Monday, November 18, 2013

Physics Colloquium - Fri., Nov. 22, 2013, 4:30, PSB 161

The Wonderful World of BSCCO

Richard Klemm, UCF
The high-temperature superconductor with rough stoichiometry Bi2Sr2CaCu2O8+d (BSSCO or Bi2212) is one of the most anisotropic materials known. In the normal state above the superconducting transition temperature Tc ~ 90 K, it behaves as a metal parallel to the layers, and an insulator normal to them.  Although nominally orthorhombic in structure, microscopic analyses have confirmed that the insulating Bi2O2 double layers have a lateral periodicity that is incommensurate with that of the conducting CuO2 double layers, so that it is really a ``misfit’’ compound.  The c-axis transport for electrons in the normal state and quasiparticles in the superconducting state is 100% incoherent. The primary interest in BSCCO, is that although its lateral structure is extremely irregular, its intrinsic Josephson junction structure is so perfect, that application of a dc voltage V across a stack of N junctions leads to coherent sub-THz emission due to the ac Josephson effect at the frequency f=f_J=(2eV)/(Nh), where e is the electronic charge and h is Planck’s constant.  Although plagued with heating effects, the design of BSCCO mesas has developed to the point where output powers of 1 mW should be attainable in the near future, allowing continuous wave, coherent, high-power devices to be manufactured that can fill the ``THz gap’’ range of 0.3-1.5 THz with a hand-held device.

Contact:  Pat Korosec     3-2325

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