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Accueil du site > Publications > Publications 2006 > Parity law of the singlet-triplet gap in graphitic ribbons

Parity law of the singlet-triplet gap in graphitic ribbons

Mohamad Al Hajj, Fabien Alet, Sylvain Capponi, Marie-Bernadette Lepetit, Jean-Paul Malrieu and Synge Todo

par Webmaster - 19 novembre 2004

This work explores the possibility to transfer the parity law of the singlet-triplet gap established for square ladders (gapped for even number of legs, gapless for odd number of legs) to fused polyacenic 1-D systems, i.e., graphite ribbons. Qualitative arguments are presented in favor of a gapped character when the number n_{\omega} of benzene rings along the ribbon width is odd. A series of numerical calculations (quantitative mapping on spin 1/2 chains, renormalized excitonic treatments and Quantum Monte Carlo) confirm the parity law and the gapless character of the ribbon for even n_{\omega}.