Role of anharmonicity in the high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>superconductors

Zacher, Robert A.

doi:10.1103/physrevb.36.7115

Cited by 14 publications

(4 citation statements)

References 6 publications

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“…The discrepancy, that of x-ray data pointing towards a harmonic solid whereas Mossbauer data pointing towards an anharmonic solid has been attributed to the sensitivity of the Mossbauer technique to anharmonic contributions due to higher order terms [10]. It has been argued that anharmonicity is an essential feature of both intermetallic [18,19,24] and metal oxide supercondutors [20][21][22][23].…”

Section: Introductionmentioning

confidence: 98%

On mossbauer dynamics in Nb3Sn

Razdan

2000

Pramana - J Phys

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Section: Introductionmentioning

confidence: 98%

On mossbauer dynamics in Nb3Sn

Razdan

2000

Pramana - J Phys

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“…In the context of high T c superconductors, the effect of anharmonic enhancement on T c has been studied in the early days following the discovery of high-T c superconductivity in the cuprates. In particular, several works by Plakida and others have studied the effect of anharmonicity on T c for the case of structurally unstable lattices or deformed lattice potentials [6][7][8]. Even more recent works on the high-T c hydrides [9][10][11][12][13][14][15][16][17][18][19] only take into consideration phonon energy renormalizations due to anharmonicity but neglect anharmonic damping.…”

Section: Introductionmentioning

confidence: 99%

Anharmonic phonon damping enhances theTcof BCS-type superconductors

2020

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A theory of superconductivity is presented where the effect of anharmonicity, as entailed in the acoustic, or optical, phonon damping, is explicitly considered in the pairing mechanism. The gap equation is solved including diffusive Akhiezer damping for longitudinal acoustic phonons or Klemens damping for optical phonons, with a damping coefficient which, in either case, can be directly related to the Grüneisen parameter and hence to the anharmonic coefficients in the interatomic potential. The results show that the increase of anharmonicity has a strikingly non-monotonic effect on the critical temperature Tc. The optimal damping coefficient yielding maximum Tc is set by the velocity of the bosonic mediator. This theory may open up unprecedented opportunities for material design where Tc may be tuned via the anharmonicity of the interatomic potential, and presents implications for the superconductivity in the recently discovered hydrides, where anharmonicity is very strong and for which the anharmonic damping is especially relevant.

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“…Moreover, there are systems where a strong electron-phonon coupling is measured. For example, high-temperature superconductors are systems where both strong electron-phonon coupling and anharmonicity often coexist [6][7][8][9] . Indeed, the impact of anharmonicity/multi-phonon processes on superconductivity has been often analyzed in the literature, not only by including higher-order terms from perturbation theory in the calculation of the EPI 10 , but also proposing generalizations of the standard electron-phonon formula to compute it, where matrix elements between anharmonic excited states of the nuclei are considered at linear level w.r.t.…”

Section: Introductionmentioning

confidence: 99%

Non-perturbative theory of the electron-phonon coupling and its first-principles implementation

Bianco¹,

Errea²

2023

Preprint

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The harmonic approximation of ionic fluctuations and the linear coupling between phonons and electrons provide the basic approach to compute, from first principles, the contribution that the nuclei dynamics and its interaction with electrons have on materials' properties. These approaches are questionable, at least, whenever quantum and anharmonic effects on the nuclei vibrational properties are large, such as in hydrogenous systems, high-Tc superconductors, and when systems are close to charge-density wave or ferroelectric displacive phase transitions. Here we propose a novel non-perturbative approach to compute the electron-phonon interaction from first principles that includes non-linear effects and takes into account the quantum nature of nuclei. The method is based on the GW (en) approximation for the electron self-energy, given by the effective nucleimediated electron-electron interaction W (en) and the electron Green's function G. The electrons are treated at a mean-field level and the nuclei dynamics is described with a Gaussian distribution function, which can effectively take into account anharmonic effects at a mean-field level, e.g. within the self-consistent harmonic approximation. The pivotal quantities of the Gaussian GW (en) self-energy are the Debye-Waller-renormalized average vertices, which are computed in supercells with a stochastic approach, using the the self-consistent electronic potential computed for different atomic configurations. In order to validate the method, GW (en) calculations are performed on aluminum, a highly harmonic system with weak electron-phonon coupling. As expected, the obtained results coincide with the ones obtained with standard linear electron-phonon calculations. However, calculations performed on palladium hydride, a very anharmonic system, show a highly non-linear electron-phonon interaction, with GW (en) bringing corrections as high as the linear-order result. The performed analysis shows that the developed method may have a large impact on the ab initio calculations of all the properties related to the electron-phonon interaction, e.g. superconductivity and electrical conductivity, in highly anharmonic systems.

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Role of anharmonicity in the high-Tcsuperconductors

Cited by 14 publications

References 6 publications

On mossbauer dynamics in Nb3Sn

On mossbauer dynamics in Nb3Sn

Anharmonic phonon damping enhances theTcof BCS-type superconductors

Non-perturbative theory of the electron-phonon coupling and its first-principles implementation

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