Condensed Matter Seminar Series

Possibility for Exciton Bose-Einstein Condensation in Individual Carbon Nanotubes

Igor Bondarev

NC Central University

Thursday May 9,  11:00 am,  Room 298,  Physics Building

Abstract:  I will tell about an interesting possibility that we have recently theoretically demonstrated: 1D exciton Bose-Einstein condensation (BEC)  in individual small-diameter (∼1−2 nm) semiconducting carbon nanotubes (CNs) [1]. This originates from the strong coupling of excitons and low-energy inter-band plasmons enabled via the quantum confined Stark effect by using an external electrostatic field applied perpendicular to the CN axis. The perpendicular electrostatic field mixes excitons and inter-band plasmons of the same band, to result in strongly coupled hybridized excitations ― exciton-plasmons in one individual CN [2]. Such hybridized excitations are strongly correlated collective Bose-type quasi-particles and, therefore, could likely be condensed under appropriately created external conditions ― in spite of the well-known statements of the BEC impossibility in ideal 1D/2D systems and experimental evidence reported earlier for no exciton BEC effect in CNs. Possibilities for achieving BEC in 1D/2D systems were theoretically demonstrated earlier in the presence of an extra confinement potential, and we show that the correlated exciton-plasmon system in a CN presents such a special case. We find the critical BEC temperature and the exciton condensate fraction as functions of the temperature and electrostatic field applied. The effect requires fields ∼1 V/nm and temperatures below 100 K.

[1] I.V.Bondarev and A.V.Meliksetyan, E-print: arXiv1304.2804, 9 Apr 2013.
[2] I.V.Bondarev, Phys. Rev. B 85, 035448 (2012).