Topological Metadefects: Tangles of Dislocations.
Pawel Pieranski1, Mehdi Zeghal1, Maria Helena Godinho2
1Université Paris-Saclay, Laboratoire de Physique des Solides, 91405 Orsay, France.
Physical Review Letters
|October 6, 2023
Summary
Researchers introduce topological metadefects, which are defects formed from other defects. These complex structures, observed in cholesterics under strain, exhibit unique formation and interaction rules.
Area of Science:
- Condensed matter physics
- Materials science
- Topology
Background:
- Topological defects are universal phenomena in nature.
- They serve as indicators of symmetry breaking during phase transitions.
- Examples include disclinations, dislocations, and vortices.
Purpose of the Study:
- To introduce the concept of topological metadefects.
- To investigate the formation of these structures in cholesterics.
- To analyze their symmetry breaking and interaction properties.
Main Methods:
- Utilizing dislocation tangles as a model system.
- Applying tensile strain to Lehmann clusters in cholesterics.
- Observing symmetry breaking from D₂ to C₂.
Main Results:
- Generation of dextrogyre and levogyre primary tangles.
- Formation via D₂→C₂ symmetry breaking from Lehmann clusters.
- Primary tangles can form double helices.
- Metadefects exhibit annihilation and associative behaviors with algebraic rules.
Conclusions:
- Topological metadefects represent a novel class of complex defects.
- Their formation is linked to specific symmetry breaking mechanisms.
- These structures follow predictable rules for interaction and evolution.
Related Concept Videos
02:17Microtubule Instability
5.1K
Microtubules are hollow cylindrical filaments having a diameter of approximately 25 nm and a length that varies from 200 nm to 25 μm. GTP-bound tubulin subunits form αβ-heterodimers for microtubule assembly. These core building blocks interact longitudinally, polymerizing into protofilaments. The protofilaments then interact with one another through lateral bonding forces to form stable cylindrical microtubules. These cylindrical filaments are dynamic as they undergo repeated...
5.1K
02:02DNA Topoisomerases
31.4K
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. ...
Types and Mechanism of action
Topoisomerases are divided into two main types. ...
31.4K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
42.8K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
42.8K
01:45Destabilization of Microtubules
2.7K
The destabilization of microtubules can occur during different stages of the microtubule lifecycle, such as nucleation or elongation. It can take place at either end of the microtubule or in the microtubule lattices as a whole. The lifespan of individual microtubules within a cell varies according to the cell type and stage of the cell cycle. During interphase, the lifespan of the microtubule is about 30 minutes, while during cell division, it is about 15 minutes. In axonal microtubules of...
2.7K
02:58Crystal Field Theory - Octahedral Complexes
26.6K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
26.6K
01:21Deformations in a Transverse Cross Section
206
When a material is subjected to uniaxial stress, it elongates or contracts in the direction of the applied force, and also undergoes changes in the perpendicular directions. This behavior is crucial for understanding how materials behave under stress and is governed by mechanical properties such as Poisson's ratio v, which measures the ratio of transverse strain to axial strain.
As the material stretches, it expands or contracts in orthogonal directions to the load. This phenomenon varies...
As the material stretches, it expands or contracts in orthogonal directions to the load. This phenomenon varies...
206