Symmetry braking by twinning in misfit layer compounds

Date

Feb 11, 2025

Time

11:00 AM - 12:00 PM

Speaker

Ass. Prof. Klára Uhlirova

Affiliation

Charles University, Faculty of Mathematics and Physics, Department of condensed matter physics, Pra

Language

en

Main Topic

Materialien

Host

Rita Taubert

Description

Misfit layered compounds (MLCs) are thermodynamically stable natural van der Waals superlattices formed by MX and TX layers (where T = Ti, V, Cr or Ta and M = Sn, Sb, Pb or Bi or even rare earth, X = S or Se), alternately stacked along the c-axis. Within the basal plane, the MX and TX2 are incommensurate due to the different lattice parameters of each layer [1]. We present studies of two MLC representatives. The first one is non-polar (PbS)1.11VS2, where we demonstrated for the first time the creation of moiré superstructures in bulk crystal based on natural twinning [2,3]. We showed that twins are grown with preferably 2H or 3R stacking and that those twins have a small twist angle with respect to each other. Such twins have the potential to form a moiré pattern like artificially twisted bilayers made of hBN, graphene or transition metal dichalcogenides [4-6]. In this way, the polar 3R stack leads to sliding-ferroelectric interfaces in the originally nonpolar system [2,3]. The second material, (BiS)1.23CrS2, has a polar structure, and it is, therefore, a sliding-ferroelectric compound in bulk form. Our preliminary studies, including transmission electron microscopy (TEM), indicate that interaction between the ferroelectric domains leads to a regular array of twins with opposite polarization. At the end we would like to discuss the use of natural twinning in magnetic MLCs for engineering materials properties, especially the potential for finding exotic magnetic or multiferroic states.

Links

• Seminars at the IFW

Last modified: Feb 11, 2025, 7:35:32 AM