A Microscope That Spins Inside a Magnet express
A tiny needle glides over the surface like a finger over a page written in Braille. That's how a scanning tunneling microscope works: it feels the atomic landscape and turns bumps into a picture. But when you need to add a magnetic field, the design hits a wall. Usually, the field is directed perpendicular to the surface, like rain falling straight down. But what if you want to 'blow' from the side? Then you have to rebuild the microscope.
Engineers have assembled a new instrument the size of a walnut. It fits entirely inside a cylinder 37 mm in diameter — smaller than the width of a palm. Such a gap is almost always available inside a magnet. The microscope sits on a rotating platform, like a plate on the turntable in a microwave. Now the sample can be tilted at any angle to the magnetic field without removing it from the setup.
This flexibility opens the door to studying quantum materials. In these, electrons behave like a flock of birds: change the wind direction, and the whole flock turns. Previously, scientists could only see one angle of this flock. Now they can fly around it and view it from all sides.
Original abstract
as written by the authors arXiv:2603.01226
The Scanning Tunneling Microscope (STM) is a powerful instrument to study electronic density of states at surfaces down to atomic scale. Many interesting samples require studying variations as a function of the magnetic field, which is most often applied perpendicular to the surface. Conventional STM designs make it challenging to perform measurements when the magnetic field must be applied in other directions. Here we present a new STM setup installed on a rotatable platform. We have designed and built a new STM, which is small enough to allow for full rotation on a space with a diameter of 37 mm, well below the available space within many magnets. We show that the new rotatable STM setup preserves the performance of state-of-the-art STMs in terms of noise and accuracy. Our new approach significantly enhances control over the direction of the applied magnetic field and opens exciting new possibilities to study quantum materials.
A diameter of 37 mm is about the size of a tennis ball. The entire microscope, with its precise positioning system, fits into that volume.
Science fiction often features probes that scan the surfaces of alien planets. This microscope is their downscaled-to-atomic-scale version, capable of operating in a strong magnetic field.