Historical research guide · 0611 · 2007
Tests of new physics from precise measurements of the Casimir pressure between two gold-coated plates
R. S. Decca · D. López · E. Fischbach · G. L. Klimchitskaya · D. E. Krause · V. M. Mostepanenko
In one minute
Two conducting surfaces held a few hundred nanometres apart in vacuum pull toward each other, because the boundaries reshape the zero-point field in the gap. Ricardo Decca and five colleagues measured that pull more precisely than anyone had before, using a micromechanical torsion oscillator: a gold-coated plate hanging on serpentine springs with a gold-coated sphere above it, whose resonant frequency shifts by an amount that converts straight into Casimir pressure. Averaging thirty-three runs taken at the same 293 separations, they pushed the total error down to 0.19 percent at 160 nanometres, and for the first time in this field the random scatter fell below the systematic error. They also measured the electrical properties of their own gold films instead of reading them from a table. That precision does real work: it settles a standing argument about how temperature enters the Casimir force, and it tightens by a factor of three the limit on any new short-range force added to gravity between roughly 30 and 86 nanometres.
Connection
Chapter 2 stands on the fact that the vacuum is measured, not merely inferred, and this is that measurement at its sharpest — a sub-one-percent laboratory reading of a force that exists only because the zero-point field is there. It also shows what the precision buys: the same apparatus that weighs the vacuum becomes a search for physics beyond the standard model.
From the source
A micromechanical torsion oscillator determines the Casimir pressure between two gold-coated plates with a total relative error, at 95 percent confidence, of 0.19 percent at the shortest separation of 160 nanometres rising to 9.0 percent at 750 nanometres.Abstract; introduction, third improvement paragraph
Repeating the sweep 33 times at practically the same 293 separations, with a two-colour fibre interferometer that repositions the sample to within 0.2 nanometres, suppressed the random error below the systematic error — a dominance never previously achieved in a Casimir force experiment.Experimental procedure; Fig. 2 error curves
The electronic parameters of the gold films were obtained from the measured resistivity of companion films between 3 K and 400 K rather than from tables, giving a plasma energy of 8.9 eV and a relaxation parameter of 0.0357 eV at room temperature.Film characterisation paragraph, after Eq. (2)
Comparing the data with Lifshitz theory at 295 K, the Leontovich impedance approach agrees across the whole measured range, while the Drude-model approach — which predicts thermal effects of up to 16 percent of the pressure below one micrometre — is excluded at 95 percent confidence from 160 to 750 nanometres and at 99.9 percent confidence from 210 to 620 nanometres.Eqs. (3) and (4) and the following comparison paragraphs
The same data set the strongest existing constraints on a Yukawa correction to the Newtonian gravitational potential for interaction ranges from 29.5 to 86 nanometres, improving earlier limits by a factor of three near 40 nanometres.Eq. (5); Fig. 3, line 1
The small thermal corrections predicted by the competing calculations remain below the reach of this apparatus, so the measurement that would close the thermal Casimir question is one sensitive enough to resolve them at these separations.Closing comparison paragraph, before the summary
The way in
https://doi.org/10.1103/PhysRevD.75.077101How to cite it
R. S. Decca, D. López, E. Fischbach, G. L. Klimchitskaya, D. E. Krause, V. M. Mostepanenko (2007) Tests of new physics from precise measurements of the Casimir pressure between two gold-coated plates doi:10.1103/PhysRevD.75.077101