Majorana quasiparticles and topological phases in 3D active nematics

• 成果类型: Article
• 署名作者: Head, Louise C.; Negro, Giuseppe; Carenza, Livio N.; Johnson, Nathan; Keogh, Ryan R.; Gonnella, Giuseppe; Morozov, Alexander; Orlandini, Enzo; Shendruk, Tyler N.; Tiribocchi, Adriano; Marenduzzo, Davide
• 署名单位: University of Edinburgh; Koc University; Universita degli Studi di Bari Aldo Moro; Istituto Nazionale di Fisica Nucleare (INFN); University of Padua; Istituto Nazionale di Fisica Nucleare (INFN); Consiglio Nazionale delle Ricerche (CNR)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10176
• DOI: 10.1073/pnas.2405304121
• 发表日期: 2024-12-24
• 关键词: dynamics

摘要

Quasiparticles are low-energy excitations with important roles in condensed matter physics. An intriguing example is provided by Majorana quasiparticles, which are equivalent to their antiparticles. Despite being implicated in neutrino oscillations and topological superconductivity, their experimental realizations remain very rare. Here, we propose a purely classical realization of Majorana fermions in terms of three-dimensional disclination lines in active nematics. The underlying reason is the well-known equivalence, in 3D, between a + 1 / 2 local defect profile and a - 1 / 2 profile, which acts as its antiparticle. The mapping also requires proving that defect profiles transform as spinors, and activity is needed to overcome the elastic cost associated with these excitations, so they spontaneously appear in steady state. We combine topological considerations and numerics to show that active nematics under confinement spontaneously create in their interior topologically charged disclination lines and loops, akin to Majorana quasiparticles with finite momentum. Within a long channel, the phenomenology we observe resembles that of the Kitaev chain, as Majorana-like states appear near the boundaries, while a delocalized topological excitation arises in the form of a chiral disclination line. The analogy between 3D nematic defects and topological quasiparticles further suggests that active turbulence can be viewed as a topological phase, where defects percolate to form delocalized topological quasiparticles similar to those observed in the channel. We propose that three-dimensional active disclinations can be used to probe the physics of Majorana spinors at much larger scale than that for which they were originally introduced, potentially facilitating their experimental study.