Two Delft articles about spintronics in Science

 

What’s so special about the work of Dr Lieven Vandersypen’s quantum nanoscience group is that the quantum chips it developed are made of silicon. “This is a material that we are very familiar with,” explains Vandersypen, who is also affiliated to QuTech and the Kavli Institute of Nanoscience Delft. “Silicon is widely used in transistors and so can be found in all electronic devices.”

Silicon is also a very promising material for quantum technology. The researchers showed that the quantum information of an electron spin can be transported to a photon in a silicon quantum chip. This is important to connect quantum bits across the chip and allow scale-up to large numbers of qubits.

In the meantime researchers of Dr Kobus Kuipers’ nanophotonics group at the department of Quantum Nanoscience, who also worked in the field of spintronics, demonstrated a new way to convert the spin information at room temperature into a predictable light signal. They also gave an account of their results in Science yesterday.

The researchers use the ‘spin’ of electrons rather than the charge to process data. Unfortunately, the spin only lasts a very short time, making it (as yet) difficult to exploit in electronics.

The discovery brings the worlds of spintronics and nanophotonics closer together, and might lead to the development of an energy-efficient way of processing data, in data centres, for example, the researchers state in a TU Delft press release.

The research revolved around a nano-construction consisting of two components: an extremely thin silver thread, and a 2D material called tungsten disulfide. The researchers attached the silver thread to a slice of tungsten disulfide measuring just four atoms in thickness. Using circularly polarised light, they created what are known as ‘excitons’ with a specific rotational direction.

‘We developed a lock combination’

To enable the spin information to be put to use, the Delft researchers returned to an earlier discovery. They had shown that when light moves along a nanowire, it is accompanied by a rotating electromagnetic field very close to the wire: it spins clockwise on one side of the wire, and anti-clockwise on the other side. When the light moves in the opposite direction, the spin directions change too.

So a direct link is created between the spin information and the propagation direction of the light along the nanowire. “We use this phenomenon as a type of lock combination,” explains Kuipers.