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article imageTracking time without using a clock

By Tim Sandle     Feb 16, 2017 in Science
Researchers have measured the time delay in electron photoemission without using a clock (a very tiny fraction of time). This carries importance for developing cutting-edge technology.
The different approach for tracking time has come from École polytechnique fédérale de Lausanne researchers and it concern's measuring a physical phenomenon called “photoemission.” This effect describes what appends when light is shone on certain materials and electrons are emitted. This effect is the basis of laser technology.
What the French researchers have done is to calculate a delay of one billionth of one billionth of a second in photoemission. This came from the measurement of electrons that were photo-emitted from a crystal of copper. They have achieved this not through conventional time measurements but by measuring the spin of photoemitted electrons without the need of ultrashort laser pulses.
The reason why this matters is because photoemission is the basis of cutting-edge spectroscopy techniques. These methods are used to study the properties of electrons in a solid, and understanding this reveals the magnetic properties of different materials and this furthers the development of consumer and medical electronic devices.
While the measured a time delay on the scale of attoseconds (very tiny fractions of seconds), understanding this and the variations with different materials provides a benchmark for developing different electronic switches. The most important materials to understand better are graphene and high-temperature superconductors, where understanding more fully the photoemission process should advance the properties of these materials and help with the development of electronic devices.
The research is published in the journal Physical Review Letters Physical Review Letters, under the title "Spin polarization and attosecond time delay in photoemission from spin degenerate states of solids."
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