By using variational wave functions and quantum Monte Carlo techniques, we investigate the interplay between electron-electron and electron-phonon interactions in the two-dimensional Hubbard-Holstein model. Here, the ground-state phase diagram is triggered by several energy scales, i.e., the electron hopping t, the on-site electron-electron interaction U, the phonon energy omega(0), and the electron-phonon coupling g. At half filling, the ground state is an antiferromagnetic insulator for U >= 2g(2)/omega(0), while it is a charge-density-wave (or bipolaronic) insulator for U <= 2g(2) omega(0). In addition to these phases, we find a superconducting phase that intrudes between them. For omega(0)/t = 1, superconductivity emerges when both U/t and 2g(2)/t omega(0) are small; then, by increasing the value of the phonon energy omega(0), it extends along the transition line between antiferromagnetic and charge-density-wave insulators. Away from half filling, phase separation occurs when doping the charge-density-wave insulator, while a uniform (superconducting) ground state is found when doping the superconducting phase. In the analysis of finite-size effects, it is extremely important to average over twisted boundary conditions, especially in the weak-coupling limit and in the doped case.

Superconductivity, charge-density waves, antiferromagnetism, and phase separation in the Hubbard-Holstein model / Karakuzu, Seher; Tocchio, Luca F.; Sorella, Sandro; Becca, Federico. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 96:20(2017), pp. 1-10. [10.1103/PhysRevB.96.205145]

Superconductivity, charge-density waves, antiferromagnetism, and phase separation in the Hubbard-Holstein model

Karakuzu, Seher
Data Curation
;
Tocchio, Luca F.
Writing – Review & Editing
;
Sorella, Sandro
Supervision
;
Becca, Federico
Supervision
2017-01-01

Abstract

By using variational wave functions and quantum Monte Carlo techniques, we investigate the interplay between electron-electron and electron-phonon interactions in the two-dimensional Hubbard-Holstein model. Here, the ground-state phase diagram is triggered by several energy scales, i.e., the electron hopping t, the on-site electron-electron interaction U, the phonon energy omega(0), and the electron-phonon coupling g. At half filling, the ground state is an antiferromagnetic insulator for U >= 2g(2)/omega(0), while it is a charge-density-wave (or bipolaronic) insulator for U <= 2g(2) omega(0). In addition to these phases, we find a superconducting phase that intrudes between them. For omega(0)/t = 1, superconductivity emerges when both U/t and 2g(2)/t omega(0) are small; then, by increasing the value of the phonon energy omega(0), it extends along the transition line between antiferromagnetic and charge-density-wave insulators. Away from half filling, phase separation occurs when doping the charge-density-wave insulator, while a uniform (superconducting) ground state is found when doping the superconducting phase. In the analysis of finite-size effects, it is extremely important to average over twisted boundary conditions, especially in the weak-coupling limit and in the doped case.
2017
96
20
1
10
205145
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.96.205145
https://arxiv.org/abs/1709.00278
Karakuzu, Seher; Tocchio, Luca F.; Sorella, Sandro; Becca, Federico
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/68313
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