Department of Physics

Department News

Graduate Seminar Announcement for April 21

Apr 16, 2014

*****Seminar Announcement*****
PHYS 600, Monday, April 21, 4:00 pm
Currens Hall 205
All physics faculty and students are invited.

Speaker: Awwad Nasser Alotaibi
Graduate Student, Physics Department, WIU
Title: Doping Evolution of Absolute Value of the London Penetration Depth and Superfluid Density in Single Crystals of Ba(Fe1xCox)2As2


In this study, single crystals of Ba(Fe1-xCox)2As2 were coated with Al to measure the zero-temperature value of the in-plane London penetration depth as a function of Co concentration "x" in the area of the phase diagram for the superconductivity of the under-doping and over-doping regions by using the TDR technique. Values for »ab(0) were found to sharply increase from between 120±50 and 300±50 nm for xe0.047 to 950±50 nm for xd0.047. This increase corresponds to the region of the coexistence and competition between the itinerant antiferromagnetic and superconducting phases. From these values of »ab(0), the superfluid density was constructed and studied as a function of Co concentration. Its behavior is consistent with multiple superconducting gaps in these superconductors.

Speaker: Saleh Almansour
Graduate Student, Physics Department, WIU
Title: Types of Diodes


A diode is a two terminal electrical component with low resistance to current in one direction and high resistance to current in the opposite direction. Diodes are classified as thermal (vacuum) diodes or semiconductor (solid state) diodes. A thermal diode has two electrodes enclosed in an evacuated glass envelope, one of which is a heated cathode. A semiconductor diode is made of semiconducting material with a p-n junction connected to two terminals. The rectifying ability of some crystals was first observed in 1874 and the first semiconductor diodes were developed in 1906. Thermionic diodes were developed separately around the same time. The presentation focuses on the basic function of diodes, different types of diodes, and their applications with emphasis on the negative differential region of the tunnel diode.

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