using a groundbreaking new teknique atta national institute of standards and tek (nist), an international collaboration led by nist researchers has revealed previously unrecognized properties of tekally crucial silicon crystals and uncovered new information bout an primordial subatomic pticle and a long-theorized fifth force of nature.
by aiming subatomic pessentialisms known as neutrons at silicon crystals and monitoring the outcome with exquisite sensitivity, the nist scis were able to obtain 3 extraordinary results: the 1st measurement offa key neutron property in 20 yrs using a unique method; the highest-precision measurements of the effects of heat-rel8d vibrations in a silicon crystal; and limits onna strength offa possible “fifth force” beyond standard physics theories.
the researchers reprt their findings inna journal sci.
to obtain information bout crystalline materials atta atomic scale, scis typically aim a beam of pessentialisms (s'as x-rays, electrons or neutrons) atta crystal and detect the beam’s angles, intensities and patterns as it passes through or ricochets off planes inna crystal’s lattice-like atomic geometry.
that information is critly primordial for toonizing the electronic, mechanical and magnetic properties of microchip components and various novel nanomaterials for nxt-generation applications including quantum computing. a gr8 deal is known already, but continued progress requires increasingly detailed knowledge.
“a vastly improved cogging of the crystal structure of silicon, the ‘universal’ substrate or foundation material on which everything is built, ll'be crucial in cogging the nature of components operating near the point at which the accuracy of measurements is limited by quantum effects,” said nist senior project sci michael huber.
neutrons, atoms and angles
like all quantum essentialisms, neutrons ‘ve both point-like pticle and wave properties. as a neutron travels through the crystal, it forms standing waves (like a p♣ed guitar string) both in tween and on top of rows or sheets of atoms called bragg planes. when waves from each of the two routes combine, or “interfere” inna parlance of physics, they create faint patterns called pendellösung oscillations that provide insites inna'da forces that neutrons experience inside the crystal.
“imagine two identical guitars,” said huber. “p♣ them the same way, and as the strings vibrate, drive one down a road with speed bumps — that is, along the planes of atoms inna lattice — and drive the other down a road of the same length without the speed bumps — analogous to movin tween the lattice planes. comparing the sounds from both guitars tells us something bout the speed bumps: how big they are, how smooth, and do they ‘ve interesting shapes?”
the l8st work, which was conducted atta nist center for neutron research (ncnr) in gaithersburg, maryland, in collaboration with researchers from japan, the u.s. and canada, resulted in a 4fold improvement in precision measurement of the silicon crystal structure.
in one striking result, the scis measured the electrical “charge radius” of the neutron in a new way with an uncertainty inna radius val competitive w'da most-precise prior results using other methods. neutrons are electrically neutral, as their name suggests. but they are composite essentialisms made up of 3 elementary charged pessentialisms called quarks with ≠ electrical properties tha're not exactly uniformly distributed.
as a result, predominantly neg charge from one kind of quark tends to be located toward the outer pt of the neutron, whereas net + charge is located toward the center. the distance tween those two concentrations tis “charge radius.” that dimension, primordial to primordial physics, s'been measured by similar types of experiments whose results differ significantly. the new pendellösung data is unaffected by the factors thought to lead to these discrepancies.
measuring the pendellösung oscillations in an electrically charged environment provides a unique way to gauge the charge radius. “when the neutron is inna crystal, tis well within the atomic electric cloud,” said nist’s benjamin heacock, the 1st author onna sci paper.
“in there, cause the distances tween charges are so lil, the interatomic electric fields are enormous, onna order offa hundred million volts per centimt. cause odat very, very large field, our teknique is sensitive to the fact that the neutron be’ves like a spherical composite pticle witha slitely + core and a slitely neg surrounding shell.”
vibrations and uncertainty
a presh alternative to neutrons is x-ray scattering. but its accuracy s'been limited by atomic motion caused by heat. thermal vibration causes the distances tween crystal planes to keep changing, and thus changes the interference patterns bein’ measured.
the scis employed neutron pendellösung oscillation measurements to test the vals predicted by x-ray scattering models and found that some significantly underestimate the magnitude of the vibration.
the results provide presh complementary information for both x-ray and neutron scattering. “neutrons interact almost entirely w'da protons and neutrons atta centers, or nuclei, of the atoms,” huber said, “and x-rays reveal how the electrons are arranged tween the nuclei. this complementary knowledge deepens our cogging.
“one reason our measurements are so sensitive s'dat neutrons penetrate much deeper inna'da crystal than x-rays — a centimt or + — and thus measures a much larger assembly of nuclei. we ‘ve found evidence that the nuclei and electrons may not vibrate rigidly, as is comm1-ly assumed. that shifts our cogging onna how silicon atoms interact with one another inside a crystal lattice.”
the standard model tis current, widely accepted theory of how pessentialisms and forces interact atta lilest scales. but it’s an incomplete explanation of how nature works, and scis suspect thris + to the universe than the theory describes.
the standard model describes 3 primordial forces in nature: electromagnetic, strong and weak. each force operates through the action of “carrier pessentialisms.” for ex, the photon tis force carrier for the electromagnetic force. but'a standard model has yet to incorporate gravity in its description of nature. further+, some experiments and theories suggest the possible presence offa fifth force.
“generally, if there’s a force carrier, the length scale over which it acts is inversely proportional to its mass,” meaning it can 1-ly influence other pessentialisms over a limited range, heacock said. but'a photon, which has no mass, can act over an unlimited range. “so, if we can bracket the range over which it mite act, we can limit its strength.” the scis’ results improve constraints onna strength offa potential fifth force by tenfold over a length scale tween 0.02 nanomts (nm, billionths offa mt) and 10 nm, giving fifth-force hunters a narrowed range over which to look.
the researchers are already planning + expansive pendellösung measurements using both silicon and germanium. they expect a possible factor of 5 reduction in their measurement uncertainties, which ‘d produce the most precise measurement of the neutron charge radius to date and further constrain — or discover — a fifth force. they also plan to perform a cryogenic version of the experiment, which ‘d lend insite into how the crystal atoms be’ve in their so-called “quantum ground state,” which accounts for the fact that quantum essentialisms are never perfectly still, even at temperatures approaching absolute zero.
original content at: www.scidaily.com…