Optomechanical systems are nothing if not delicate. When the driving force (very literally) in a system is the pressure of incident light it is no surprise that forces being examined are on a minute scale. On a relevant diversion: the Nobel prize for physics has recently been announced to be for the discovery of gravitational waves which was where the development of optomechanics came from. The effects of optomechanics on the interferometric gravitational wave detectors had to be accounted for to analyse when the disturbance was actually caused by a gravitational wave. Now back to pure optomechanics. The sensitivity of electromechanical systems, which makes them so hard to set up, can actually be used as an advantage. All the best measuring equipment is delicate purely because it needs to be delicate to pick up the change its supposed to be measuring and this is where optomechancial systems can shine.
Although radioactive dating is often talked about another, no less important type of dating, luminescence dating, is not. Luminescence dating is used to study the last time a piece of rock was in the sunlight. It can only be used on materials seen as semiconductors, mainly quartz and feldspar as these both contain silicon, but if the date these rocks were buried is known then the date of the surroundings is also known. The dating works by looking at the number of trapped electrons present in the rock. You see crystal lattices can develop defects which in this case are called electron traps. As various radioactive decays occur in the rocks around them the ionising radiation produces electron-hole pairs within the lattice. The holes exist in the valence band and electrons exist in the conduction band and these electrons also can get trapped in the interband region caused by the defect. These electrons can then be released when light is shone upon the rock and so we can learn how long it has been in the ground based on the amount of charged stored within it.
In 2014 the Nobel prize for physics was given to three men whose combined work was the production of a blue light emitting diode. The reason that this was such a special achievement was the fact that when the blue LED is covered by a colour conversion layer made of various phosphors it can have an eventual output of white light. This is obviously ideal for almost all artificial lighting as white light is mirrors that which is produced by the Sun. Phosphors in general work by absorbing the incident blue light and then radiating light of a lower frequency through the promotion and relaxation of atomic electrons. However there is a problem. Although LEDs have only improved in reliability, energy efficiency and lifetime over the course of their development the phosphors used have remained limited to rare earth metals and their ions.
Interesting fact: It is very likely that your mobile phone contains a battery which could explode quite vigorously if heated too much. In order to prevent this occurrence, as it would surely be quite a downer on sales, every phone is designed with a temperature control component. I think this is quite a good analogy for a single chip. Much like phones there is constant pressure to put more and more components on each single chip, each of which must produce a certain amount of heat. To make sure that electronic chips can continue on this trend of being ever more compact it is essential to be able to monitor and control the temperature of individual chips.
I have previously written about birds and their uncanny ability to know what direction north is here. Both that and this post are both on the topic of birds’ ability to see magnetic fields probably caused by a magnetically sensitive cell in the eye. But the exact nature of this magnetoreception is still unknown. The two main theories are that either a iron containing particle could interact with the magnetic field to aid navigation or perhaps that light induced radical pairs of electrons could have their spins slightly biased based on a ever present magnetic field. This second idea is the one that is examined more closely as if the theory is true the mechanism would be quantum mechanical in many ways.
In the past I have written about carbon nanodots here. Quantum dots are a more general kind of carbon dot as quantum dots can be made of any semiconductor. Semiconductors in general have a unique band structure which results in the confining of their electrons. Quantum dots have their own unique energy levels which electrons are trapped in very similar to the nucleus of an atom. Because of this quantum dots are also known as artificial atoms. As a result a double quantum dot, where two quantum dots are coupled, can be seen as a molecule.
One of graphite’s most important properties is its ability to conduct electricity. The fact that the carbon atoms have formed three of the possible four bonds each leaves many electrons free to move and carry their charge. In graphene the same logic applies except more care has to be taken looking into the source of resistance. Complex scattering processes occur in graphene due to its 2D nature. These combine to produce the resistivity observed.