Scientists have confirmed a brand new form of matter: time crystals
For months now, there’s been speculation that researchers might have finally created time crystals – strange crystals that have an atomic structure that repeats not just in space, but in time, putting them in perpetual motion without energy.
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>>putting them in perpetual motion without energy.
I’m not reading that article.
Peak Warming Man said:
>>putting them in perpetual motion without energy.I’m not reading that article.
It is not a great piece.
Try this
https://www.technologyreview.com/s/602541/physicists-create-worlds-first-time-crystal/
Anyway it’s all very interesting
dv said:
Peak Warming Man said:
>>putting them in perpetual motion without energy.I’m not reading that article.
It is not a great piece.
Try this
https://www.technologyreview.com/s/602541/physicists-create-worlds-first-time-crystal/
I have to read each paragraph three times to understand what the heck they’re trying to say. It would be easier to understand if they used longer words, words like anisotropy, glass transition, quasicrystal, hysteresis, molecular rotor, natural frequency.
Am I right in thinking that all they have demonstrated is that a ring of ytterbium ions, placed so that the spin of one ion changes the spin of the next, has a natural frequency of spin flipping?
mollwollfumble said:
dv said:
Peak Warming Man said:
>>putting them in perpetual motion without energy.I’m not reading that article.
It is not a great piece.
Try this
https://www.technologyreview.com/s/602541/physicists-create-worlds-first-time-crystal/
I have to read each paragraph three times to understand what the heck they’re trying to say. It would be easier to understand if they used longer words, words like anisotropy, glass transition, quasicrystal, hysteresis, molecular rotor, natural frequency.
Am I right in thinking that all they have demonstrated is that a ring of ytterbium ions, placed so that the spin of one ion changes the spin of the next, has a natural frequency of spin flipping?
Ah, wait. I told you I have to read each paragraph three times to understand it. When a single spin is flipped by a laser, this changes the spin of the two adjacent ions, so the wave would be expected to propagate symmetrically in both directions. But in order to exhibit a natural frequency, the spin flipping has to propagate in only a single direction. So a wave of changes that is driven symmetrically in both directions is morphing into one that propagates only in a single direction. So yes, this can be considered symmetry-breaking in time.
It could be that the ytterbium ion in the ring opposite the driver receives two opposite “change spin” signals very nearly simultaneously, so must decide which way to flip, and the way that this atom decides to flip determines the direction around the circle that builds up into a unidirectional clockwise or anticlockwise motion.
mollwollfumble said:
Ah, wait. I told you I have to read each paragraph three times to understand it. When a single spin is flipped by a laser, this changes the spin of the two adjacent ions, so the wave would be expected to propagate symmetrically in both directions. But in order to exhibit a natural frequency, the spin flipping has to propagate in only a single direction. So a wave of changes that is driven symmetrically in both directions is morphing into one that propagates only in a single direction. So yes, this can be considered symmetry-breaking in time.
It could be that the ytterbium ion in the ring opposite the driver receives two opposite “change spin” signals very nearly simultaneously, so must decide which way to flip, and the way that this atom decides to flip determines the direction around the circle that builds up into a unidirectional clockwise or anticlockwise motion.
I’ve had a modification on that thought. Suppose adjacent spins of ytterbium ions want to be antiparallel (same axis but opposite spin direction) and suppose that there are an odd number of atoms in the ring. Then there will always have to be what is effectively a magnetic domain boundary part way around the ring, ie. there must be at least one atom with wrongly aligned spin.
Then what would happen with the laser driver would depend on whereabouts on the ring that domain boundary was relative to the driving pulse. If opposite the laser pulse then not much would happen, but elsewhere and the laser pulse would set the magnetic domain boundary spinning around the ring at its natural frequency. The naural period would be the time for one atom to flip the adjacent atom’s spin times the number of atoms in the ring.