The lead author of the study to be published in Nature, Dr Andrea Cavalleri at the Oxford University Department of Physics, said: ‘We’ve all seen how a stick in a pond appears to be at a different angle depending on whether we look at it from outside or inside the water. At a microscopic level, this effect depends on how stiff atomic bonds are and with how much delay atoms and electrons respond when they are placed in the rapidly wiggling electric field of light.
‘If you want to understand the propagation of light at microscopic level, especially in some the complex materials that are of interest for modern opto-electronic applications, you need to make a ‘molecular movie’ of how the atoms and electrons wiggle in the light field. To do so, you need to find a camera with an extremely quick shutter speed – that of a handful of femtoseconds (which is less than one thousandth of a billionth of a second).
‘This very fast timescale can be reached with modern laser technology – but lasers can’t see where the constituents atoms actually are. If you want to see this ‘shape’ of a molecule you need x-rays, but there are currently no x-rays beams with short enough pulses to take snapshots of atomic motions.
‘What we have managed to do is combine ultrafast laser pulses with electron beams in a particle accelerator, deflecting a small slice of the long electron pulse on a separate orbit of the accelerator. Thus, these electrons radiated short enough x-ray pulses to measure elementary atomic motions on the femtosecond timescale. This enabled us to measure the motion of charged atoms on the ultra fast timescale with an accuracy of less than one thousandth of one billionth of a meter. This means we are capable of resolving in time the displacements of atoms by less than one atomic nucleus.
‘This technology can now be applied to other elementary processes at the microscopic level, and we can measure their displacements with unprecedented speed and resolution.’
Barbara Hott | alfa
Heating quantum matter: A novel view on topology
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A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
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