To process and store data, computers use signals encoded using the charge carried by electrons. But electrons have another property known as spin, which can also be used to carry and process information.
Many researchers believe "spintronic" devices will revolutionise electronics, but a number of challenges need to be overcome before new devices can be built that utilise these properties.
One of the big hurdles is to create and control streams of electrons that have their spins aligned.
This is relatively straightforward to do in metallic materials called ferromagnetics that contain tiny magnetic fields which keep the spins aligned.
The trouble is, when that neatly aligned stream is injected into a semiconductor, the spins become randomised because of a mismatch between the density of electrons in the metal and in the semiconductor.
Now, Ya-Hong Xie at the University of California, Los Angeles, has a solution.
His idea is to build a set of ferromagnetic fins on top of a semiconductor transistor. The transistor is so thin that the quantum wave function of any electron travelling through it extends into the ferromagnetic material above.
That means the ferromagnet can keep the electrons' spin in check while the transistor does whatever processing is necessary. Xie says that the process could be incorporated into current fabrication methods, bringing spintronic transistors a step closer.
Read the full spintronic injector patent application.
Justin Mullins, New Scientist consultant
Archive for the ‘physics’ Category
Spintronic electron injector
Tuesday, April 1st, 2008Gaseous gyroscope
Monday, March 31st, 2008
Micro-electromechanical gyroscopes are widely used to in devices as diverse as game controllers and weapons guidance systems. They work by vibrating a tiny mass and then measuring how it is pushed around by Coriolis forces during rotation.
But they have a number of drawbacks, say Lisa Lust and Dan Youngner from the aerospace equipment company Honeywell International in Morristown, New Jersey, US. For example, the devices require highly stable electronics, which are bulky and expensive to make, and are prone to drift as the constituent materials degrade over time.
Lust and Youngner have come up with a new type of gyroscope that avoids these problems. It is essentially a cavity containing a mixture of rubidium and xenon atoms that can be controlled using two lasers.
The first laser causes the gaseous rubidium atoms to become polarised. The rubidium atoms then transfer their spin to the xenon atoms. The second laser can be used to measure the polarisation of the xenon atoms independently of the rubidium.
If the cavity is rotating, the polarisation of the xenon atoms ends up lagging behind the polarisation of the rubidium atoms and the difference gives a straightforward measure of the rate of rotation.
Lust and Youngner say the device is low powered, physically small and robust since it has no moving or vibrating parts. They suggest it could be used to help uncrewed vehicles and robots navigate. Or it could aid personal navigational when GPS is not available – for example, inside a cave or large building.
Read the full atomic gaseous gyroscope patent application.
Justin Mullins, New Scientist consultant
But they have a number of drawbacks, say Lisa Lust and Dan Youngner from the aerospace equipment company Honeywell International in Morristown, New Jersey, US. For example, the devices require highly stable electronics, which are bulky and expensive to make, and are prone to drift as the constituent materials degrade over time.
Lust and Youngner have come up with a new type of gyroscope that avoids these problems. It is essentially a cavity containing a mixture of rubidium and xenon atoms that can be controlled using two lasers.
The first laser causes the gaseous rubidium atoms to become polarised. The rubidium atoms then transfer their spin to the xenon atoms. The second laser can be used to measure the polarisation of the xenon atoms independently of the rubidium.
If the cavity is rotating, the polarisation of the xenon atoms ends up lagging behind the polarisation of the rubidium atoms and the difference gives a straightforward measure of the rate of rotation.
Lust and Youngner say the device is low powered, physically small and robust since it has no moving or vibrating parts. They suggest it could be used to help uncrewed vehicles and robots navigate. Or it could aid personal navigational when GPS is not available – for example, inside a cave or large building.
Read the full atomic gaseous gyroscope patent application.
Justin Mullins, New Scientist consultant