[Todos] Coloquio (extra) del Departamento de Física (hoy viernes 1/4)

[pdmitruk en df.uba.ar]

Recordamos el coloquio extra de hoy,



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                        COLOQUIOS DEL DEPARTAMENTO DE FÍSICA FCEyN - UBA

                                   http://coloquios.df.uba.ar/


                          En el Aula Federman, 1er piso, Pabellón I,
                                        Ciudad Universitaria

                                 Viernes 1 de abril, 14 hs,

                    Evidence for high-temperature superconductivity at
                         the interfaces of highly oriented graphite

                                       P. Esquinazi

                                   University of Leipzig



The possibility of high-temperature superconductivity at surfaces and
interfaces attracted the attention of the low-temperature community
since the earliest 60 s. Evidence for hightemperature
superconductivity at the interfaces between insulating oxides as well
as between Bi crystalline regions has been published in the last few
years. The existence of intrinsic, nonpercolative high-temperature
superconductivity in highly oriented pyrolytic graphite (HOPG) has
been speculated in the last 10 years. Recently published studies
revealed that the internal structure of HOPG is composed by a stack of
~50 nm thick crystalline graphite regions with interfaces running
parallel to the graphene layers. Magnetoresistance measurements near
an interface between two crystalline graphite regions of a graphite
flake as well as at micro-constrictions showed a behavior compatible
with the existence of non-percolative superconductivity with critical
temperatures above 50K. In my talk I will present a summary of all
these studies and new transport measurements on specially prepared
very thin lamellas of HOPG, which provide evidence for the existence
of two-dimensional Josephson-coupled superconducting regions with
critical temperatures above 100K. The overall results support the view
that HOPG is a system with interfaces containing nonpercolative
superconducting domains immersed in a semiconducting graphene-based
matrix.

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