[Paper Review] A comprehensive first principles calculations on (Ba0.82K0.18)(Bi0.53Pb0.47)O3 single-cubic-perovskite superconductor

Mirza H. K. Rubel, S.K. Mitro+8 more|arXiv (Cornell University)|Dec 7, 2021

Physics of Superconductivity and Magnetism6 citations

TL;DR

This study employs first-principles density functional theory (DFT) calculations to investigate the electronic, elastic, and superconducting properties of the (Ba0.82K0.18)(Bi0.53Pb0.47)O3 (BKBPO) perovskite superconductor. It reveals a high electron-phonon coupling constant (λ = 1.46), strong orbital hybridization centered at the Fermi level, multi-band Fermi surfaces, and significant anisotropy, indicating BKBPO as a strongly coupled, multi-band superconductor with potential for high-Tc behavior.

ABSTRACT

In this present study, the pseudopotential plane-wave (PP-PW) pathway in the scheme of density functional theory (DFT) is utilized to investigate the various physical properties on (Ba0.82K0.18)(Bi0.53Pb0.47)O3 (BKBPO) single perovskite superconductor. We have analyzed elastic constants and moduli at zero and elevated pressures (up to 25 GPa) as well. We also have investigated the anisotropic nature incorporating both the theoretical indices and graphical representations in 2D and 3D dimensions, which reveals a high level of anisotropy. The flatness of the energy bands near EF is a sign of Van-Hf singularity that might increase the electron pairing and origination of high-TC superconductivity. The computed band structure exhibits its metallic characteristics is confirmed by band overlapping. A band of DOS is formed for the strong hybridization of the constituent elements. The orbital electrons of O-2p contribute most dominantly at EF in contrast to all orbital electrons. The orbital electrons at the EF are higher from both the partial density of states and charge density mapping investigation. The coexistence of the electron and hole-like Fermi sheets exhibits the multi-band nature of BKBPO. On the other hand, Fermi surfaces with flat faces promote transport features and Fermi surface nesting as well. The calculated value of the electron-phonon coupling constant (λ = 1.46) is slightly lower than the isostructural superconductor, which indicates that the studied BKBPO can be treated as a strongly coupled superconductor similar to the reported isostructural perovskite superconductors. Furthermore, the thermodynamic properties have been evaluated and analyzed at elevated temperature and pressure by using harmonic Debye approximation (QHDA).

Motivation & Objective

• To investigate the electronic and superconducting properties of the (Ba0.82K0.18)(Bi0.53Pb0.47)O3 (BKBPO) single-cubic perovskite superconductor using first-principles methods.
• To analyze the elastic behavior and mechanical stability of BKBPO under zero and elevated pressures (up to 25 GPa).
• To explore the anisotropic nature of BKBPO using theoretical indices and 2D/3D graphical representations.
• To determine the origin of high-Tc superconductivity by examining electronic structure, Fermi surface topology, and orbital contributions near the Fermi level.
• To evaluate thermodynamic properties at elevated temperature and pressure using the harmonic Debye approximation (QHDA).

Proposed method

• Employed the pseudopotential plane-wave (PP-PW) method within the framework of density functional theory (DFT) for electronic structure calculations.
• Calculated elastic constants and moduli at zero and up to 25 GPa to assess mechanical stability and anisotropy.
• Used Fermi surface topology and band structure analysis to investigate multi-band character and nesting features.
• Performed partial density of states (PDOS) and charge density mapping to identify dominant orbital contributions at the Fermi level.
• Computed the electron-phonon coupling constant (λ) to assess superconducting pairing strength.
• Applied the harmonic Debye approximation (QHDA) to evaluate thermodynamic properties under elevated temperature and pressure.

Experimental results

Research questions

• RQ1 What is the electronic structure and Fermi surface topology of BKBPO, and how do they support multi-band superconductivity?
• RQ2 How does the electron-phonon coupling constant (λ) in BKBPO compare to isostructural perovskite superconductors, and what does this imply for superconducting pairing?
• RQ3 To what extent is BKBPO anisotropic in its mechanical and electronic properties, and how does this affect its superconducting behavior?
• RQ4 Which atomic orbitals contribute most significantly to the electronic states at the Fermi level in BKBPO?
• RQ5 How do thermodynamic properties of BKBPO evolve under elevated temperature and pressure?

Key findings

• The electron-phonon coupling constant λ = 1.46 indicates that BKBPO is a strongly coupled superconductor, similar to other isostructural perovskite superconductors.
• The band structure exhibits metallic character due to band overlapping, and a flat band near the Fermi level suggests a Van Hove singularity that may enhance electron pairing.
• O-2p orbitals dominate the electronic states at the Fermi level, with significant hybridization among constituent elements forming a distinct band in the density of states.
• The coexistence of electron- and hole-like Fermi sheets confirms the multi-band nature of BKBPO, with flat Fermi surface faces promoting nesting and transport properties.
• The material exhibits strong anisotropy in both elastic and electronic responses, as revealed by theoretical indices and 2D/3D graphical representations.
• Thermodynamic properties were successfully evaluated at elevated temperature and pressure using the harmonic Debye approximation, supporting stability under extreme conditions.