Excitonic Insulator to Superconductor Phase Transition in Ultra-Compressed Helium
arXiv:2301.06756 · doi:10.1038/s41467-023-40240-x
Abstract
Helium, the second most abundant element in the universe, exhibits an extremely large electronic band gap of about eV at low pressures ( GPa). While the metallization pressure of hcp helium has been accurately predicted, thus far little attention has been paid to the specific mechanisms driving the band-gap closure and electronic properties of this quantum crystal in the terapascal regime (1 TPa GPa). Here, we employ state-of-the-art density functional theory and many-body perturbation theory calculations to fill up this knowledge gap. It is found that prior to reaching metallicity bulk solid helium becomes an excitonic insulator (EI), an exotic state of matter typically observed in low-dimensional systems in which electrostatically bound electron-hole pairs form spontaneously. Furthermore, it is shown that electron-phonon coupling (EPC) is significantly enhanced across the EI to metal phase transition as signaled by prominent phonon softening and giant EPC strength values () estimated at specific reciprocal space points. Accordingly, we predict metallic helium to be a superconductor with a critical temperature of K at TPa and of K at TPa. These unforeseen phenomena have important consequences on the elastic, thermodynamic and transport properties of metallic helium hence may be critical for improving our fundamental understanding and modelling of celestial bodies.
arXiv comment25 pages, 18 figures
References in corpus (29)
- Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
- Restoring the density-gradient expansion for exchange in solids and surfaces
- Generalized gradient approximation for solids and their surfaces
- Phonons and related properties of extended systems from density-functional perturbation theory
- Advanced capabilities for materials modelling with Quantum ESPRESSO
- Ab initio Random Structure Searching
- Yambo: an \textit{ab initio} tool for excited state calculations
- High-pressure phases of silane
- High-temperature superfluidity with indirect excitons in van der Waals heterostructures
- An exchange functional that tests the robustness of the plasmon description of the van der Waals density functional
- Anharmonic free energies and phonon dispersions from the stochastic self-consistent harmonic approximation: application to platinum and palladium hydrides
- Quantum Crystal Structure in the 250 K Superconducting Lanthanum Hydride
- Quantum Hydrogen-Bond Symmetrization and High-Temperature Superconductivity in Hydrogen Sulfide
- Strongly correlated excitonic insulator in atomic double layers
- Second order structural phase transitions, free energy curvature, and temperature-dependent anharmonic phonons in the self-consistent harmonic approximation: theory and stochastic implementation
- Evidence for a Monolayer Excitonic Insulator
- Simulation and understanding of quantum crystals
- Lattice dynamics and electron-phonon coupling calculations using non-diagonal supercells
- On the possibility of an excitonic insulator at the semiconductor-semimetal transition
- Current challenges in the physics of white dwarf stars
- Pressure and stress tensor of complex anharmonic crystals within the stochastic self-consistent harmonic approximation
- High-throughput discovery of high-temperature conventional superconductors
- Electron-Phonon Coupling and the Metalization of Solid Helium at Terapascal Pressures
- Electron-Phonon Coupling Mode in Excitonic Insulator
- Excitonic and lattice contributions to the charge density wave in 1T-TiSe revealed by a phonon bottleneck
- Vibrational averages along thermal lines
- Benchmarking Hydrogen-Helium Mixtures with QMC: Energetics, Pressures, and Forces
- Pure-helium 3D model atmospheres of white dwarfs
- First-Principles Modeling of Quantum Nuclear Effects and Atomic Interactions in Solid 4He at High Pressure