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Abstract Topological insulators possess protected boundary states which are robust against disorders and have immense implications in both fermionic and bosonic systems. Harnessing these topological effects in nonequilibrium scenarios is highly desirable and has led to the development of topological lasers. The topologically protected boundary states usually lie within the bulk bandgap, and selectively exciting them without inducing instability in the bulk modes of bosonic systems is challenging. Here, we consider topological parametrically driven nonlinear resonator arrays that possess complex eigenvalues only in the edge modes in spite of the uniform pumping. We show parametric oscillation occurs in the topological boundary modes of one and two dimensional systems as well as in the corner modes of a higher order topological insulator system. Furthermore, we demonstrate squeezing dynamics below the oscillation threshold, where the quantum properties of the topological edge modes are robust against certain disorders. Our work sheds light on the dynamics of weakly nonlinear topological systems driven out-of-equilibrium and reveals their intriguing behavior in the quantum regime.
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Are microtubules electron-based topological insulators?
Abstract A microtubule is a cylindrical biological polymer that plays key roles in cellular structure, transport, and signalling. In this work, based on studies of electronic properties of polyacetelene and mechanical properties of microtubules themselves (Spakowitz A. J.,Phys. Rev. Lett.,103(2009) 248101), we explore the possibility that microtubules could act as topological insulators that are gapped to electronic excitations in the bulk but possess robust electronic bounds states at the tube ends. Through analyses of structural and electronic properties, we model the microtubule as a cylindrical stack of Su-Schrieffer-Heeger chains (originally proposed in the context of polyacetylene) describing electron hopping between the underlying dimerized tubulin lattice sites. We postulate that the microtubule is mostly uniform, dominated purely by GDP-bound dimers, and is capped by a disordered regime due to the presence of GTP-bound dimers as well. In the uniform region, we identify the electron hopping parameter regime in which the microtubule is a topological insulator. We then show the manner in which these topological features remain robust when the hopping parameters are disordered. We briefly mention possible biological implications for these microtubules to possess topologically robust electronic bound states.
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- Award ID(s):
- 2004825
- PAR ID:
- 10441327
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Europhysics Letters
- Volume:
- 143
- Issue:
- 4
- ISSN:
- 0295-5075
- Format(s):
- Medium: X Size: Article No. 46001
- Size(s):
- Article No. 46001
- Sponsoring Org:
- National Science Foundation
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