Our results demonstrate the effectiveness of moire engineering in an extended structure and provide insights into electric-field tunable correlated phases.

Electro-lubrication in Janus transition metal dichalcogenide bilayers

Lubrication induced by a vertical electric field or bias voltage is typically not applicable to twodimensional(2D)van der Waals(vdW)crystals.By performing extensive first-principles calculations,we reveal that the interlayer friction and shear resistance of Janus transition metal dichalcogenide(TMD)MoXY(X/Y=S,Se,or Te,and X≠Y)bilayers under a constant normal force mode can be reduced by applying vertical electric fields.The maximum interlayer sliding energy barriers between AA and AB stacking of bilayers MoSTe,MoSeTe,and MoSSe decrease as the positive electric field increases because of the more significant counteracting effect from the electric field energy and the more significant enhancement in interlayer charge transfer in AA stacking.Meanwhile,the presence of negative electric fields decreases the interlayer friction of bilayer MoSTe,because the electronegativity difference between Te and S atoms reduces the interfacial atom charge differences between AA and AB stacking.These results reveal an electro-lubrication mechanism for the heterogeneous interfaces of 2D Janus TMDs.