Today's electron microscopes achieve outstanding resolutions and can image details on an atomic scale. However, they are not suitable for sensitive materials such as biological samples. When sensitive biological molecules are bombarded with high-energy electron beams, they are quickly destroyed.

Philipp Haslinger works in the field of quantum and matter wave optics. In his work over the past few years, he has discovered a way to radically expand the capabilities of electron microscopy. His idea is to use electrons as “miniature magnetic sensors,” so to speak, to measure the quantum physical properties of a sample in a gentle, non-destructive manner with high precision, similar to how an MRI can be used to measure the inside of the human body. To advance this technology, Philipp Haslinger is now receiving a Consolidator Grant from the European Research Council (ERC).

Electron beams and electron spins

“We are combining two technologies that were previously considered completely separate,” says Philipp Haslinger. “On the one hand, electron microscopy, and on the other, magnetic resonance spectroscopy.” The two techniques have very different strengths: Electron microscopy achieves resolutions in the nanometer range, while magnetic resonance has a lower resolution but can distinguish between different quantum states with high sensitivity.

In a conventional electron microscope, electrons perform the same task as light in a conventional light microscope: the sample is “illuminated” with electrons, the electrons are scattered and measured, and an image is then generated from this data.

However, Haslinger's team views electrons from a quantum physics perspective: according to the laws of quantum physics, electrons move in waves – similar to water waves that are reflected at the edge of a swimming pool and can overlap with themselves. By measuring these overlaps, it is possible to obtain information about how the electron interacts with the matter it passes by. “The particles in the material have quantum spins – an intrinsic angular momentum that also generates a tiny magnetic field,” says Philipp Haslinger. “We can measure this magnetic field with the electrons – and with a factor of 1000 better than before.”

The measurement is carried out in two steps: First, the sample is excited. Microwaves – i.e., a very gentle method – are used to influence the magnetic spins of the sample. Then the electron beam is used to “collect” the spin information from the sample surface or to look inside the sample. “Simulations show that this technique has great potential,” says Philipp Haslinger. “We are very confident that we will be able to produce high-precision images using the new method in the next few years.”