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
No comments:
Post a Comment