title: Quantum-coupled radial-breathing oscillations in double-walled carbon nanotubes.
abstract: Van der Waals-coupled materials, ranging from multilayers of graphene and MoS(2) to superlattices of nanoparticles, exhibit rich emerging behaviour owing to quantum coupling between individual nanoscale constituents. Double-walled carbon nanotubes provide a model system for studying such quantum coupling mediated by van der Waals interactions, because each constituent single-walled nanotube can have distinctly different physical structures and electronic properties. Here we systematically investigate quantum-coupled radial-breathing mode oscillations in chirality-defined double-walled nanotubes by combining simultaneous structural, electronic and vibrational characterizations on the same individual nanotubes. We show that these radial-breathing oscillations are collective modes characterized by concerted inner- and outer-wall motions, and determine quantitatively the tube-dependent van der Waals potential governing their vibration frequencies. We also observe strong quantum interference between Raman scattering from the inner- and outer-wall excitation pathways, the relative phase of which reveals chirality-dependent excited-state potential energy surface displacement in different nanotubes.
authors: Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
authors: Kaihui
authors: K
authors: Liu
authors: Xiaoping
authors: X
authors: Hong
authors: Muhong
authors: M
authors: Wu
authors: Fajun
authors: F
authors: Xiao
authors: Wenlong
authors: W
authors: Wang
authors: Xuedong
authors: X
authors: Bai
authors: Joel W
authors: JW
authors: Ager
authors: Shaul
authors: S
authors: Aloni
authors: Alex
authors: A
authors: Zettl
authors: Enge
authors: E
authors: Wang
authors: Feng
authors: F
authors: Wang