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Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

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Effective Topological Charge Cancelation Mechanism.

Luka Mesarec¹, Wojciech Góźdź², Aleš Iglič¹

¹Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, 1000 Ljubljana, Slovenia.

Scientific Reports

|June 3, 2016

Summary

Topological defects (TDs) form during phase transitions. A new mechanism, Effective Topological Charge Cancellation, controls TD positioning and pairing on curved surfaces, crucial for materials science and technology.

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Area of Science:

Soft Matter Physics
Materials Science
Topology

Background:

Topological defects (TDs) are universal features of continuous symmetry breaking phase transitions.
Their properties are independent of microscopic details, impacting material properties and technological applications.
Controlling TD positioning and number is of significant interest.

Purpose of the Study:

To investigate mechanisms controlling the positioning and local number of TDs in 2D soft films.
To introduce and analyze the Effective Topological Charge Cancellation (ETCC) mechanism.
To understand TD behavior on curved surfaces and in the presence of impurities.

Main Methods:

Numerical study of TDs in effectively 2D closed soft films with in-plane orientational ordering.
Definition of an effective topological charge (Δm_eff) incorporating curvature.
Analysis of TD pairing using an electrostatic analogy.

Main Results:

Demonstrated a strong tendency for Δm_eff to approach zero on surfaces with varying Gaussian curvature.
Identified the ETCC mechanism controlling localized assembly and pair formation of TDs.
Estimated a critical depinning threshold for {defect, antidefect} pair formation when Δm_eff is non-zero.

Conclusions:

The ETCC mechanism provides a robust method for controlling topological defects in soft materials.
Curvature and impurities significantly influence TD behavior and pair formation.
Findings have implications for designing materials with tailored properties and for technological applications.