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First-principles prediction of high-temperature superconductivity in stretched carbon nanotubes

Hua-Zhen Li, Xun-Wang Yan

Abstract

Superconductivity in quasi-one-dimensional systems is an significant but undervalued research field. In this work, based on the electron-phonon coupling mechanism, we systematically investigate the superconductivity in quasi-one-dimensional carbon nanotube under uniaxial tensile strain. The calculated superconducting critical temperature attains its peak value of 162 K at a uniaxial tensile strain of 4.5\%, being drastically higher than the counterpart in the unstrained carbon nanotube. An overall softening of phonons, strong electron-phonon coupling, and an increase of electronic density of states at the Fermi level, play key roles in achieving high-temperature superconductivity in this system. Our research demonstrates that stretching is an effective approach to modulating the superconductivity one-dimensional materials, and more importantly, indicates that high-temperature superconductivity may occur in carbon nanotubes.

First-principles prediction of high-temperature superconductivity in stretched carbon nanotubes

Abstract

Superconductivity in quasi-one-dimensional systems is an significant but undervalued research field. In this work, based on the electron-phonon coupling mechanism, we systematically investigate the superconductivity in quasi-one-dimensional carbon nanotube under uniaxial tensile strain. The calculated superconducting critical temperature attains its peak value of 162 K at a uniaxial tensile strain of 4.5\%, being drastically higher than the counterpart in the unstrained carbon nanotube. An overall softening of phonons, strong electron-phonon coupling, and an increase of electronic density of states at the Fermi level, play key roles in achieving high-temperature superconductivity in this system. Our research demonstrates that stretching is an effective approach to modulating the superconductivity one-dimensional materials, and more importantly, indicates that high-temperature superconductivity may occur in carbon nanotubes.
Paper Structure (8 sections, 10 equations, 4 figures, 2 tables)

This paper contains 8 sections, 10 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Computational Methods
  3. Results and Discussion
  4. Crystal structure and structural stability under the unstrained state
  5. Phonon spectra and electron-phonon coupling of the (3,3) carbon nanotube with 4.5% tensile strain
  6. Estimation of superconducting critical temperature
  7. Conclusion
  8. Convergence tests of the EPC constant

Figures (4)

  • Figure 1: (a) and (b), Side view along the $b$ axis and top view along the $c$ axis of the (3,3) carbon nanotube structure. (c) Total energy evolution during molecular dynamics simulation; insets show the side and top views of the final configurations at 300 K after 5 ps. (d) Phonon spectra of the (3,3) carbon nanotube.
  • Figure 2: Comparison of phonon and EPC properties of the (3,3) carbon nanotube in the unstrained state (red) and under 4.5% tensile strain (blue). (a) Phonon dispersion. (b) Corresponding PhDOS. (c) Eliashberg spectral function $\alpha^{2}F(\omega)$ together with the cumulative electron--phonon coupling parameter $\lambda(\omega)$.
  • Figure 3: Evolution of the EPC constant $\lambda$, logarithmic phonon frequency $\omega_{\log}$, and superconducting critical temperature $T_c$ of the (3,3) carbon nanotube as functions of uniaxial tensile strain.
  • Figure 4: Convergence of the EPC constant $\lambda$ as functions of the electronic smearing width $\sigma$ for the (3,3) carbon nanotube under uniaxial tensile strains of 0%, 2%, 4%, 4.5%, 5%, 5.5%, 6%, and 8%. The legend in each panel specifies the axial $\mathbf{k}$-point sampling $1\times 1\times N_k$ used for the Brillouin-zone integrations, while the phonon and EPC calculations employ a fixed $1\times 1\times 4$$\mathbf{q}$-point mesh for all strains.