Do simulated particles transport energy in constant "doses", as real free particles such as the electron do?
Shortly after midnight the phone rang at his home Prof. Mordechai (Motti) Highblom, from the Department of Condensed Matter Physics at the Weizmann Institute of Science. On the line was the postdoctoral researcher, Dr. Mithali Banerjee. "It works," she said. Thus came the culminating moment in a research effort that lasted about two years, during which, according to Dr. Banerjee's testimony, "Moti worked whole nights in the laboratory, like a young doctoral student." This is how the researchers were able to prove that simulated particles (quasi-particles), which carry fractional electric charges (a fraction of the electron charge), or even particles without a charge, carry with them the same amount of heat (energy) as real particles, such as electrons and photons.
This research is based on a series of previous discoveries by Prof. Hyblum and his research partners. Initially, the scientists were able to prove - through an experiment - a surprising theoretical prediction (something that contributed to the fact that the creator of the theory later won the Nobel Prize). According to this theory, in the system of the fractional quantum Hall effect, a kind of structures (or groups) of electrons are created in the electric current that function as "virtual particles", each of which carries an electric charge smaller than the "basic" charge of a single electron: a third of the electron's charge, a fifth or one seventh of it (in fact, the "imaginary" particles function as real particles for everything). In further experiments, the scientists were able to show that in this system - of the fractional quantum Hall effect - there are also other simulated particles, whose electric charge is equal to a quarter of the charge of the electron (that is, it has an even denominator). Then, another series of experiments put in their hands the proof of the theory, which revealed that in the same system there may also exist completely different simulated particles, which do not carry an electric charge (that is, they are neutral), which carry energy - and usually move in the opposite direction to the direction of the electric current.
The most striking feature of the quantum Hall effect (and its derivative, the fractional quantum Hall effect), is its almost perfect accuracy. That is, its electrical conductivity is measured in precise doses (determined by the electron charge and Planck's constant only). The deviation from these doses sometimes reaches only one billionth. But does this feature - the appearance of electrical conductivity in regular and precise portions - also characterize the heat conduction in the system?
On the line was the postdoctoral researcher, Dr. Mithali Banerjee. "It works," she said. Thus came the culminating moment in a research effort that lasted for about two years, during which, according to Dr. Banerjee's testimony, "Moti worked whole nights in the laboratory, like a young doctoral student"
According to a theory put forward about 20 years ago, free particles, such as electrons, photons or phonons, which move without collisions, conduct (or transport) heat in the same amount and in fixed "doses". Prof. Hyblum and the members of his research group, in collaboration with the theorists Prof. Yuval Org And Prof. Adi Stern from the Weizmann Institute of Science, and Prof. Vladimir (Dima) Feldman from Brown University in the United States, wanted to test this theory, and check if the heat transported in the system by simulated fragile or neutral particles does indeed also appear in precisely measured doses; And above all, check if it does not depend at all on the electric charge of the particles that carry it.
The scientists, including faculty scientists Dr. Vladimir Umansky and Dr. Diana Mahlo, and research student Amir Rosenblatt, showed that heat is indeed transported in precise quantities, which depend only on universal quantities such as the Boltzmann constant, Planck's constant and the mathematical value "Pi". Moreover: sometimes, while the electric current moves - and also transports heat - in a certain direction, simulated particles without charge, move - and carry heat - in the opposite direction. As measured, in certain quantum states, the amount of heat carried by the latter is greater than the amount of heat carried by the electric current, therefore, "bottom line", the heat is not transported in the direction of the electric current, but in the opposite direction. This quantum phenomenon is contrary to the concept known in classical physics.
Understanding the way in which the heat is transported, and measuring the quantum heat conductivity, adds important information about the quantum state of the system, which was impossible to obtain until now with the other means available to the scientists. This result opens many possibilities for future experiments that may expand the knowledge in this field.
8 תגובות
The fact that electrical conduction and thermal conduction are essentially related to the heat conduction of charged particles does not mean that neutral particles cannot transfer heat.
Liv Davidovitz Landau. And he passed the torch to another great scientist, his student: Yevgeny Michaelovich Lifshitz. Landau Lifshitz and Pityevsky are responsible for the old but so beautiful series in physics - about 10 volumes in physics, published by Pergamon.
This series did not continue after the collapse of the Soviet Union, so it reaches quantum electrodynamics. There were days when science in Russia dictated the world direction. Communist-led Golden Age by the way. Today the West is setting the tone in condensed matter physics, and the Indians and Chinese are nipping at its heels.
The use of mesoscopic physics - of nano meter devices, to observe quantum effects, and the quantum to classical transition is admirable. In the past, Fermi fluid theory - a combination of quantum theory with a multi-particle system, was developed to describe a hydrogen superfluid that was used to cool nuclear reactors. Professor Kapitza was the leader of the project, and he saved Landau in 1938, after he dared to express any opinions against the Soviet government (song in rhymes) and he was also Jewish. Stalin was anti-Semitic. Today, Fermi fluid theory, which is generally called condensed matter physics, is a necessary tool for calculations in nanometric devices. Landau received a Nobel Prize in 1962 for developing a huge theory, which flourishes today and whose contribution is no less than general relativity and string theory. and 3 Stalin Prizes. The same Stalin who wanted to put him in the camp. In the end, Landau was involved in a serious car accident and never returned to his former abilities.
Mitali Banerjee is an Indian researcher originally from Bangalore, India who is doing a post-doctorate in Israel.
There are postdoctoral students from industry in Israel. In my opinion, it should have been sharpened a bit. It is not possible to understand from the article that it is not an Israeli Mittal Banerjee who spoke to Moti Highblom in Arab in Hebrew, but an Indian Mitali Banerjee who probably spoke to him in English. Maybe they wanted to preserve the Israeli discovery.
Professor Highbloom's biography as told in Wikipedia is admirable. When I was a graduate student at the Technion in 1998, he was already famous.
The above is my opinion only:
The quasi-particles that Lieb Davidowitz Landau first coined for Fermi fluid theory may not be exactly virtual particles in the sense that they do not exist. Although already in Lipshitz's textbook Statistical Physics Volume II, it is written that they are virtual. It is likely that there are particles there - actual charge/spin carriers. 2 electrons in a pair that create a new quasi-particle, with a new spin are also a particle. They are called a quasi-particle in the sense that it is not possible to associate an electron and call it a Yossi, and say a Yossi at a kinetic energy level m,n. The experiment demonstrates that there is a particle at such a level, except that it is quantum. And the "energy-carrying particles" are also quantum. The photons of an electromagnetic field, the phonons of lattice vibrations. Everything is there in portions: the energy, the momentum, and the heat of conduction, and the lattice vibrations in the material are also quantized. the charge-carrying particles.
Planck already proved that in order for the formula for blackbody radiation to be correct, it should be conjugated. The difference if
This is how I think they are able to see a quantum of heat, and a particle with fractional spin, because they are probably dealing with what is known as quantum structures - boxes whose quantum dimensions are measured in at least 2 axes if not three.
The people in the picture are in reverse order. Motti Highbloom on the right.
As it happens, the discovery will go mainly to the head of the team. This is what her daughter did to his student when he proved evidence for the Big Bang by calculating the rates of the elements in the universe. Maybe they will give her a position in the academy - good luck.
I have a hypothesis and it is that:
The transfer of energy by the simulated particles, here is the expression
The microscopic-quantum to the macroscopic phenomenon of electrical resistance.
Therefore, it is possible that now the experiment should be carried out to check whether the energy conduction of simulated particles also exists in superconductors, which have no electrical resistance.