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Researchers at HZB have created an innovative technique to precisely measure minuscule temperature variations as small as 100 microkelvin in the thermal Hall effect, overcoming previous limitations caused by thermal noise. By applying this technique to terbium titanate, the team showcased its effectiveness in producing consistent and dependable outcomes. This advancement in measuring the thermal Hall effect sheds light on the behavior of coherent multi-particle states in quantum materials, particularly their interactions with lattice vibrations, known as phonons.

The laws of quantum physics apply to all materials. However, in so-called quantum materials, these laws give rise to particularly unusual properties. For example, magnetic fields or changes in temperature can cause excitations, collective states, or quasiparticles that are accompanied by phase transitions to exotic states. This can be utilised in a variety of ways, provided it can be understood, managed, and controlled: For example, in future information technologies that can store or process data with minimal energy requirements.

The thermal Hall effect (THE) plays a key role in identifying exotic states in condensed matter. The effect is based on tiny transverse temperature differences that occur when a thermal current is passed through a sample and a perpendicular magnetic field is applied (see Figure 2). In particular, the quantitative measurement of the thermal Hall effect allows us to separate the exotic excitations from conventional behavior.

Learn how researchers utilized advanced transmission electron microscopy to observe krypton atoms joining together inside nano test tubes.

Nanotechnology is in full form as scientists successfully trap individual krypton atoms inside carbon nanotubes, forming a one-dimensional gas.

In 1,827, botanist Robert Brown studied pollen particles’ motion as they were suspended in water. These little grains seemed to jitter around randomly. Brown performed as variety of tests on them and realized that all small particles, not just pollen, exhibited the same motion when suspended in water. Something other than the presence of life was causing these little particles to move around. Mathematicians took note and quickly developed a theory describing this process and named it Brownian Motion in his honor.

This theory has expanded well beyond its original context and become a beautiful subfield of mathematics called Stochastic Processes. Nowhere was this influence illustrated better than in 1905 when Albert Einstein used the theory of Brownian Motion to verify the existence of atoms. The makeup of our universe’s tiniest particles was highly debated at the time, and Einstein’s work helped solidify atomic theory.

Wow, that’s quite the leap! In order to understand how we got from pollen grains to confirming atomic theory, we’re going to have to learn some background about Brownian Motion. In this article, I’ll spend some time talking about the basics. This includes some cool videos that demonstrate the patterns of Brownian Motion and the statistics going on behind the scenes. We’ll then dive into Einstein’s version which came as one of his extremely influential series of papers in 1905. There’s a lot of ground to cover, so let’s get started!

A team of scientists at the Max Planck Institute for the Science of Light led by Dr. Birgit Stiller has succeeded in cooling traveling sound waves in waveguides considerably further than has previously been possible using laser light. This achievement represents a significant move towards the ultimate goal of reaching the quantum ground state of sound in waveguides.

Unwanted noise generated by the acoustic waves at room temperature can be eliminated. This experimental approach both provides a deeper understanding of the transition from classical to quantum phenomena of sound and is relevant to quantum communication systems and future quantum technologies.

The quantum ground state of an acoustic wave of a certain frequency can be reached by completely cooling the system. In this way, the number of quantum particles, the so-called acoustic phonons, which cause disturbance to quantum measurements, can be reduced to almost zero and the gap between classical and quantum mechanics bridged.

The discovery that neutrinos have mass was groundbreaking. However, their absolute mass remains unknown. Neutrinoless double beta decay experiments aim to determine whether neutrinos are their own antiparticles and, if so, provide a means to determine the mass of the neutrino species involved.

Determining the mass through neutrinoless double beta decay experiments using ⁷⁶ Ge is only possible if scientists understand the properties of the decay of ⁷⁶ Ge into selenium-76 (⁷⁶ Se). A study published in Physical Review C provides key input for these kinds of experiments.

Germanium-based neutrinoless double beta decay (0νββ) experiments hold great promise for unraveling the mysteries surrounding neutrinos. The observation of this rare decay process not only offers the prospect of determining the nature of these enigmatic particles, but also the determination of their mass, provided the probability governing the decay is reliably known.

A team at HZB has developed a new measurement method that, for the first time, accurately detects tiny temperature differences in the range of 100 microKelvin in the thermal Hall effect. Previously, these temperature differences could not be measured quantitatively due to thermal noise.

Their study is published in Materials & Design.

Using the well-known terbium titanate as an example, the team demonstrated that the method delivers highly reliable results. The thermal Hall effect provides information about coherent multi-particle states in quantum materials based on their interaction with lattice vibrations (phonons).

Experiments with small falling particles show that their orientations oscillate—which may help explain the settling of volcanic ash and the formation of snow.

Ice crystals and volcanic ash fall through the atmosphere in a complicated way that has been hard to capture experimentally. A new lab experiment has photographed the descent of nonspherical plastic particles that were fabricated to resemble natural particles [1]. The images reveal oscillations in the particles’ orientations as they flitter downward. The results could help in modeling the formation of snow and the transparency of clouds, which is important for weather and climate models.

In order to study how micrometer-sized particles fall in the atmosphere, researchers must address the challenge of zooming in on the particles as they pass quickly in front of the camera. “The problem is that your field of view is so small that you have a very limited chance to see the particle for a long trajectory,” says Gholamhossein Bagheri from the Max Planck Institute for Dynamics and Self-Organization in Germany. Previously, researchers tried to solve this problem by performing experiments in water with easier-to-view centimeter-sized particles. The water slows the particle motion, but the ratio of particle size to fluid viscosity—which can be characterized by the dimensionless Reynolds number—remains roughly the same for larger, waterborne particles as for smaller, airborne particles. This correspondence between the two situations implies that water-based experiments can offer information about the speed and orientation of falling particles in the atmosphere.

Scientists have developed “quantum ping-pong”: Using a special lens, two atoms can be made to bounce a single photon back and forth with high precision.

Atoms can absorb and reemit light — this is an everyday phenomenon. In most cases, however, an atom emits a light particle in all possible directions — recapturing this photon is therefore quite hard.

Continue reading “Quantum Ping-Pong: The New Era of Atomic Photon Control” »

Researchers at Columbia University have successfully synthesized the first 2D heavy fermion material. They introduce the new material, a layered intermetallic crystal composed of cerium, silicon, and iodine (CeSiI), in a research article published in Nature.

Heavy fermion compounds are a class of materials with electrons that are up to 1,000 times heavier than usual. In these materials, electrons get tangled up with magnetic spins that slow them down and increase their effective mass. Such interactions are thought to play important roles in a number of enigmatic quantum phenomena, including superconductivity, the movement of electrical current with zero resistance.

Researchers have been exploring heavy fermions for decades, but in the form of bulky, 3D crystals. The new material synthesized by Ph.D. student Victoria Posey in the lab of Columbia chemist Xavier Roy will allow researchers to drop a dimension.