This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Despite all the advertisements for engagement rings and necklace gifts, natural diamonds are imperfect. Their carbon atoms are arranged in a cubic lattice, but they nonetheless contain several types of crystallographic defects due to impurities that occasionally replace a carbon atom.
The most common types of impurities are nitrogen and boron; "Type I" diamonds contain nitrogen impurities, which can be isolated or clustered, at concentrations of up to 1%, and make up about 95% of all natural diamonds. More specifically, some diamonds have a nitrogen-vacancy (NV) impurity. A nitrogen atom replaces one carbon atom, and adjacent to it is an empty lattice spot.
One type of solid-state clock, a diamond clock, uses this feature to measure time, as the defect has optical and nuclear spin states that can be manipulated with microwaves and other light. But the NV energy levels are strongly modified by temperature. Now a group of researchers from the U.S. and Germany has developed a way to overcome this limitation.
Their work is published in the journal Physical Review Applied. All modern atomic clocks work by confining atoms in laser traps or vapor cells. A clock based on a solid-state material does away with the need to trap atoms, offering a more robust clock that is easier to fabricate and integrate with modern electronics.
Such a material may even offer a higher density of emitters, with perhaps an Avogadro's number of emitters in kilogram-scale crystals. NV centers in diamond have an energy ground state that is slightly split, akin to the well-known sodium D lines that appear bright yellow but are slightly split in energy levels, called a "doublet." As electrons transfer from sodium's two 3p energy levels to the 3s energy level, the atom emits yellow light of slightly different wavelengths. The difference is 0.597 nanometers, which corresponds to a frequency difference of 515 gigahertz (GHz).
For NV centers, the ground-state splitting from different electron spins is 2.87 GHz, a quantity the scientists call D. This can, in fact, serve as a precise diamond clock transition, especially since diamonds are so stable. However, this transition is sensitive to magnetic and electric fields, strain and, in particular, temperature, with the D-only clock having a temperature sensitivity of 25.3 ppb/mK (parts per billion per millikelvin).
Extract — continue reading at the source.
