Extraction of the electron-phonon interaction from tunneling data in the multigap superconductor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MgB</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Dolgov, O. V.; Gonnelli, Renato; Ummarino, Giovanni; Golubov, Alexandre Avraamovitch; Shulga, S. V.; Kortus, Jens

doi:10.1103/physrevb.68.132503

Cited by 49 publications

(72 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the following I will refer to the paper of A.F.Goncharov [5] because in there are present both measurement of the variation of critical temperature and of phonon mode by means of Raman measurement, with the pressure and so I mainly refer to these experimental data. In fact only in this work there are all input parameters necessary to my model.Let us start from the generalization of the Eliashberg theory [7,8] for systems with two bands [9], that has already been used with success to study the MgB 2 and related systems [10,11,12,13,14,15]. To obtain the gaps and the critical temperature within the s-wave, two-band Eliashberg model one has to solve four coupled integral equations for the gaps ∆ i (iω n ) and the renormalization functions Z i (iω n ):…”

mentioning

confidence: 99%

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Ummarino¹

2005

Physica C: Superconductivity and its Applications

View full text Add to dashboard Cite

The variation of the superconducting critical temperature Tc as a function of the pressure p in the magnesium diboride M gB2 has been studied in the framework of two-bands Eliashberg theory and traditional phonon coupling mechanism. I have solved the two-bands Eliashberg equations using first-principle calculations or simple assumptions for the variation, with the pressure, of the relevant physical quantities. I have found that the experimental Tc versus p curve can be fitted very well and information can be obtained on the dependence of the electron-phonon interaction matrix < I 2 > by pressure. The pressure dependence of the superconductive gaps ∆σ and ∆π is also predicted.PACS numbers: 74.62.Fj; 74.20.Fg; 74.70.Ad, 74.25.Kc In the last few years, there is an noticeable increase of the study of superconductivity in many elements under pressure [1], such as sulphur (T c = 17 K), oxygen (T c = 0.5 K), carbon in nanotube (T c = 15 K) and diamond forms (T c = 4) K, a non-magnetic state of iron (T c = 1 K), and the light elements lithium (T c = 20 K) and boron (T c = 11 K). The application of external pressure to superconductors can drive the compounds towards or away from lattice instabilities by varying the principal parameters determining the superconducting properties (the electronic density of states at the Fermi energy, the characteristic phonon frequency, and the electron-phonon coupling constant), and it can be used to tune the T c and the superconducting properties. Almost all of the superconducting metallic materials, unlike the previous simple elements, show a decrease of T c with pressure. This negative pressure coefficient was attributed to the volume dependence of the electronic density of states at the Fermi energy and of the effective interaction between the electrons mediated by the electronphonon coupling. Measurements of the influence of pressure on the transition temperature and critical field yield information on the interaction causing the superconductivity. Indeed, the pressure would seem to be a variables whose effects might be capable of immediate theoretical interpretation. The binary alloy M gB 2 , superconductor [2], at ambient pressure, at T = 40 K has, under pressure, a behaviour similar to metallic materials. The magnesium diboride has stimulated intense investigation, both from the theoretical and the experimental point of view. Now the electronic structure of M gB 2 is well understood and the Fermi surface consists of two three-dimensional sheets, from the π bonding and antibonding bands, and two nearly cylindrical sheets from the two-dimensional σ bands [3]. There is a large difference in the electronphonon coupling on different Fermi surface sheets and this fact leads to a multiband description of superconductivity. Theory indicates that the strongest coupling is realized for the near-zone center in-plane optical phonon * Electronic address: E-mail:giovanni.ummarino@infm.polito.it (E 2g symmetry) related to vibration of the B atoms [1]. The superconductivity in M gB 2 has been ...

show abstract

mentioning

confidence: 99%

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Ummarino¹

2005

Physica C: Superconductivity and its Applications

View full text Add to dashboard Cite

show abstract

“…The Eliashberg function of MgB 2 is well documented theoretically as well experimentally, and has been decomposed [19] within multi-band Eliashberg theory on the particular contributions of the participating phonon branches;…”

Section: Model Of Electron-phonon Interactionsmentioning

confidence: 99%

“…We performed numerical conversions of published types of dimensionless Eliashberg functions [19] (Figure 2b). This fact leads us to use a simpler 2-component model with poles at  k = {351.6, 591.9} cm -1 , normalized to the value 1.017.…”

Section: Model Of Electron-phonon Interactionsmentioning

confidence: 99%

“…This material is simple enough for theoretical study, and with its two-gap character it represents the aspects of superconductivity in full complexity. Moreover, the crucial role of EP interactions in transition into a superconducting state is generally accepted and the Eliashberg function  2 F(), which represents the strength of these interactions, is for MgB 2 well established, along with the detailed decomposition on contributions of particular phonon branches [19]. It enables us to treat the dissipative part of excited state dynamics on a quantum mechanical level in a realistic way.…”

Section: Introductionmentioning

confidence: 99%

“…The models of MgB 2 for excited state relaxation dynamics are specified in section 3, along with a specification of EP coupling and of derived forms of electronic and vibration parts of relevant response functions. The results of numerical calculations of relaxation dynamics for our models obtained through the Meier-Tannor decomposition scheme for spectral density [26,27], which is derived from a particular Eliashberg function [19], and from Padé spectral decomposition of a Bose function [28] for calculating the line-shape function across a wide range of temperatures (5-300 K), are presented in section 4. With respect to published experimental OPOP and OPTP results, the theoretical outputs are discussed on the basis of time-dependent diagrammatic perturbation theory in section 5.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory

Baňacký

Szöcs

2016

Physica Status Solidi (b)

View full text Add to dashboard Cite

ReceivedHere we present a quantum-statistical formulation of relaxation dynamics of superconductors related to pump-probe (PP) spectroscopy. The method is based on the perturbation expansion of the non-equilibrium density matrix for calculation of multi-time correlation functions, and the corresponding response function. As a model for our study, the high-temperature superconductor MgB 2 has been selected. Knowledge of the electronic structure and of the corresponding Eliashberg function of electron-phonon (EP) interactions enabled us to distinguish nonequilibrium processes in a sequence of interactions with laser pulses on a microscopic level. Temperature-dependent relaxation dynamics as a function of delay time between the pump and probe pulses have been derived. We have shown that an abrupt increase of the relaxation time at T c is the direct consequence of sudden changes in the character of EP coupling in transition from an adiabatic to a stabilized superconducting anti-adiabatic state, as it predicts the anti-adiabatic theory of electron-vibration interactions. The BCS model, which is based on adiabatic character of EP coupling, is basically unable to reflect the enormous sudden increase of the relaxation time at T c . Differences in the optical pump-optical probe and the optical pump-terahertz probe settings of PP relaxation dynamics are discussed within diagrammatic perturbation theory.Keywords: pump-probe spectroscopy; relaxation dynamics of superconductors; electron-phonon coupling; theory of superconductivity; anti-adiabatic theory of superconductivity IntroductionPump-probe (PP) spectroscopy, a method of nonlinear optics, is an important experimental tool in the study of ultrafast relaxation dynamics of excited states in condensed matter systems [1,2]. The interpretation of experimental results relies on various types of phenomenological equations of motion for the relaxation of "hot electrons" and/or high-energy phonons in coupling to bosonic degrees of freedom [3][4][5][6][7]. The assumption of quasi-equilibrium, which is often behind these methods, is discussed in [8], where the authors present an analytic solution of excited state relaxation dynamics within the Boltzmann kinetic equation, the method of which deals with electrons and phonons out of equilibrium.In general, however, phenomenological treatments not only ignore nonlinear aspects of processes running in PP experiments, but ignore also the microscopic character of nonequilibrium states -coherences and/or populations, which can evolve in the studied system over a sequence of different time periods via the interaction of matter with the incident fields. In these circumstances, mainly in the case of superconductors, it is difficult to disclose the relationship between the derived relaxation parameters, i.e. relaxation times, or electron-phonon (EP) coupling constants (), and the microscopic mechanism of the superconducting state transition. The theory of high-temperature superconductors (e.g. cuprates, pnictides) is far from being settled,...

show abstract

Tunneling density of states of MgB ₂ : evidence for a dominant π‐band contribution

Abal’oshev

Lewandowski

Dyachenko

et al. 2005

phys. stat. sol. (c)

View full text Add to dashboard Cite

, 74.78.Fk Weakly-transmitting junctions usable for tunneling spectroscopy experiments were fabricated from polycrystalline bulk samples of magnesium diboride with a niobium counter-electrode. A strong nonlinear conductance-versus-voltage behavior for voltages above the values corresponding to the energy gaps of the electrodes was interpreted as a fingerprint of the electron-phonon interaction in superconducting MgB2. A partial Eliashberg spectral function α 2 (ω)F (ω) was extracted from the data by the numeric inversion of the standard strong-coupling Eliashberg equations. In a full agreement with recent theoretical simulations for magnesium diboride [1], we have observed a dominant contribution from the π-band of this two-band superconductor.

show abstract

Extraction of the electron-phonon interaction from tunneling data in the multigap superconductorMgB2

Cited by 49 publications

References 23 publications

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory

Tunneling density of states of MgB ₂ : evidence for a dominant π‐band contribution

Contact Info

Product

Resources

About

Extraction of the electron-phonon interaction from tunneling data in the multigap superconductorMgB2

Cited by 49 publications

References 23 publications

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Pressure dependence of critical temperature in MgB2 and two-bands Eliashberg theory

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB2 relaxation within nonlinear response theory

Tunneling density of states of MgB 2 : evidence for a dominant π‐band contribution

Contact Info

Product

Resources

About

Microscopic insight into the pump–probe relaxation dynamics of superconductors: Model study of MgB₂ relaxation within nonlinear response theory

Tunneling density of states of MgB ₂ : evidence for a dominant π‐band contribution