Quantum interference between the third and fourth exciton states in semiconducting carbon nanotubes using resonance Raman spectroscopy |
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Authors: | Duque Juan G Telg Hagen Chen Hang Swan Anna K Shreve Andrew P Tu Xiaomin Zheng Ming Doorn Stephen K |
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Institution: | Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. |
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Abstract: | We exploit an energy level crossover effect Haroz et al., Phys. Rev. B 77, 125405 (2008)] to probe quantum interference in the resonance Raman response from carbon nanotube samples highly enriched in the single semiconducting chiralities of (8,6), (9,4), and (10,5). UV Raman excitation profiles of G-band spectra reveal unambiguous signatures of interference between the third and fourth excitonic states (E(33) and E(44)). Both constructive and destructive responses are observed and lead to anomalous intensity ratios in the LO and TO modes. Especially large anomalies for the (10,5) structure result from nearly identical energies found for the two E(ii) transitions. The interference patterns demonstrate that the sign of the exciton-phonon coupling matrix elements changes for the LO mode between the two electronic states, and remains the same for the TO mode. Significant non-Condon contributions to the Raman response are also found. |
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