[Todos] Coloquios del Departamento de Física (jueves 31/3 y extra viernes 1/4)

[pdmitruk en df.uba.ar]

                         COLOQUIOS DEL DEPARTAMENTO DE FÍSICA FCEyN - UBA

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

                                   Charla, café y galletitas
                         En el Aula Federman, 1er piso, Pabellón I,
                                       Ciudad Universitaria

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                                 Jueves 31 de marzo, 14hs,

                         Semiconductores de silicio, germanio y estaño:
                                   ciencia y aplicaciones

                                      José Menendez

                                Arizona State University


En esta charla se presentan las propiedades físicas y ópticas de  
nuevas familias de semiconductores del Grupo IV que contienen estaño.  
Estos materiales, desarrolados en Arizona State University, poseen  
propiedades únicas, entre las que se encuentran la posibilidad de un  
"gap" directo y el desacople entre el parámetro de red y la estructura  
electrónica. Se discutirán varias aplicaciones de interés incluyendo  
detectores, láseres y celdas sola



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                                 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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