System Bits: Jan. 6

ETH researchers have measured a stepwise change in conductivity as the atoms pass through tiny structures, which is the first time this quantum effect has been observed for electrically neutral particles; Yale University researchers have discovered some key features of liquid droplets that could provide additional optical or electrical functionality, without sacrificing mechanical performance.

popularity

Quantum channel of light
In experiments using ultracold atoms and laser light, ETH researchers have measured a stepwise change in conductivity as the atoms pass through tiny structures. This is the first time that this quantum effect has been observed for electrically neutral particles.

A point contact through which neutral, ultracold atoms flow. According to the laws of quantum physics, conductivity can only change in discrete steps. (Source: ETH)

A point contact through which neutral, ultracold atoms flow. According to the laws of quantum physics, conductivity can only change in discrete steps. (Source: ETH)

Two vessels filled with gas and connected by a channel – this is the basic setting for the experiments carried out by the physicists at the ETH Institute for Quantum Electronics. As one vessel contains more gas than the other, particles flow through the channel from one side to the other.

The researchers were seeking to answer the question of how the conductivity changes as the channel is gradually made narrower.

Initially, the conductivity decreases smoothly, but at some point an amazing phenomenon appears: the conductivity does not change continuously anymore, but in steps, and the size of the steps is determined by a fundamental entity known as the Planck constant, which is an immediate consequence of quantum physics.

The phenomenon has been observed before, but only in electronic systems, such as in quantum point contacts in specific semiconductor structures. Now these have been observed for the first time quantization of conductivity in neutral matter.

Liquid drops make solids stiffer
Engineers at Yale University have discovered that while large drops of liquids are softer than the solid that surrounds them, extremely tiny drops of liquid can actually be stiffer than certain solids, and when they’re ‘just right,’ the liquid drops have the exact same stiffness as the surrounding solid.

The key to this is the fact that liquid has a tendency to have as small a surface as possible — a contractile force known as “surface tension” which, allows a cup of water to be filled slightly above the brim without spilling, for example.

When the embedded liquid droplets are very small, surface tension makes them so stiff that they can actually make a solid stronger.”

It turns out that the importance of surface tension is inversely proportional to the size, so what’s just a negligible force for big things becomes a strong force for very small things — which in turn can strongly affect the material as a whole.

The researchers believe these results provide engineers with “a new knob to turn” to control the properties of composite materials.

Yale engineers are strengthening soft materials with surface tension. (Source: Yale University)

Yale engineers are strengthening soft materials with surface tension.
(Source: Yale University)



  • Amazed

    I wonder if this plays a factor in bone structure strength.