Scientists at Georgia Tech have discovered a new quantum state in a quirky material. In a phenomenon never before seen in anything else, the team found that applying a magnetic field increased the material’s electrical conductivity by a billion percent.
Some materials are known to change their conductivity in response to a changing magnetic field, a property called magnetoresistance. But in the new study, the material does so to an incredible degree, exhibiting colossal magnetoresistance.
The material is an alloy of manganese, silicon and tellurium, which takes the form of octagonal cells arranged in a honeycomb pattern, and stacked in sheets. Electrons move around the outside of those octagons, but when there’s no magnetic field applied they travel in random directions, causing a traffic jam. That effectively makes the material act like an insulator.
But when the magnetic field is applied, the electrons begin moving in a set direction, allowing them to flow quickly and generate an electrical current. That makes it a very effective conductor – in fact, it’s a seven magnitude increase in conductivity. To put it another way, that’s a boost of one billion percent.
Most intriguingly, this switch only works if the magnetic field is applied perpendicular to the surface of the material. In all other known materials that show magnetoresistance, the angle of the magnetic field doesn’t make a difference to the strength of the effect.
“The phenomenon defies all existing theoretical models and experimental precedents,” said Itamar Kimchi, an author of the study.
In other experiments, the team found that the switch can also be triggered by applying an electrical current. This happens slower, taking a few seconds or minutes to make the transition.
The team says that this second version could be more immediately applicable to quantum devices, such as computers, sensors and communication systems. But before then, more research will need to be conducted to better understand this new quantum state, and investigate other materials that might work in the same way.
The research was published in the journal Nature.
Source: Georgia Tech
