Source zotero
Authors Xin-Wei Yi, Ying Meng, Jia-Wen Li, Zheng-Wei Liao, Wei Li, Jing-Yang You, Bo Gu, Gang Su
arXiv / Publisher https://link.aps.org/doi/10.1103/PhysRevB.110.L140508
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Published 2024-10-18
Research paradigm Unknown
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Summary

Nature of charge density waves and metal-insulator transition in pressurized La3Ni2O7

Materials

Not available in this batch.

Methods

Not available in this batch.

Keywords

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Highlights

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Conclusions

Not available in this batch.

Main claims

  • Superconductivity in pressurized La3Ni2O7 cannot be explained by BCS electron-phonon coupling alone; λ < 0.25 and Tc,BCS ≈ 0.
    • Evidence: Calculated λ from DFT: 0.245 at 0 GPa, decreasing to 0.137 at 50 GPa,McMillan formula gives Tc near zero
  • The magnetic ground state is AFM1 (in-plane double stripe) with interlayer antiferromagnetic coupling; SDW stripe orders are higher in energy.
    • Evidence: Energy of AFM1 is lowest among all tested configurations at both 0 and 29.5 GPa,Stripe orders are tens to hundreds of meV higher
  • Charge density waves (CDW) appear at ambient pressure (CDW-Z1, TCDW ≈ 190 K) and high pressure (CDW-M1, TCDW ≈ 152 K); they compete with superconductivity.
    • Evidence: Imaginary phonon modes at Γ/Z (0 GPa) and M (30 GPa) stabilized into CDW phases,TCDW from phonon energy comparison decreases with pressure and disappears by ≈7.5 GPa,CDW phases have lower TN than pristine

Workflow

  • dft_calculations — CDW phases are identified; AFM1 is ground state.
    • Materials: Crystal structures of La3Ni2O7 (Cmcm, Fmmm, CDW phases)
    • Methods: DFT using VASP and QUANTUM ESPRESSO; PBE-GGA; Projector augmented-wave method; Phonon calculations with phonopy; Eliashberg electron-phonon coupling
    • Observations: Imaginary phonon modes at Γ and Z (0 GPa) and M (30 GPa) indicate CDW instabilities; Four stable CDW phases at low pressure, two at high pressure; AFM1 is magnetic ground state
  • magnetic_monte_carlo_simulations — Neel temperatures calculated; CDW suppresses TN.
    • Materials: 2D and 3D square lattices with exchange parameters from DFT
    • Methods: Monte Carlo simulations; Heisenberg model with J1, J2, J3
    • Observations: TN for pristine-Cmcm: 393 K, CDW-Z1: 190 K, pristine-Fmmm: 304 K, CDW-M1: 152K
  • analysis_of_oxygen_vacancies — Oxygen vacancies affect structural stability and magnetic ordering.
    • Materials: La3Ni2O6.75 models with oxygen vacancies
    • Methods: DFT+U calculations; Enthalpy comparison for half-distortion vs full-distortion phases
    • Observations: Half-distortion phase stable below 2 GPa, full-distortion above; AFM1 remains ground state; Reduced TN in HD phase (95 K)