Density Functional Theory for Plasmon-Assisted Superconductivity

Two hydrogen-rich materials: H 3 S and LaH 10 , synthesized at megabar pressures have revolutionized the field of superconductivity by providing a first glimpse into the solution for the hundred-year-old problem of room-temperature superconductivity. The mechanism governing these exceptional superconductors is the conventional electron-phonon coupling. Here, we describe recent advances in experimental techniques, superconductivity theory and first-principles computational methods, which made this discovery possible. The aim of this work is to provide an up-to-date compendium of the available results on superconducting hydrides and explain the synergy of different methodologies that led to the extraordinary discoveries in the field. Furthermore, in an attempt to evidence empirical rules governing superconductivity in binary hydrides under pressure, we discuss general trends in electronic structure and chemical bonding. The last part of the Review introduces possible strategies to optimize pressure and transition temperatures in conventional superconducting materials. Directions for future research in areas of theory, computational methods and high-pressure experiments are proposed, in order to advance our understanding of superconductivity.

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“…Several approximations for F xc have been proposed and tested [34, 263,264,235,265], and all lead to a BCS-like form of the equation above:…”

Section: Band Decoupling Approximationmentioning

confidence: 99%

A perspective on conventional high-temperature superconductors at high pressure: Methods and materials

et al. 2020

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“…(23) is also useful to exclude the contribution to the electron-density modulation from the possible change in the Fermi energy in the case of q = 0 [the additional contribution given in Eqs. (11) and (12)]. The possible change in the Fermi energy originates from the intraband transitions at the Fermi level, which are the transition processes in the t-subspace and hence are excluded by employingβ n,m .…”

Section: A Basic Idea and Practical Implementationmentioning

confidence: 99%

Ab initiodownfolding for electron-phonon-coupled systems: Constrained density-functional perturbation theory

Nomura

Arita

2015

Phys. Rev. B

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We formulate an ab initio downfolding scheme for electron-phonon coupled systems. In this scheme, we calculate partially renormalized phonon frequencies and electron-phonon coupling, which include the screening effects of high-energy electrons, to construct a realistic Hamiltonian consisting of low-energy electron and phonon degrees of freedom. We show that our scheme, which we call constrained density-functional perturbation theory (cDFPT), can be implemented by slightly modifying the conventional DFPT, which is one of the standard methods to calculate phonon properties from first principles. Our scheme can be applied to various phonon-related problems, such as superconductivity, electron and thermal transport, thermoelectricity, piezoelectricity, dielectricity and multiferroicity. We believe that the cDFPT provides a firm basis for the understanding of the role of phonons in strongly correlated materials. Here, we apply the scheme to the fullerene superconductors and discuss how the realistic low-energy Hamiltonian is constructed.

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“…Instead, if we had the equivalent of a BCS or Eliashberg theory at our disposal with a corresponding prediction of T c from the microscopic parameters, we could have arrived at a different conclusion. For example, it has been suggested, 131 for an s-wave superconductor, that a large on-site repulsion U can also increase T c in the frequency region where the gap function becomes negative since, then, the product between U and the gap leads to an effective attractive interaction. Nevertheless, even if one could expect the same thing to happen with V , here we found that at infinite frequency, V is definitely pair-breaking.…”

Section: Pairing Mechanism Retardation and Gluementioning

confidence: 99%

Antagonistic effects of nearest-neighbor repulsion on the superconducting pairing dynamics in the doped Mott insulator regime

et al. 2016

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The nearest-neighbor superexchange-mediated mechanism for d x 2 −y 2 superconductivity in the one-band Hubbard model faces the challenge that nearest-neighbor Coulomb repulsion can be larger than superexchange. To answer this question, we use cellular dynamical mean-field theory (CDMFT) with a continuous-time quantum Monte Carlo solver to determine the superconducting phase diagram as a function of temperature and doping for on-site repulsion U = 9t and nearest-neighbor repulsion V = 0, 2t, 4t. In the underdoped regime, V increases the CDMFT superconducting transition temperature T d c even though it decreases the superconducting order parameter at low temperature for all dopings. However, in the overdoped regime V decreases T d c . We gain insight into these paradoxical results through a detailed study of the frequency dependence of the anomalous spectral function, extracted at finite temperature via the MaxEntAux method for analytic continuation. A systematic study of dynamical positive and negative contributions to pairing reveals that even though V has a high-frequency depairing contribution, it also has a low frequency pairing contribution since it can reinforce superexchange through J = 4t 2 /(U − V ). Retardation is thus crucial to understand pairing in doped Mott insulators, as suggested by previous zero-temperature studies. We also comment on the tendency to charge order for large V and on the persistence of d-wave superconductivity over extended-s or s + d-wave.

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Density Functional Theory for Plasmon-Assisted Superconductivity

Cited by 39 publications

References 83 publications

A perspective on conventional high-temperature superconductors at high pressure: Methods and materials

A perspective on conventional high-temperature superconductors at high pressure: Methods and materials

Ab initiodownfolding for electron-phonon-coupled systems: Constrained density-functional perturbation theory

Antagonistic effects of nearest-neighbor repulsion on the superconducting pairing dynamics in the doped Mott insulator regime

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