Nanowire Project

Investigator: Ifan Hughes
Co-Investigator: Charles Adams
Post-Doctoral Research Associate: Kevin Weatherill
PhD Student: Adam West

EPSRC Grants: EP/F025459/1 and EP/F024886/1

Please select a section to read more about this project:

Magnetic Atom Mirror:

Schematic of the atom mirror - undulating nanowires host domain walls which
provide fringing fields which reflect incident atoms from an effective isosurface

Nanowires in a serpentine shape can be switched
between two micromagnetic configurations

As a first demonstration of the interaction of ultracold atoms with a spintronics-based device, we have realised an atom mirror based on magnetic nanowires.

To emulate an ideal magnetic mirror, we have fabricated nanowires in a characteristic undulating shape. This permits the creation of a 2D array domain walls of alternating parity.

The micromagnetic configuration of the wires can be changed via the application of external magnetic fields.

With domain walls present, the associated fringing fields interact with paramagnetic atoms via the Stern-Gerlach force. Atoms in a weak-field-seeking state are then repelled from the surface of the chip.

We approximate the interaction with the field as a point one, which allows us to define an effective isosurface from which the atoms are considered to reflect specularly. This isosurface is pictured right (yellow) and has a distinctly corrugated shape. This roughness in the isosurface leads to an overall diffuse reflection of the atomic cloud (below).

Fluorescence images of a cloud of 87Rb atoms reflecting from our nanowire array

Schematic of the experimental setup, LS = light sheet, OP = optical pumping

Example of the Monte Carlo simulation of our experiment

In order to gain a quantitative measure of the atom dynamics we use a light sheet, which passes between the position of our MOT and the nanowire array (pictured above left). Atoms passing through give a characteristic absorption feature.

Comparison with data is made via the use of Monte Carlo simulations. An example of such a simulation is shown in the animation (above right). Comparison of simulation and data shows that there is good agreement for a wide range of parameters. Example data are shown below. The first peak corresponds to falling atoms, the second peak corresonds to reflected atoms. For higher temperatures the two features are less well resolved.

Through an examination of the light sheet signal we are able to use the atoms as a probe of the micromagnetic reconfiguration. Future experiments may be able to use such atom dynamics to investigate the nature of the surface interaction

Light sheet absorption signal as a function of initial cloud temperature