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Solitons in a quasi-one dimensional chain with spin one

Dr. Dario Bercioux (Donostia International Physics Center)

Place: Sala 0.7
Time: 15.3.2017, 11:00
Title: Solitons in a quasi-one dimensional chain with spin one

In this talk I will revise the physics of the Su-Schrieffer-Heeger (SSH) model [1]. This is a minimal one-dimensional tight-binding model introduced more than 30 years ago for explaining the presence of solitons in conjugated polymers. This model is characterized by two distinct topological phases marked by different winding numbers of the eigenstates. Topological phases are observed both as end chain state or as domain-wall at defects. Historically, the topologically protected domain-wall states in the SSH model provide a condensed-matter realization of the domain-wall states in the Jackiw-Rebbi model of (1+1)-dimensional Dirac equation with a mass kink [2].

We present an extension of the SSH model to a quasi-one-dimensional system characterized by an underlying Hamiltonian with integer spin [3,4]. We investigate the spectral properties of a quasi-one-dimensional lattice in two possible dimerisation configurations. Both configurations are characterised by the same lattice topology and the identical spectra containing a flat band at zero energy. We find that, one of the dimerised configuration has similar symmetry to the SSH model. Whereas, the other dimerised configuration only shows non-trivial topological properties in the presence of chiral-symmetry breaking adiabatic pumping [5].

[1] W. P. Su, J. R. Schrieffer, & A. J. Heeger Phys. Rev. Lett. 42, 1698 (1979).
[2] R. Jackiw & C. Rebbi Phys. Rev. D 13, 3398 (1976).
[3] D. Bercioux, M. Governale, V. Cataudella, & V. M. Ramaglia Phys. Rev. Lett. 93, 056802 (2004).
[4] D. Bercioux, O. Dutta, & E. Rico, arXiv:1609.06292, to appear in Ann. Phys. (Berlin).
[5] D. Meidan, T. Micklitz, & P. W. Brouwer Phys. Rev. B 84, 195410 (2011).