Influence of electron-phonon coupling on the low-temperature phases of metallic single-wall carbon nanotubes

Abstract

We investigate the effect of electron-phonon coupling on low temperature phases in metallic singlewall carbon nanotubes. We obtain low-temperature phase diagrams of armchair and zigzag type nanotubes with screened interactions with a weak-coupling renormalization group approach. In the absence of electron-phonon coupling, two types of nanotubes have similar phase diagrams. A D-Mott phase or d-wave superconductivity appears when the on-site interaction is dominant, while a charge-density wave or an excitonic insulator phase emerges when the nearest neighbor interaction becomes comparable to the on-site interaction. The electron-phonon coupling, treated by a twocutoff scaling scheme, leads to different behavior in two types of nanotubes. For strong electronphonon interactions, phonon softening is induced and a Peierls insulator phase appears in armchair nanotubes. We find that this softening of phonons may occur for any intraband scattering phonon mode. On the other hand, the effect of electron-phonon coupling is negligible for zigzag nanotubes. The distinct behavior of armchair and zigzag nanotubes against lattice distortion is explained by analysis of the renormalization group equations.

Anomalous isotope effect in iron-based superconductors

“…Due to the retarded nature of the phonon-mediated interactions, the energy dependence must be included. The minimal approach to include both simultaneous and retarded interactions can be accomplished by the step-shape approximation 38–41 as shown in Fig. 1(a),where g i and represent (instantaneous) electronic interactions and (retarded) phonon-mediated ones.…”

Anomalous screening in narrow-gap carbon nanotubes

“…10,11 Ultraclean, narrow-gap NTs may be charged in a controlled and reversible way by means of Coulomb blockade, hosting fascinating many-body states of matter. These include the Luttinger liquid, [12][13][14][15][16][17][18][19] the Wigner crystal, [19][20][21][22][23][24][25] and a correlated insulator understood as either a Mott 26 or an excitonic phase 27 (but Peierls insulators, [28][29][30] topological phases, 31 and hybrid scenarioes [32][33][34] were proposed as well).…”