Dirac’s theory, which successfully married the principles of Einstein’s relativity to the quantum property of electrons known as spin, famously predicted that the electron must have an antiparticle, subsequently discovered and named the positron. More enigmatically, the Dirac theory indicates that an isolated electron moving through empty space will vibrate back and forth. But this shaking—named Zitterbewegung from the German for ‘trembling motion’—is so rapid and so tiny in amplitude that it has never been directly observed.
Jay Vaishnav and Charles Clark of the Joint Quantum Institute, a partnership of NIST and the University of Maryland, have devised an experimental arrangement in which atoms are made to precisely mimic the behavior of electrons in Dirac’s theory. The atoms will show Zitterbewegung—but with vibrations that are slow enough and large enough to be detected.
Vaishnav and Clark’s proposal begins with an atom—rubidium-87 is an example—that has a ‘tripod’ arrangement of electron energy levels, consisting of one higher energy level above three equal-energy lower levels. Suppose, say the researchers, that such atoms are placed in a region crisscrossed by lasers at specific frequencies. Two pairs of laser beams face each other, creating a pattern of standing waves, while a third laser beam is set perpendicular to the other two.
Given the proper frequencies of light, a perfectly stationary “tripod” atom at the intersection will have the energy of its upper state and one of the three lower states slightly changed. To a moving atom, however, the electromagnetic field will look a little different, and in that case the energies of the other two lower states also change slightly.
Remarkably, those two states, moving in this particular arrangement of laser light, are governed by an equation that’s exactly analogous to the Dirac equation for the two spin states of an electron moving in empty space. In particular, as the atom moves, it flips back and forth between the two states, and that flipping is accompanied by a jiggling back and forth of the atom’s position—a version of Zitterbewegung with a frequency measured in megahertz, a hundred trillion times slower than the vibration of a free electron.
Other arrangements of lasers and atoms have been used to cleanly simulate a variety of quantum systems, says Vaishnav. Examples includes recent studies of the mechanisms of quantum magnetism and high-temperature superconductivity.** What’s unusual about this new proposal, she adds, is that it offers a simulation of a fundamental elementary particle in free space and may offer access to an aspect of electron behavior that would otherwise remain beyond observational scrutiny.
Ben Stein | EurekAlert!
NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center
Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Health and Medicine
29.03.2017 | Earth Sciences
29.03.2017 | Trade Fair News