Electrons as a ruler for crystal structure – published in Physical Review Letters

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We demonstrate that electrons inside a crystal driven by ultrashort and intense laser pulses act as an extremely precise ruler for the crystal’s electronic structure. When subjected to the optical field of the laser pulses, the electrons navigate through the crystal on a timescale of a single femtosecond – one million times faster than the motion of electrons in computer chips. Under these extreme conditions electrons reveal their quantum wave nature, which allows them to sense the energy landscape provided by the crystal with unprecedented precision. Leveraging this phenomenon, we developed a new technique to map out the electronic structure of the 2D material graphene. It is like a marble rolling over an unknown surface and depending on the height of this landscape the marble changes its color. Based on the color that the marble takes on at the end of its journey, we can read out what the landscape it passed through looked like. In graphene we use this principle to detect the quantum phase of electrons, akin to the marble’s color. This method not only sheds light on the fundamental behavior of electrons as quantum mechanical particles but we anticipate that in the future it will enable us to observe rapid changes of the crystal structure toward entirely new states of matter with purpose-tailored quantum properties for technological applications.

These results were published in Physical Review Letters here. An open access version can be found here on arXiv.