[Paper Review] First-principles prediction of high-temperature superconductivity in stretched carbon nanotubes

Hua-Zhen Li, Xun-Wang Yan|arXiv (Cornell University)|Mar 16, 2026

Carbon Nanotubes in Composites0 citations

TL;DR

The paper uses first-principles calculations to show that uniaxial tensile strain can dramatically enhance electron-phonon coupling in (3,3) carbon nanotubes, predicting a Tc up to around 162–287 K depending on the formalism, with 4.5% strain as optimal.

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.

Motivation & Objective

• Investigate superconductivity in a quasi-one-dimensional carbon nanotube under uniaxial tensile strain using first-principles methods.
• Assess how strain-induced phonon softening and changes in electronic DOS at the Fermi level influence electron-phonon coupling (EPC).
• Predict superconducting critical temperatures via McMillan and Allen–Dynes formalisms under varying strain.

Proposed method

• Density functional theory calculations with PBE exchange-correlation and PAW potentials.
• VASP for electronic structure and structural relaxation; Quantum Espresso for DFPT phonons and EPC.
• Calculation of Eliashberg function α^2F(ω), EPC constant λ, ω_log, and ⟨ω^2⟩, using standard Allen–Dynes/McMillan formulations.
• Application of uniaxial tensile strain (0–8%) to the (3,3) carbon nanotube and convergence tests for k-point sampling and smearing parameter σ.
• Assessment of dynamic stability via phonon dispersion and molecular dynamics at 300 K.

Experimental results

Research questions

• RQ1 Can uniaxial tensile strain enhance electron-phonon coupling in a quasi-1D carbon nanotube?
• RQ2 What is the strain dependence of λ, ω_log, and N(EF) for the (3,3) nanotube?
• RQ3 What strain yields the maximum predicted Tc, and how do McMillan and Allen–Dynes Tc estimates compare?
• RQ4 Is the strained structure dynamically stable and free of imaginary phonon modes?

Key findings

• Strain causes overall softening of phonons and a redistribution of phonon states toward low frequencies, particularly under 4.5% strain.
• EPC strength dramatically increases with strain, with λ rising from 0.49 (0% strain) to 16.73 at 4.5% strain.
• Electronic DOS at the Fermi level increases with strain, reaching N(EF) = 6.23 at 4.5% strain.
• Tc estimates peak at ~162–287 K around 4.5% strain depending on the Tc model (McMillan ≈ 83.6 K; Allen–Dynes ≈ 287.1 K).
• Beyond 4.5% strain, λ decreases and Tc drops (e.g., at 6% and 8% strain, Tc from Allen–Dynes is ~51–62 K).
• The 4.5% tensile strain is identified as optimal for potential high-Tc superconductivity in the (3,3) nanotube.