"Carbon nanotubes as excitonic insulators"Who: Dr. Massimo Rontani, CnrNano, Modena, Italy Place: Donostia International Physics Center Date: Monday, 17 July 2017, 15:00 Carbon nanotubes as excitonic insulators
Daniele Varsano^{1}, Sandro Sorella^{2}, Davide Sangalli^{3}, Matteo Barborini^{1}, Stefano Corni^{1}, Elisa Molinari^{1,4}, and Massimo Rontani^{1} ^{ } ^{1}CnrNano, Modena, Italy ^{2}SISSA & CnrIom Democritos, Trieste, Italy ^{3}CnrIsm, Roma, Italy ^{4}FIM, University of Modena, Modena, Italy
Fifty years ago Walter Kohn speculated [1] that a zerogap semiconductor might be unstable against the spontaneous generation of excitons?electronhole pairs bound together by Coulomb attraction. The reconstructed ground state would then open a gap breaking the symmetry of the underlying lattice, a genuine consequence of electronic correlations. Here we show [2] that this 'excitonic insulator' is realized in zerogap armchair carbon nanotubes by performing firstprinciples calculations through manybody perturbation theory as well as quantum Monte Carlo. The excitonic order modulates the charge between the two carbon sublattices opening an experimentally observable gap, which scales as the inverse of the tube radius and weakly depends on the axial magnetic field. Our findings confute the Luttinger liquid paradigm for nanotubes and provide tests to experimentally discriminate between excitonic and Mott insulator.
References [1] D. Sherrington and W. Kohn, Rev. Mod. Phys. 40, 767 (1968). [2] D. Varsano, S. Sorella, D. Sangalli, M. Barborini, S. Corni, E. Molinari, and M. Rontani, arXiv:1703.09235.
