Characterization of Ultra Clean Carbon Nanotubes for Surface Acoustic Wave Integration

Integrating surface acoustic waves (SAWs) with carbon nanotubes promises to be a robust platform to study the effects of periodic electric potentials on one-dimensional (1D) electron systems. Suspended single-walled carbon nanotubes (SWCNTs) are perfect examples of exact one-dimensional electron systems with rich transport phenomena ripe for integration with SAWs. In this work, we report on the characterization of ultra-high-quality of SWCNTs and preliminary SAW transducers for integrated experiments. The ultra-high quality of our SWCNTs has exposed subtle warping of graphene’s Dirac bands, leading to inequivalent K and K’ group velocities. In the Fabry-Perot regime, the asymmetric velocities form long-period conductance oscillations versus gate voltage attributed to Sagnac-like quantum interference [1,2]. We also see effects in the shell-filling quantum dot regime as spontaneous doubly degenerate energy levels are inserted periodically between the expected four-fold degenerate energy levels. This effect highlights the presence of a vernier energy scale between the allowed energy levels of a finite-sized ultraclean carbon nanotube [3]. The plethora of rich electronic phenomena present in SWCNT transport, along with the long CNT length and improvements in small SAW wavelength (down to ~200 nm), present a compelling platform to expand the complexities of 1D physics.

[1] Dirnaichner et al, Phys. Rev. Lett. 117, 166804 (2016)

[2] Lotfizadeh et al, Phys. Rev. Lett. 126, 216802 (2021)

[3] Lotfizadeh, Berg et al, Manuscript in Preparation