We study spin-orbit coupling in metallic carbon nanotubes (CNTs) within the many-body Tomonaga-Luttinger liquid (TLL) framework. For a well defined sub-class of metallic CNTs, that contains both achiral zig-zag as well as a sub-set of chiral tubes, a
n effective low energy field theory description is derived. We aim to describe system at finite dopings, but close to the charge neutrality point (commensurability). A new regime is identified where spin-orbit coupling leads to an inverted hierarchy of mini-gaps of bosonic modes. We then add a proximity coupling to a superconducting (SC) substrate and show that the only order parameter that is supported within the novel, spin-orbit induced phase is a topologically trivial s-SC.
We report the magnetic field-dependent far-infrared reflectivity of polycrystalline bismuth. We observe four distinct absorptions that we attribute to magnetoplasmon resonances, which are collective modes of an electron-hole liquid in magnetic field
and become optical and acoustic resonances of the electron-hole system in the small-field limit. The acoustic mode is expected only when the masses of distinct components are very different, which is the case in bismuth. In a polycrystal, where the translational symmetry is broken, a big shift of spectral weight to acoustic plasmon is possible. This enables us to detect an associated plasma edge. Although the polycrystal sample has grains of randomly distributed orientations, our reflectivity results can be explained by invoking only two, clearly distinct, series of resonances. In the limit of zero field, the optical modes of these two series converge onto plasma frequencies measured in monocrystal along the main optical axes.
