AuthorTopic: Physicists Have Discovered a Metal That Conducts Electricity but Not Heat  (Read 784 times)

Offline azozeo

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Not only does this change what we know about conductors, it could also be incredibly useful.

MANUEL GARCÍA AGUILAR

(TMU) — A team of researchers in the United States have defied what we have always believed to be true about the intimate relationship between electricity conduction and heat. Conductors are no longer behaving as some physical laws stated.

In school, we learn that good conductors of electricity are also good conductors of heat. Materials such as gold, silver, and copper have both abilities—heating up and conducting electricity in a fairly easy way. It’s like an implicit rule that we always have in the back of our heads, even if we may not think of ourselves as interested in physics and thermodynamics. For example, for survival purposes, we don’t touch wires that we know are conducting large amounts of electricity.

So, we can say we have a correlation of this kind: creation of energy = creation of heat. We even have laws supporting this, such as the Wiedemann-Franz Law, which in states, in short, what we just discussed—good electricity conductors are good conductors of heat. We can even make use of the Joule effect that approaches the way that some part of the energy traveling in a conductor will be lost in heat due to electrons crashing into atoms of the material.

The vanadium dioxide (VO2) provides a completely different perspective to electricity conduction and shakes the physics world by demonstrating that there is a different path, with some specific conditions, (this is how it always works, right?) to conducting energy without heat. So how does this work?

Vanadium dioxide (VO2) has the strange ability of switching from a transparent insulator to a conductive metal at the temperature of 67 degrees Celsius (152 degrees Fahrenheit).

This was completely unexpected, as explained by lead researcher Junqiao Wu:

    “It shows a drastic breakdown of a textbook law that has been known to be robust for conventional conductors. This discovery is of fundamental importance for understanding the basic electronic behavior of novel conductors.”

This “drastic breakdown,” according to Wu, may imply making a better use of some materials that in another context wouldn’t be useful anymore, such as converting wasted heat from engines and appliances back into electricity.


https://themindunleashed.com/2019/12/metal-conducts-electricity-but-not-heat.html
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Offline RE

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https://www.sciencealert.com/scientists-see-billions-and-billions-of-entangled-electrons-flowing-through-strange-metal

PHYSICS
Physicists Finally Observe a Link Between Quantum Criticality And Entanglement
DAVID NIELD
20 JAN 2020


We know that the realm of quantum physics is science operating at a mind-bogglingly small scale, thus watching quantum interactions happen is always exciting. Now, physicists have managed to observe billions upon billions of entangled electrons passing through a metal film.

The film is a mix of ytterbium, rhodium and silicon, and is what's known as a 'strange metal', one that doesn't act as expected at very low temperatures.

"With strange metals, there is an unusual connection between electrical resistance and temperature," explained physicist Silke Bühler-Paschen from Vienna University of Technology in Austria.

"In contrast to simple metals such as copper or gold, this does not seem to be due to the thermal movement of the atoms, but to quantum fluctuations at the absolute zero temperature."

These fluctuations represent a quantum criticality – that point between quantum states which are the equivalent of transition between liquids, solids and gases in classical physics; the team says this cascade of electrons is the best evidence yet of a link between quantum criticality and entanglement.

The terahertz spectrometer used to measure entanglement. (Jeff Fitlow/Rice University)

"When we think about quantum entanglement, we think about small things," says physicist Qimiao Si, from Rice University. "We don't associate it with macroscopic objects."

"But at a quantum critical point, things are so collective that we have this chance to see the effects of entanglement, even in a metallic film that contains billions of billions of quantum mechanical objects."

The experiments Bühler-Paschen, Si and colleagues ran were incredibly challenging from many levels – from the highly complex materials synthesis required to create the strange metal, to the delicate terahertz spectroscopy required to observe the electrons.

Ultimately, after a painstaking process, the team found what they were looking for: the tell-tale sign of quantum criticality known as frequency over temperature scaling.

"Conceptually, it was really a dream experiment," says Si. "Probe the charge sector at the magnetic quantum critical point to see whether it's critical, whether it has dynamical scaling."

"If you don't see anything that's collective, that's scaling, the critical point has to belong to some textbook type of description. But, if you see something singular, which in fact we did, then it is very direct and new evidence for the quantum entanglement nature of quantum criticality."

What all of this high-level physics means is a lot of potential: potential quantum advancements in computing, communications and more. Scientists have hypothesised about a link between quantum entanglement and quantum criticality before, but now it's been observed.

The study of quantum states is still in its very early stages, but it could hold the key to all kinds of weird science, like high-temperature superconductivity – which is also believed to be underpinned by quantum criticality.

Understanding how these quantum phases switch gives us a better chance of being able to control them in the future – and although that's still a long way off, it just got a little closer.

"Our findings suggest that the same underlying physics – quantum criticality – can lead to a platform for both quantum information and high-temperature superconductivity," says Si. "When one contemplates that possibility, one cannot help but marvel at the wonder of nature."

The research has been published in Science.
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Offline Eddie

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https://www.sciencealert.com/scientists-see-billions-and-billions-of-entangled-electrons-flowing-through-strange-metal

PHYSICS
Physicists Finally Observe a Link Between Quantum Criticality And Entanglement
DAVID NIELD
20 JAN 2020


We know that the realm of quantum physics is science operating at a mind-bogglingly small scale, thus watching quantum interactions happen is always exciting. Now, physicists have managed to observe billions upon billions of entangled electrons passing through a metal film.

The film is a mix of ytterbium, rhodium and silicon, and is what's known as a 'strange metal', one that doesn't act as expected at very low temperatures.

"With strange metals, there is an unusual connection between electrical resistance and temperature," explained physicist Silke Bühler-Paschen from Vienna University of Technology in Austria.

"In contrast to simple metals such as copper or gold, this does not seem to be due to the thermal movement of the atoms, but to quantum fluctuations at the absolute zero temperature."

These fluctuations represent a quantum criticality – that point between quantum states which are the equivalent of transition between liquids, solids and gases in classical physics; the team says this cascade of electrons is the best evidence yet of a link between quantum criticality and entanglement.

The terahertz spectrometer used to measure entanglement. (Jeff Fitlow/Rice University)

"When we think about quantum entanglement, we think about small things," says physicist Qimiao Si, from Rice University. "We don't associate it with macroscopic objects."

"But at a quantum critical point, things are so collective that we have this chance to see the effects of entanglement, even in a metallic film that contains billions of billions of quantum mechanical objects."

The experiments Bühler-Paschen, Si and colleagues ran were incredibly challenging from many levels – from the highly complex materials synthesis required to create the strange metal, to the delicate terahertz spectroscopy required to observe the electrons.

Ultimately, after a painstaking process, the team found what they were looking for: the tell-tale sign of quantum criticality known as frequency over temperature scaling.

"Conceptually, it was really a dream experiment," says Si. "Probe the charge sector at the magnetic quantum critical point to see whether it's critical, whether it has dynamical scaling."

"If you don't see anything that's collective, that's scaling, the critical point has to belong to some textbook type of description. But, if you see something singular, which in fact we did, then it is very direct and new evidence for the quantum entanglement nature of quantum criticality."

What all of this high-level physics means is a lot of potential: potential quantum advancements in computing, communications and more. Scientists have hypothesised about a link between quantum entanglement and quantum criticality before, but now it's been observed.

The study of quantum states is still in its very early stages, but it could hold the key to all kinds of weird science, like high-temperature superconductivity – which is also believed to be underpinned by quantum criticality.

Understanding how these quantum phases switch gives us a better chance of being able to control them in the future – and although that's still a long way off, it just got a little closer.

"Our findings suggest that the same underlying physics – quantum criticality – can lead to a platform for both quantum information and high-temperature superconductivity," says Si. "When one contemplates that possibility, one cannot help but marvel at the wonder of nature."

The research has been published in Science.

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