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Strange atomic bedfellows

Strange atomic bedfellows
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First Published: Thu, Sep 08 2011. 10 51 PM IST
Updated: Thu, Sep 08 2011. 10 51 PM IST
Think of them as estranged spouses, not implacable enemies. Think of them as clashing ideologies, like communism and capitalism, with common origins, diverging realities and converging fates. Superconductivity and magnetism are like that, bound and torn apart by the laws of physics.
Unlike most materials that resist the flow of electricity—think of water hitting a rock—superconductors allow current to flow through mostly unhindered. Many metals exhibit this ability, but they must be cooled to ultra-low temperatures. Lately, ceramics have stepped in at higher temperatures.
Superconductors repel magnetic fields, a phenomenon called the Meissner effect, which is put to good use in magnetically levitated or “floating” trains, such as the famous high-speed maglev (top operational speed: 461 kmph) link to Shanghai’s Pudong airport. This hostility to external magnetic fields is a notable hurdle in the development of new materials that hold the potential of new electronic uses, particularly the next generation of computer storage and memory.
Earlier this week, a team of physicists at Stanford University’s Institute for Materials and Energy Sciences, announced an advance that appeared to indicate superconductivity and magnetism could be bedfellows, however strange. They slapped a thin film of lanthanum aluminate on a bed of strontium titanate (both man-made materials that don’t conduct electricity except when supercooled) and found, to their surprise, superconductivity and a magnetic field on the edge of the infinitesimally small sandwich. How small? We’re talking four nanometers, as thin as a cell membrane, which is 1,000 times thinner than a human red-blood cell, itself invisible to the human eye.
The results of the study were published earlier this week in the journal Nature Physics, which also carried a paper from a Massachusetts Institute of Technology (MIT) team that used an alternative method to confirm magnetism and superconductivity do exist on the borders of the exotic sandwich.
This is a milestone, but it is not yet a route map to the destination of next-generation computing. “There is no immediate real-world application,” said Andrew Millis, a Columbia University physicist who wrote an essay in Nature Physics on the Stanford and MIT studies, when I asked him for the big picture. He compared the Stanford milestone with the “very early stages of the development of the transistor”, the fundamental building block of modern electronics.
The researchers have more immediate concerns, as the 28-year-old lead author of the Stanford study told me. “Our next step is to figure out whether the superconductivity and magnetism coexist within the material in an uneasy truce,” said Julie Bert, who participated in a “nano-fabrication” (building structures at atomic levels) winter-school programme at Bangalore’s Indian Institute of Science last year.
In other words, could it be for real? I asked the head of the group, Stanford physics professor Kathyrn A. Moler. “Is this a conventional superconductor that does not like magnetism, or is it an exotic kind of superconductor that likes magnetism?” Put another way, it isn’t clear if the superconductivity and magnetism are helping or fighting each other.
There are many questions ahead, but as with much of science, what appears like arcane incremental progress to the outside world still contains little eureka moments. As Bert explained, she and her colleagues were trying to see if voltage could be applied to control the superconductivity of the sandwich (similar to using voltage to control a silicon chip) when they found something else.
“The discovery of magnetism was a surprise to us,” confessed Bert.
“I came into the laboratory and Ms Bert showed me the data,” said Moler. “I said, there must be some mistake. What on earth is going on in those samples?”
Other researchers are trying to study what happens when an electrical field is applied to the sandwich or what happens if it is compressed. It isn’t yet known what physical properties contribute to the coexistence of magnetism and superconductivity in these materials.
“Now that we have discovered magnetism in this system, (it) offers even more exciting possibilities for engineering new materials,” said Bert. The possibilities are endless. Modern science allows scientists to create new materials, atomic layer by atomic layer, opening up myriad possibilities of varied, unanticipated properties.
For instance, in May, an MIT paper in Science revealed how the same sandwich of lanthanum aluminate and strontium titanate could be manipulated—at room temperature and with no superconducting properties—to work like a transistor, except cooler and faster than those in today’s silicon chips. Along the way, the process appeared to exhibit unknown physical properties of the material.
This is how the world of tomorrow will be built, idea by idea, atom by atom, much as ancient minds once believed. As the Greek philosopher Democritus once said: “Nothing exists except atoms and empty space. Everything else is opinion.”
Samar Halarnkar is editor-at-large, Hindustan Times and Mint. This is a fortnightly column that explores the cutting edge of science and technology. Comments are welcome at frontiermail@livemint.com
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First Published: Thu, Sep 08 2011. 10 51 PM IST