Browsing by Author "Staniforth, Michael"

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Intertube Excitonic Coupling in Nanotube Van der Waals Heterostructures
(2022-03-09) Burdanova, Maria G.; Liu, Ming; Staniforth, Michael; Zheng, Yongjia; Xiang, Rong; Chiashi, Shohei; Anisimov, Anton; Kauppinen, Esko I.; Maruyama, Shigeo; Lloyd-Hughes, James
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Strong intertube excitonic coupling is demonstrated in 1D van der Waals heterostructures by examining the ultrafast response of radial C/BN/MoS2 core/shell/skin nanotubes to femtosecond infrared light pulses. Remarkably, infrared excitation of excitons in the semiconducting carbon nanotubes (CNTs) creates a prominent excitonic response in the visible range from the MoS2 skin, even with infrared photons at energies well below the bandgap of MoS2. Via classical analogies and a quantum model of the light–matter interaction these findings are assigned to intertube excitonic correlations. Dipole–dipole Coulomb interactions in the coherent regime produce intertube biexcitons, which persist for tens of femtoseconds, while on longer timescales (>100 ps) hole tunneling—from the CNT core, through the BN tunnel barrier, to the MoS2 skin—creates intertube excitons. Charge transfer and dipole–dipole interactions thus play prominent roles on different timescales, and establish new possibilities for the multi-functional use of these new nanoscale coaxial cables.
Ultrafast, high modulation depth terahertz modulators based on carbon nanotube thin films
(2021-03) Burdanova, Maria G.; Katyba, Gleb M.; Kashtiban, Reza; Komandin, Gennady A.; Butler-Caddle, Edward; Staniforth, Michael; Mkrtchyan, Aram A.; Krasnikov, Dmitry V.; Gladush, Yuriy G.; Sloan, Jeremy; Nasibulin, Albert G.; Lloyd-Hughes, James
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The development of THz technology and communication systems is creating demand for devices that can modulate THz beams rapidly. Here we report the design and characterisation of high-performance, broadband THz modulators based on the photo-induced transparency of carbon nanotube films. Rather than operating in the standard modulation mode, where optical excitation lowers transmission, this new class of modulators exhibits an inverted modulation mode with an enhanced transmission. Under femtosecond pulsed illumination, modulation depths reaching +80% were obtained simultaneously with modulation speeds of 340 GHz. The influence of the film thickness on the insertion loss, modulation speed and modulation depth was explored over a frequency range from 400 GHz to 2.6 THz. The excellent modulation depth and high modulation speed demonstrated the significant potential of carbon nanotube thin films for ultrafast THz modulators.