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The 27th AIRAPT International Conference on High Pressure Science and Technology
Abstract

Oral


Correlation between normal state and superconductivity within the Fermi-liquid regime of the T-p phase diagram of quantum critical heavy Fermion superconductors

Authors:
Pedro B. Castro (IF - UFRJ - Instituto de Fisica, Universidade Federal do Rio de Janeiro) ; Marcello B. Silva Neto (IF - UFRJ - Instituto de Fisica, Universidade Federal do Rio de Janeiro) ; Mohammed Elmassalami (IF - UFRJ - Instituto de Fisica, Universidade Federal do Rio de Janeiro)

Abstract:

As physical pressure is a convenient non-thermal control parameter, the superconducting-normal-state phase diagram of most quantum critical Heavy Fermion (HF) superconductors is usually presented on a temperature versus pressure diagram. By tuning the pressure, one traverses an exotic succession of distinct electronic phases characterized by states that can be magnetic, of Kondo- type, non-conventional superconducting, Fermi Liquid (FL), and non Fermi-liquid, with some of these neighboring states being separated, at T=0 K, by quantum critical points.1-4  Of particular interest is the observation that below a specific phase-boundary, TFL(p), the transport and thermodynamic properties of such HFs switch from non-FL into FL behaviours.1 Then, (i) the resistivity starts to follow a characteristic ro +AT2 law (ro being the residual resistivity and A the FL coefficient); (ii) a superconducting state becomes manifested below Tc<TFL(p), and (iii) each of Tc(p), ro(p) and A(p) decreases monotonically with applied pressure. It is remarkable that, within this FL regime, Tc, ro and A are strongly correlated to each other:5-9 in particular, Tc can be expressed in terms of a BCS-like, ln(Tc/q) µ A-½ relation (q is a characteristic energy scale). Here we show that the origin of these correlations is related to a spin-fluctuation mediated electron-electron interaction channel.10 Assuming such a bosonic, spin-fluctuation exchange mechanism11 and applying the standard Migdal-Eliashberg description of superconductivity as well as Boltzmann's transport theory, we derived analytic expressions that reproduce satisfactorily all experimental correlations. Finally, we discuss also the generalization of our approach to the FL-phase of the Fe-based pnictides and chalcogenide superconductors.

 

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6 V. Taufour, et al.,Phys. Rev. B 89, 220509 (2014).

7 D. van der Marel, et al., Phys. Rev. B 84, 205111(2011).

8 P. B. Castro, et al., J. Phys.: Conf. Ser. 969, 012050 (2018).

9 C. C Soares, et al., Sci. Rep. 8, 7041 (2018).

10 M. ElMassalami and M. B. Silva Neto, (2019), arXiv:1904.04773v1 [cond-mat.supr-con].

11 N. D. Mathur, et al., Nature 394, 39 (1998).