Quantum microscope: Researchers observe electrons during the quantum leap


So far, atomically precise scanning tunneling microscopes have not been able to image the fast electron movements in individual molecules. Researchers at the Max Planck Institute for Solid State Research in Stuttgart combined scanning tunneling microscopy with fast laser pulses of just a few attoseconds (billionths of a billionth of a second). In one attosecond, a ray of light can just traverse one water molecule.

Electrons excited in this way can be detected more quickly and also offer opportunities for processor development.

A scanning tunneling microscope guides a fine tip over the surface of the sample at a distance of a few nanometers. A voltage is applied between the sample and the measuring tip. Although the electrons cannot mathematically overcome the path from the sample to the tip, they still appear there due to the quantum mechanical tunnel effect, which means that a small current can be measured. Because the tunnel effect decreases exponentially with distance, the topography of the sample can be determined with atomic precision using this technique.

The new quantum microscope excites the electrons in the molecule with fast laser pulses and thus makes it possible to observe the movements of electrons in the molecule at much shorter distances. In addition, the ultra-short laser pulses stimulated the electrons to jump between the different orbitals of an atom. These quantum leaps could also be tracked in the tunnel current. With repeated measurements and time-varying laser pulses, the researchers recorded series of images that reproduce the behavior of electrons in a molecule with atomic precision.

The new technology not only makes it possible to observe molecules in a chemical reaction with atomic precision and to see how electrons rearrange themselves to form new chemical bonds. It will also be possible to track electrons as they move through processors and computer chips. In addition, the new technology can also accelerate the charge carriers considerably. Klaus Kern, Director at the Max Planck Institute for Solid State Research says: “With ultra-short flashes of light, the frequency at which electrons oscillate can possibly be increased from the gigahertz range to one quadrillion hertz (petahertz).” In this way, processor technology could be accelerated millions of times.


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