Mercoledì 18 Marzo 2015 - Ore 16:30 - Seminario di Dipartimento - Stephen Blundell - Iron superconductors: high transition temperatures in molecular intercalates of FeSe

Relatore: Stephen Blundell - Department of Physics, Oxford University

Luogo: Aula Newton - Plesso Fisico

E-mail organizzatore: raffaella.burioni@fis.unipr.it

Stephen Blundell  is Professor of Physics at Oxford University, Fellow of

Manfield College and past Head of Condensed Matter at Clarendon.

He is coauthor of over three hundred papers and several best seller books,

including undergraduate textbooks Concepts in Thermal Physics, Magnetism

in Condensed Matter,  Quantum Field Theory for the Gifted Amateur, plus two

easy-to-read booklets for a more general audience:  A Very Short

Introduction to Magnetism, and A Very Short Introduction to

Superconductivity, all by Oxford University Press. Quoting from the

Contemporary Physics review of the VSI to Magnetism, This quite amazing

book covers practically everything there is to know about magnetism, …,

written in a relaxed, engaging, easy-to-follow style, which the author

maintains throughout.

Prof. Blundell's research is concerned with using muon-spin rotation and

magnetoresistance techniques to study a range of organic and inorganic

materials, particularly those showing interesting magnetic,

superconducting, or dynamical properties. He is a very brilliant lecturer

who knows how to combine rigour, wit and accessibility to a vast audience.

Abstract:

Molecular groups can now be intercalated into iron-based superconductors with dramatic

consequences on the superconducting properties. These species act as charge reservoirs, sources of electrical

polarization, and also make subtle structural modifications to superconducting layers, all of which can make

novel adjustments to the band structure that in turn can control superconducting properties. By synthesizing

the compound Lix(NH2)y(NH3)1−yFe2Se2 (x ~ 0.6; y ~ 0.2), in which lithium ions, lithium amide and

ammonia (NH3) act as the spacer layer between FeSe layers, we have turned a 9 K superconductor into a 43

K superconductor. Further chemical modification allow us to produce a range of new superconducting

materials which we have studied using a variety of techniques including muon-spin rotation. Recently, we

have used hydrothermal reactions to produce layered lithium iron selenide hydroxides with chemical formula

Li1–xFex(OH)Fe1–ySe and thereby producing compounds whose transition temperature can be tuned from

zero up to about 40 K. Minimizing the concentration of iron vacancies in the iron selenide layer and

simultaneously increasing the electron count on iron in the selenide layers enhance the superconducting

properties in this family. Future prospects for new superconducting materials using these novel synthetic

routes will be discussed, as will also our current understanding of the superconductivity in these materials.