A Theory That Explains Planar Weight Disparity
26 May 2013
Since the discovery of planar weight disparity (PWD)
as a Tc enhancement mechanism in 2005, more that 110 new superconductors have been
found - 40 of which have Tc's above room temperature.
However, just as a theory to explain high-temperature superconductivity
in the copper-oxides remains elusive, so does an explanation for why
alternating the atomic layers heavy-light improves Tc.
The effect is so strong that every known HTSC copper-oxide can be
shown to exhibit some planar weight disparity along its C axis.
Now, a theory put forth nearly 20 years ago seems to explain why PWD
correlates so strongly with Tc.
In the mid 1990's Howard Blackstead of Notre Dame and John Dow of Arizona State University, postulated that oxygen located in the "chain layer" of a crystal lattice was being compressed into a metallic superconducting state.
"Experimental evidence indicates that the holes of the hypocharged oxygen in
the charge-reservoir regions contribute primarily to the superconductivity,
contrary to most current models of high- temperature superconductivity, which
are based on superconductivity originating in the cuprate-planes. The data
suggest that a successful theory of high-temperature superconductivity will be
BCS-like and will pair holes through the polarization field, perhaps electronic
as well as vibrational polarization."
Blackstead and Dow's argument is compelling when
viewed alongside what has been discovered through the application of planar weight disparity.
Numerous HT superconductors discovered since 2005 have all shown a
sudden drop in quiescent noise below Tc, as shown below. Since background
noise arises from lattice vibrations, a sharp drop in noise when
superconductivity appears is irrefutable evidence that lattice vibrations are
intertwined with the superconductivity mechanism.
Using the simplest structure known to exhibit high-temperature superconductivity,
the infinite layer structure (shown above left), we can see the effect
lattice vibrations have on oxygen layers. Below left, the compound SrCaCu2O4 which has the
highest Tc among the infinite layer superconductors, has been rotated 90 degrees for clarity. (The oxygen atoms are
at the corners of each red square.)
The sinusoidal waveforms near the Sr and Ca atoms show the relative
frequency of each atom's vibration along the C axis. Since strontium is heavier than calcium, it oscillates
at a lower frequency, producing
fewer cycles per unit time. The result is that different vibrational frequencies heterodyne at the oxygen
layer, producing periodic compression proportional to a complex waveform. However with the
Sr2Cu2O4 (non-superconducting) structure to the right, the waveforms
cancel at the oxygen layer, due to identical frequencies producing a null heterodyne.
Ergo, there absolutely
MUST be a difference in mass on opposite sides of the oxygen layer for superconductivity to occur.
No periodic compression = no superconductivity.
When experimentally intermixing various waveform frequencies and
resulting complex waveform increases in amplitude and approaches a more uniform sinusoidal shape as the planar
weight ratio increases. And this is exactly what the plots at page top suggest: greater PWD equates to higher Tc
due to greater and more periodic (BCS-like) compression of the oxygen layers.
1. Howard A. Blackstead and John D. Dow
"Hypercharged copper, hypocharged oxygen, and high-temperature superconductivity", Proc. SPIE 2697,
Oxide Superconductor Physics and Nano-Engineering II, 113 (July 5, 1996); doi:10.1117/12.250277;
E. Joe Eck
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