A hybrid Monte Carlo study of bond-stretching electron-phonon interactions and charge order in the bismuthate family of superconductors

Abstract

The role of electron-phonon (e-ph) interactions and their relationship to charge-density-wave (CDW) order in the bismuthate family of high-temperature superconductors remains unresolved. We address this question using state-of-the-art nonperturbative hybrid quantum Monte Carlo calculations for the parent compound BaBiO3. Our model includes the Bi 6s and O 2pσ orbitals and coupling to the Bi-O bond-stretching branch of optical phonons via the modulation of the Bi-O hopping integral. Using recently proposed algorithms that are fast and scalable, we perform simulations on large three-dimensional clusters of up to 4000 orbitals, with input model parameters taken directly from ab initio electronic structure calculations and a physically motivated phonon energy Ω0 = 60 meV. Our results demonstrate that the coupling to the bond-stretching modes is sufficient to account for the CDW transition in this system, despite the relatively small dimensionless coupling to this branch predicted by density functional theory. We also find that the transition deviates from the weak-coupling Peierls picture, despite the noninteracting Fermi surface being well-nested at the CDW ordering vector. Our results highlight the richness of e-ph interactions that are off-diagonal in orbital space and suggest that such interactions play a crucial role in establishing the bismuthate phase diagram.

Flexible class of exact Hubbard-Stratonovich transformations

“…As another example, the fictitious momentum in HMC yields inertial dynamics that can reduce the dynamical critical exponent z [15]. Such sampling methods were originally developed in the context of lattice gauge theory, and have more recently proved to be highly effective for simulation of electronphonon models [16][17][18][19].…”

Ground state and spectral properties of the doped one-dimensional optical Hubbard-Su-Schrieffer-Heeger model

“…This microscopic coupling mechanism thus modulates the electron's kinetic energy as opposed to its potential energy as in the canonical Holstein [2] or Fröhlich [3] models. While the SSH model in one-dimension (1D) has been studied extensively since its inception, interest in SSH-like interactions 1 in a broader class of models and systems has recently surged [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. This activity has been driven by the realization that such interactions can lead to several novel effects, including the stabilization of nontrivial topological states [19,20,23,24] and Dirac points [8], novel bipolaronic charge-density wave [10,16,21] and bond-wave [15,22] orderings, and the formation of mobile bipolarons [9].…”

“…While the SSH model in one-dimension (1D) has been studied extensively since its inception, interest in SSH-like interactions 1 in a broader class of models and systems has recently surged [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. This activity has been driven by the realization that such interactions can lead to several novel effects, including the stabilization of nontrivial topological states [19,20,23,24] and Dirac points [8], novel bipolaronic charge-density wave [10,16,21] and bond-wave [15,22] orderings, and the formation of mobile bipolarons [9]. There is also a recent proposal that a dilute gas of SSH-bipolarons can have an instability towards a high-temperature (high-T c ) superconducting state [14].…”

“…not limited to) quasi-1D [25,26] and 2D cuprates [5,[27][28][29][30][31][32][33][34][35], manganites [36,37], the rare-earth nickelates [38,39], and other oxides [16,[40][41][42][43][44]. In many of these examples, the relevant modes involve the bond-stretching motion of the transition metal and oxygen atoms, which is naturally described by the SSH coupling mechanism.…”