Superconductivity and magnetism competing in correlated orbitally degenerate light-element molecular solids

Date

Apr 15, 2014

Time

4:40 PM - 6:10 PM

Speaker

Prof. Dr. Denis Arcon

Affiliation

University of Ljubljana

Series

TUD Physikalisches Kolloquium

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Prof. Dr. Carsten Timm, Fachrichtung Physik

Description

Light element molecular solids withs/p-based outer electrons in which a fine balance exists between electron-phonon coupling and electron correlation energies can give rise to some most intriguing electronic properties usually associated only with the transition-metal ions. These systems are naturally narrow-band solids where on-site repulsion is comparable to or larger than the electronic bandwidth. Moreover, in cases when the degeneracy of the frontier molecular orbitals is preserved the interplay between the Hund's rule coupling and Jahn-Teller effect lead to a very rich phase diagram where correlated superconducting state borders the Mott-insulating antiferromagnetic phase [1,2].

In this talk we will first report on our study of face-centred-cubic (f.c.c.) alkali-doped fullerides, A3C60 (A = alkali metal) with triply-degenerated t1u frontier molecular orbitals that can be tuned continuously through the bandwidth-controlled antiferromagnetic Mott insulator-metal/superconductor transition by chemical or physical pressure [1,2]. Both competing phases will be evaluated by employing pressure- and temperature-dependent nuclear magnetic resonance (NMR) studies. In particular, the size and the symmetry of the superconducting gap close to the metal/superconductor-insulator boundary will be examined [3].

Rare-earth sesquicarbide (Ln2C3, Ln = La, Y) or alkali-metal sesquioxide and superoxides (AO2 and A4O6) belong to the same class of molecular solids showing unusual superconductivity [4] and magnetism that depends on the orbital ordering of π∗ molecular orbitals [5]. The richness of these systems stem from the simultaneous presence of orientational, charge, orbital, and spin degrees of freedom that are strongly coupled as revealed from the comprehensive NMR studies.

[1] Y. Takabayashi, D. Arčon et al., Science 323, 1585 (2009).
[2] A. Y. Ganin, D. Arčon et al., Nature 466, 221 (2010).
[3] A. Potočnik et al., Sci. Rep. 4, 4265 (2014).
[4] A. Potočnik, J. Akimitsu and D. Arčon, in preparation.
[5] D. Arčon et al., Phys. Rev. B 88, 224409 (2013).

Links

• http://tu-dresden.de/veranstaltungen/termin?id=TUD5318970a6b1b5

Last modified: Apr 15, 2014, 10:01:50 AM