« ~You know I like to die for awhile / Everyday in the afternoon~ | Main | ~So I'm writing everything down in a spiral notebook~ »
July 15, 2006
"We cannot learn the cipher / That's writ upon our cell, / Stars help us by a mystery / Which we could never spell."
Spinons and holons have been observed for the first time. This is big for the sort of technology in Hacking Matter, I think.
Just as the body and wheels of a car are thought to be intrinsic parts of a whole, incapable of separate and independent actions, i.e., the body goes right while the wheels go left, so, too, are electrical charge and spin intrinsic components of an electron. Except, according to theory, in one-dimensional solids, where the collective excitation of a system of electrons can lead to the emergence of two new particles called “spinons” and “holons.” A spinon carries information about an electron’s spin and a holon carries information about its charge, and they do so as separate and independent entities. Numerous experiments have tried to confirm the creation of spinons and holons, referred to as spin-charge separation, but it took the technological advantages offered at ALS Beamline 7.0.1, also known as the Electronic Structure Factory (ESF), to achieve success.
In a paper published in the June 2006 issue of the journal Nature-Physics, researchers have reported the observation of distinct spinon and holon spectral signals in one-dimensional samples of copper oxide, SrCuO2, using the technique known as ARPES, for angle-resolved photoemission spectroscopy.
The idea behind spin-charge separation is that electrons behave differently when their range of motion is restricted to a single dimension, as opposed to three or even two dimensions. When moving through one dimension, for example, the electrons are lined up head-to-tail, making the repulsive force between their negative electrical charges overridingly dominant. The restricted movement of electrons through one-dimensional material was expected to give rise to collective effects that would be strong enough to break the information flow of spin and charge from a single electron.
ARPES is an excellent tool for observing spin-charge separation and other collective effects involving electrons. In this technique, x-rays are flashed on a sample causing electrons to be emitted through the photoelectric effect. Measuring the kinetic energy of emitted electrons and the angles at which they are ejected identifies their velocity and scattering rates. This in turn yields a detailed picture of the electron energy spectrum. Ordinarily, the removal of an electron from a crystal creates a hole, a vacant positively-charged energy space. This hole carries information on both the spin and the charge, as observed in a single peak of an ARPES spectrum. If spin-charge separation occurs, the hole decays into a spinon and a holon and two peaks in the ARPES spectrum are observed.
ALS Beamline 7.0.1 utilizes a state-of-the-art undulator magnetic insertion device to generate beams of x-rays with properties similar to that of a laser. These coherent and tunable x-ray beams are a hundred million times brighter than those from the best x-ray tubes and provide an exceptionally high degree of angular resolution for ARPES experiments.
Another area in which spinons and holons could play an important role is in the development of nanowires, one-dimensional hollow tubes through which the movement of electrons is so constrained that quantum effects dominate.
Nanowires are expected to be key components in future nanotechnologies, including optoelectronics, biochemical sensing, and thermoelectrics.
The creation of spinons and holons in one-dimensional systems is also expected to have an impact on the future of spintronics, a technology in which the storage and movement of data will be based on the spin of electrons, rather than just on charge, as with our current electronic technology.
Thanks to Uncle Sam, there are a bunch of pretty pretty rare old star charts available online at really high resolutions that are great for desktop backgrounds. via
I should really have reversed those two links, so the ultra-nifty sky maps didn't get lost in all the gibberish about electrons and spinons and holons and, as Monty Burns would say, "other nuclear bric-a-brac." Oh well.
Of course, when I say "gibberish," I mean it lovingly, following the dubious etymology laid forth by Samuel Johnson in his "Plan of an English Dictionary":
The present usage of spelling, where the present usage can be distinguished, will, therefore, in this work, be generally followed; yet there will be often occasion to observe, that it is in itself inaccurate, and tolerated rather than chosen; particularly when, by the change of one letter or more, the meaning of a word is obscured, as in farrier for ferrier, as it was formerly written, from ferrum, or fer; in gibberish for gebrish, the jargon of Geber, and his chymical followers, understood by none but their own tribe.
Geber was none other than Jabir ibn Hayyan, the father of (al)chemistry.
Jabir is mostly known for his contributions to chemistry. He emphasised systematic experimentation, and did much to free alchemy from superstition and turn it into a science. He is credited with the invention of many types of now-basic chemical laboratory equipment, and with the discovery and description of many now-commonplace chemical substances and processes – such as the hydrochloric and nitric acids, distillation, and crystallisation – that have become the foundation of today's chemistry and chemical engineering.
His books strongly influenced the medieval European alchemists and justified their search for the philosopher's stone.
In spite of his leanings toward mysticism (he was considered a Sufi) and superstition, he more clearly recognised and proclaimed the importance of experimentation. "The first essential in chemistry", he declared, "is that you should perform practical work and conduct experiments, for he who performs not practical work nor makes experiments will never attain the least degree of mastery."
Jabir is also credited with the invention and development of several chemical instruments that are still used today, such as the alembic, which made distillation easy, safe, and efficient. By distilling various salts together with sulfuric acid, Jabir discovered hydrochloric acid (from salt) and nitric acid (from saltpeter). By combining the two, he invented aqua regia, one of the few substances that can dissolve gold. Besides its obvious applications to gold extraction and purification, this discovery would fuel the dreams and despair of alchemists for the next thousand years. He is also credited with the discovery of citric acid (the sour component of lemons and other unripe fruits), acetic acid (from vinegar), and tartaric acid (from wine-making residues).
Jabir applied his chemical knowledge to the improvement of many manufacturing processes, such as making steel and other metals, preventing rust, engraving gold, dyeing and waterproofing cloth, tanning leather, and the chemical analysis of pigments and other substances. He developed the use of manganese dioxide in glassmaking, to counteract the green tinge produced by iron — a process that is still used today. He noted that boiling wine released a flammable vapor, thus paving the way to Al-Razi's discovery of ethanol.
The seeds of the modern classification of elements into metals and non-metals could be seen in his chemical nomenclature. He proposed three categories: "spirits" which vaporise on heating, like camphor, arsenic, and ammonium chloride; "metals", like gold, silver, lead, copper, and iron; and "stones" that can be converted into powders.
Several technical terms introduced by Jabir, such as alkali, have found their way into various European languages and have become part of scientific vocabulary.
Jabir's alchemical investigations revolved around the ultimate goal of takwin — the artificial creation of life. Alchemy had a long relationship with Shi'ite mysticism; according to the first Imam, Ali ibn Abi Talib, "alchemy is the sister of prophecy". Jabir's interest in alchemy was probably inspired by his teacher Ja'far al-Sadiq, and he was himself called "the Sufi", indicating that he followed the ascetic form of mysticism within Islam.
In his writings, Jabir pays tribute to Egyptian and Greek alchemists Hermes Trismegistus, Agathodaimon, Pythagoras, and Socrates. He emphasises the long history of alchemy, "whose origin is Arius ... the first man who applied the first experiment on the [philosopher's] stone... and he declares that man possesses the ability to imitate the workings of Nature" (Nasr, Seyyed Hossein, Science and Civilization of Islam).
Jabir states in his Book of Stones (4:12) that "The purpose is to baffle and lead into error everyone except those whom God loves and provides for". His works seem to have been deliberately written in highly esoteric code, so that only those who had been initiated into his alchemical school could understand them. It is therefore difficult at best for the modern reader to discern which aspects of Jabir's work are to be read as symbols (and what those symbols mean), and what is to be taken literally. Because his works rarely made overt sense, the term gibberish is believed to have originally referred to his writings (Hauck, p. 19).
Jabir's alchemical investigations were theoretically grounded in an elaborate numerology related to Pythagorean and Neoplatonic systems. The nature and properties of elements was defined through numeric values assigned the Arabic consonants present in their name, ultimately culminating in the number 17.
To Aristotelian physics, Jabir added the four properties of hotness, coldness, dryness, and moistness (Burkhardt, p. 29). Each Aristotelian element was characterised by these qualities: Fire was both hot and dry, earth cold and dry, water cold and moist, and air hot and moist. This came from the elementary qualities which are theoretical in nature plus substance. In metals two of these qualities were interior and two were exterior. For example, lead was cold and dry and gold was hot and moist. Thus, Jabir theorised, by rearranging the qualities of one metal, based on their sulfur/mercury content, a different metal would result. (Burckhardt, p. 29) This theory appears to have originated the search for al-iksir, the elusive elixir that would make this transformation possible — which in European alchemy became known as the philosopher's stone.
Jabir also made important contributions to medicine, astronomy, and other sciences. Only a few of his books have been edited and published, and fewer still are available in translation. The Geber crater, located on the Moon, is named after him.
Posted by Jon Rubin at July 15, 2006 11:01 PM
Trackback Pings
TrackBack URL for this entry:
http://www.ubiquit.us/movabletype/mt-tb.cgi/210