Small Fermi energy, zero point fluctuations and nonadiabaticity in MgB${}_2$

Abstract

Small Fermi energy effects are induced in MgB${}_2$ by the low hole doping in the $\sigma$ bands which are characterized by a Fermi energy $E_{\mathrm{F}}^{\sigma }\sim 0.5$ eV. We show that, due to the particularly strong deformation potential relative to the $E_{2g}$ phonon mode, lattice fluctuations are reflected in strong fluctuations in the electronic band structure. Quantum fluctuations associated to the zero-point lattice motion are responsible for an uncertainty of the Fermi energy of the order of the Fermi energy itself, leading to the breakdown of the adiabatic principle underlying the Born-Oppenheimer approximation in MgB${}_2$ even if ${\omega }_{\mathrm{ph}}/E_{\mathrm{F}}\sim 0.1-0.2$, where ${\omega }_{\mathrm{ph}}$ are the characteristic phonon frequencies. This amounts to a new nonadiabatic regime, which could be relevant to other unconventional superconductors.

arXiv commentto appear on Physical Review B

References in corpus (10)

• Superconductivity of metallic boron in MgB_2
• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Superconductivity of MgB2: Covalent Bonds Driven Metallic
• Electron-phonon interaction in the normal and superconducting states of MgB2
• Giant anharmonicity and non-linear electron-phonon coupling in MgB${}_2$; A combined first-principles calculations and neutron scattering study
• Electronic structure of MgB${}_2$ from angle-resolved photoemission spectroscopy
• Small Fermi energy and phonon anharmonicity in MgB_2 and related compounds
• High $T_c$ superconductivity in MgB${}_2$ by nonadiabatic pairing
• muSR study of carbon-doped MgB2 superconductors
• Band-filling effects on electron-phonon properties of normal and superconducting state

Cited by in corpus (16)

• A Perspective on Conventional High-Temperature Superconductors at High Pressure: Methods and Materials
• Breakdown of the Migdal approximation at Lifshitz transitions with giant zero-point motion in H3S superconductor
• Superconductivity above the lowest Earth temperature in pressurized sulfur hydride
• Electron-phonon effects on the Raman spectrum in MgB${}_2$
• Ultrafast Hot Phonon Dynamics in MgB${}_2$ Driven by Anisotropic Electron-Phonon Coupling
• Study of temperature dependent atomic correlations in MgB${}_2$
• Anharmonicity and self-energy effects of the E2g phonon in MgB2
• Lifshitz transitions and zero point lattice fluctuations in sulfur hydride showing near room temperature superconductivity
• Multi-Gap Superconductivity in MgB2: Magneto-Raman Spectroscopy
• Zero point motion and direct/indirect bandgap crossover in layered transition-metal dichalcogenides
• Aspects of strong electron-phonon coupling in superconductivity of compressed metal hydrides MH6 with Im-3m structure
• Electronic structure of single-wall silicon nanotubes and silicon nanorribons: Helical symmetry treatment and effect of dimensionality
• Toward possibility of high-temperature bipolaronic superconductivity in boron tubular polymorph: Theoretical aspects of transition into anti-adiabatic state
• Large diameter multiwall nanotubes of MgB2: structural aspects and stability of superconducting nanotubular magnesium boride
• Microscopic insight on the pump-probe relaxation dynamics of superconductors: Model study of MgB2 relaxation within nonlinear response theory
• Properties and challenges of hot-phonon physics in metals: MgB${}_2$ and other compounds