Near-degeneracy of extended s+dx2-y2 and dxy order parameters in quasi-two-dimensional organic superconductors

Daniel Guterding, Michaela Altmeyer, Harald Olaf Jeschke, Roser Valentí

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The symmetry of the superconducting order parameter in quasi-two-dimensional bis-ethylenedithio-tetrathiafulvalene (BEDT-TTF) organic superconductors is a subject of ongoing debate. We report ab initio density-functional-theory calculations for a number of organic superconductors containing κ-type layers. Using projective Wannier functions, we derive the parameters of a common low-energy Hamiltonian based on individual BEDT-TTF molecular orbitals. In a random-phase approximation spin-fluctuation approach, we investigate the evolution of the superconducting pairing symmetry within this model, and we point out a phase transition between extended s+dx2-y2 and dxy symmetry. We discuss the origin of the mixed order parameter and the relation between the realistic molecule description and the widely used dimer approximation. Based on our ab initio calculations, we position the investigated materials in the obtained molecule model phase diagram, and we simulate scanning tunneling spectroscopy experiments for selected cases. Our calculations show that many κ-type materials lie close to the phase-transition line between the two pairing symmetry types found in our calculation, possibly explaining the multitude of contradictory experiments in this field.

Original languageEnglish
Article number024515
JournalPhysical Review B
Volume94
Issue number2
DOIs
Publication statusPublished - Jul 19 2016
Externally publishedYes

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organic superconductors
Superconducting materials
symmetry
Phase transitions
Hamiltonians
Spin fluctuations
Molecules
Molecular orbitals
approximation
Dimers
Phase diagrams
Density functional theory
molecules
molecular orbitals
Experiments
dimers
phase diagrams
Spectroscopy
density functional theory
Scanning

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Near-degeneracy of extended s+dx2-y2 and dxy order parameters in quasi-two-dimensional organic superconductors. / Guterding, Daniel; Altmeyer, Michaela; Jeschke, Harald Olaf; Valentí, Roser.

In: Physical Review B, Vol. 94, No. 2, 024515, 19.07.2016.

Research output: Contribution to journalArticle

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