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Updated: Jun 3, 2026

Fabricating van der Waals Heterostructures with Precise Rotational Alignment
Published on: July 5, 2019
Rotation-reversal symmetries in crystals and handed structures
Venkatraman Gopalan1, Daniel B Litvin
1Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16803, USA. vgopalan@psu.edu
Abstract:
Symmetry is a powerful framework to perceive and predict the physical world. The structure of materials is described by a combination of rotations, rotation-inversions and translational symmetries. By recognizing the reversal of static structural rotations between clockwise and counterclockwise directions as a distinct symmetry operation, here we show that there are many more structural symmetries than are currently recognized in right- or left-handed helices, spirals, and in antidistorted structures composed equally of rotations of both handedness. For example, we show that many antidistorted perovskites possess twice the number of symmetry elements as conventionally identified. These new 'roto' symmetries predict new forms for 'roto' properties that relate to static rotations, such as rotoelectricity, piezorotation, and rotomagnetism. They enable a symmetry-based search for new phenomena, such as multiferroicity involving a coupling of spins, electric polarization and static rotations. This work is relevant to structure-property relationships in all materials and structures with static rotations.
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