Institute for Soft Matter Synthesis and Metrology

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Rameswar Bhattacharjee and Miklos Kertesz have introduced a novel approach to characterize the topological phases of several well-known π-conjugated polymers. Their work, published in the Journal of the American Chemical Society, focuses on the role of edge states in determining the topological phase of these materials.

The presence or absence of edge states is directly related to whether the polymers exhibit non-trivial or trivial topological phases, often quantified by the Zak invariant, also known as the Z₂-value. A Z₂ value of 1 indicates a non-trivial topological insulator, while a value of 0 corresponds to a trivial phase. The researchers discovered that the topological nature of π-conjugated polymers is intrinsic, with 15 polymers identified as trivial and 9 classified as non-trivial. Moreover, they demonstrated that applying a continuous external perturbation, such as mechanical strain, can alter the topological phases of these polymers. The polymer’s response to such strain is characterized by a new parameter defined as the figure of merit, m(ε).