Slashdot Mirror
Scientists Discover a 'Tuneable' Novel Quantum State of Matter (phys.org)
An anonymous reader quotes a report from Phys.Org: An international team of researchers led by Princeton physicist Zahid Hasan has discovered a quantum state of matter that can be "tuned" at will -- and it's 10 times more tuneable than existing theories can explain. This level of manipulability opens enormous possibilities for next-generation nanotechnologies and quantum computing. Hasan and his colleagues, whose research appears in the current issue of Nature, are calling their discovery a "novel" quantum state of matter because it is not explained by existing theories of material properties. The classical phases of matter -- solids, liquids and gases -- arise from interactions between atoms or molecules. In a quantum phase of matter, the interactions take place between electrons, and are much more complex.
[Hasan] and his colleagues arranged atoms on the surface of crystals in many different patterns and watched what happened. They used various materials prepared by collaborating groups in China, Taiwan and Princeton. One particular arrangement, a six-fold honeycomb shape called a "kagome lattice" for its resemblance to a Japanese basket-weaving pattern, led to something startling -- but only when examined under a spectromicroscope in the presence of a strong magnetic field [...]. All the known theories of physics predicted that the electrons would adhere to the six-fold underlying pattern, but instead, the electrons hovering above their atoms decided to march to their own drummer -- in a straight line, with two-fold symmetry. The decoupling between the electrons and the arrangement of atoms was surprising enough, but then the researchers applied a magnetic field and discovered that they could turn that one line in any direction they chose. Without moving the crystal lattice, [one] could rotate the line of electrons just by controlling the magnetic field around them.
[Hasan] and his colleagues arranged atoms on the surface of crystals in many different patterns and watched what happened. They used various materials prepared by collaborating groups in China, Taiwan and Princeton. One particular arrangement, a six-fold honeycomb shape called a "kagome lattice" for its resemblance to a Japanese basket-weaving pattern, led to something startling -- but only when examined under a spectromicroscope in the presence of a strong magnetic field [...]. All the known theories of physics predicted that the electrons would adhere to the six-fold underlying pattern, but instead, the electrons hovering above their atoms decided to march to their own drummer -- in a straight line, with two-fold symmetry. The decoupling between the electrons and the arrangement of atoms was surprising enough, but then the researchers applied a magnetic field and discovered that they could turn that one line in any direction they chose. Without moving the crystal lattice, [one] could rotate the line of electrons just by controlling the magnetic field around them.
All the known theories of physics predicted that the electrons would adhere to the six-fold underlying pattern, but instead, the electrons hovering above their atoms decided to march to their own drummer -- in a straight line, with two-fold symmetry. The decoupling between the electrons and the arrangement of atoms was surprising enough, but then the researchers applied a magnetic field and discovered that they could turn that one line in any direction they chose. Without moving the crystal lattice, [one] could rotate the line of electrons just by controlling the magnetic field around them.
Sounds classical to me:
- The layout of the substrate produced a planar potential well with no, or very little, difference of energy for electrons being in one position vs. another.
- Provided the average density of the electrons was right, they behaved like a gas of individual particles in a thin container, or marbles on a flat surface.
- The electrons repelled each other, so they tended to spread out evenly. (Spread out too far, though, and they leave some positive-charged substrate behind. So they don't just fly apart and go away.)
- But electrons also have spin, which means they are little magnets. So, with their mutual repulsion largely defeated by forces holding them at a given average spacing, they tend to line up north-pole-to-south-pole in strings (but don't all pile up because coming more than a little closer together under the slight magnetic attraction is balanced by higher repulsion.) The strings are a bit more dense than the average gas, so most of the electrons join one and reduce their total energy.
- So now you have these long magnetic strings, with no preferred orientation driven by irregularities in the substrate. Bring a magnet nearby and they'll line up with its field while spacing out by mutual magnetic AND electrostatic repulsion, much like iron filing lines.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
The most exciting phrase to hear in science, ... is not “Eureka!” (I found it!) but “That’s funny ” ...
Interestingly, they tie as least exciting phrase to hear in bed.
It must have been something you assimilated. . . .
Are used as a matter of simplification. There is no clean boundary, only a continuum where the classical states (solid, liquid, gas, plasma) are specific islands.
Quantum doesn't mean magical, it just means something with discrete states rather than continuous states. QM is a quantum theory that mostly applies to the very small but can scale up to objects of a few millimetres under some conditions. Actually, some aspects - such as the Schrodinger Equation - applies to planetary rings, asteroid belts and accretion disks.
The first question is whether it's useful to talk of states of matter. If it is, is it useful to use traditional ones or should we decompose phenomena into the raw properties and then compose a new set of states that reduces the need for weird overlaps and talk of mysteries beyond the ken of man?
The second question (or third, if you go with the option above) is whether something that is apparently orthogonal to the original list is a state in the original sense? The original sense is a linear continuum, not a set of sets. This new thing is apparently not on that line. If matter's state is multidimensional, our naming should reflect that.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
"Religion discovers new..."
Fun fact: Historically, the Catholic Church has been a major sponsor of astronomy. Catholic Church backed and help make plenty of scientific discoveries. They have had poor reactions to some discoveries but contributed a lot to making them.
Anons need not reply. Questions end with a question mark.