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It’s not often that messing around in the lab has produced a fundamental breakthrough, à la Michael Faraday with his magnets and prisms. Even more uncommon is the discovery of the same thing by two research teams at the same time: Newton and Leibniz come to mind. But every so often, even the rarest of events does happen. The summer of 2021 has been a banner season for condensed-matter physics. Three separate teams of researchers have created a crystal made entirely of electrons — and one of them actually did it by accident.

The researchers were working with single-atom-thick semiconductors, cooled to ultra-low temperatures. One team, led by Hongkun Park along with Eugene Demler, both of Harvard, discovered that when very specific numbers of electrons were present in the layers of these slivers of semiconductor, the electrons stopped in their tracks and stood “mysteriously still.” Eventually colleagues recalled an old idea having to do with Wigner crystals, which were one of those things that exist on paper and in theory but had never been verified in life. Wigner had calculated that because of mutual electrostatic repulsion, electrons in a monolayer would assume a tri-grid pattern.

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“While there have been published doubts raised about the accuracy of some of this CMB data, taken at face value it appears we may not have the right understanding, and it changes how big the Hubble constant should be today,” Riess said at the time.

“This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95% of everything and don’t emit light, such as dark energy, dark matter and dark radiation.” Given its breadth and scope, astronomers around the world have taken the findings of Riess and his colleagues very seriously. After all, in 2011 Riess had shared the Nobel Prize in Physics for the initial discovery that the universe wasn’t just expanding, but that the rate at which it was doing so was also increasing.

Erik Verlinde of the University of Amsterdam has spent much of his time since 2010 attempting to develop a totally new theory of gravity, one that explains such observations without the need to invoke the likes of dark matter and dark energy. This resulted in his theory of emergent gravity, so-called because gravity is not a fundamental force after all, but an emergent phenomenon, similar to temperature emerging from the movement of particles.

BepiColombo will fly by the planet’s night side, so images during the closest approach wouldn’t be able to show much detail.

The mission team anticipates the images will show large impact craters that are scattered across Mercury’s surface, much like our moon. The researchers can use the images to map Mercury’s surface and learn more about the planet’s composition.

Some of the instruments on both orbiters will be turned on during the flyby so they can get a first whiff of Mercury’s magnetic field, plasma and particles.

Unplanned discovery could lead to future pivotal discoveries in batteries, fuel cells, devices for converting heat to electricity and more.

Scientists normally conduct their research by carefully selecting a research problem, devising an appropriate plan to solve it and executing that plan. But unplanned discoveries can happen along the way.

Mercouri Kanatzidis, professor at Northwestern University with a joint appointment in the U.S. Department of Energy’s (DOE) Argonne National Laboratory, was searching for a new superconductor with unconventional behavior when he made an unexpected discovery. It was a material that is only four atoms thick and allows for studying the motion of charged particles in only two dimensions. Such studies could spur the invention of new materials for a variety of energy conversion devices.

Researchers have discovered a complex landscape of electronic states that can co-exist on a kagome lattice, resembling those in high-temperature superconductors, a team of Boston College physicists reports in an advance electronic publication of the journal Nature.

The focus of the study was a bulk single crystal of a topological kagome metal, known as CsV₃Sb₅—a metal that becomes superconducting below 2.5 degrees Kelvin, or minus 455 degrees Fahrenheit. The exotic material is built from atomic planes composed of Vanadium atoms arranged on a so-called kagome lattice—described as a pattern of interlaced triangles and hexagons—stacked on top of one another, with Cesium and Antimony spacer layers between the kagome planes.

The material offers a window into how the physical properties of quantum solids—such as light transmission, electrical conduction, or response to a magnetic field —relate to the underlying geometry of the atomic lattice structure. Because its geometry causes destructive interference and “frustrates” the kinetic motion of traversing electrons, kagome lattice materials are prized for offering the unique and fertile ground for the study of quantum electronic states described as frustrated, correlated and topological.

Reversible system can flip the magnetic orientation of particles with a small voltage; could lead to faster data storage and smaller sensors.

Most of the magnets we encounter daily are made of “ferromagnetic” materials. The north-south magnetic axes of most atoms in these materials are lined up in the same direction, so their collective force is strong enough to produce significant attraction. These materials form the basis for most of the data storage devices in today’s high-tech world.

Less common are magnets based on ferrimagnetic materials, with an “i.” In these, some of the atoms are aligned in one direction, but others are aligned in precisely the opposite way. As a result, the overall magnetic field they produce depends on the balance between the two types — if there are more atoms pointed one way than the other, that difference produces a net magnetic field in that direction.

In her March 7 public lecture at Perimeter Institute, Emily Levesque discusses the history of stellar astronomy, present-day observing techniques and exciting new discoveries, and explores some of the most puzzling and bizarre objects being studied by astronomers today.

Perimeter Institute (charitable registration number 88,981 4323 RR0001) is the world’s largest independent research hub devoted to theoretical physics, created to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. The Perimeter Institute Public Lecture Series is made possible in part by the support of donors like you. Be part of the equation: https://perimeterinstitute.ca/inspiring-and-educating-public.

Continue reading “Emily Levesque Public Lecture: The Weirdest Stars in the Universe” »

Last year, physicists reported that an experimental dark matter detector picked up a strange signal that could hint at new physics, with several suspects highlighted. Now, Cambridge scientists have proposed an answer that wasn’t considered at the time – the experiment may have picked up the first direct detection of dark energy, the mysterious force that’s accelerating the expansion of the universe.

Although it’s thought to outnumber regular matter five to one, dark matter remains elusive. It doesn’t interact with light and seems to mostly make itself known through gravitational influence on cosmic scales, like stars, galaxies and galaxy clusters. But once in a while, a dark matter particle might bump into a regular matter particle in a way that we could detect, with the right equipment.

XENON1T was one version of that equipment. Running in Italy between 2016 and 2,018 the experiment was essentially a big tank full of liquid xenon, kept deep underground. The idea was that if a dark matter particle zipped through the tank, it would excite the xenon atoms to produce a flash of light and free electrons, which a suite of sensors can detect.

Today, the LHCb experiment at CERN is presenting a new discovery at the European Physical Society Conference on High Energy Physics (EPS-HEP). The new particle discovered by LHCb, labelled as Tcc+, is a tetraquark – an exotic hadron containing two quarks and two antiquarks. It is the longest-lived exotic matter particle ever discovered, and the first to contain two heavy quarks and two light antiquarks.

A tetraquark composed of two charm quarks and an up and a down antiquark (Image: D. Dominguez/CERN)

Quarks are the fundamental building blocks from which matter is constructed. They combine to form hadrons, namely baryons, such as the proton and the neutron, which consist of three quarks, and mesons, which are formed as quark-antiquark pairs. In recent years a number of so-called exotic hadrons – particles with four or five quarks, instead of the conventional two or three — have been found. Today’s discovery is of a particularly unique exotic hadron, an exotic exotic hadron if you like.