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Category: particle physics

Nanolaser on a chip could cut computer energy use in half

Researchers at DTU have developed a nanolaser that could be the key to much faster and much more energy-efficient computers, phones, and data centers. The technology offers the prospect of thousands of the new lasers being placed on a single microchip, thus opening a digital future where data is no longer transmitted using electrical signals, but using light particles, photons. The invention has been published in the journal Science Advances.

“The nanolaser opens up the possibility of creating a new generation of components that combine high performance with minimal size. This could be in information technology, for example, where ultra-small and energy-efficient lasers can reduce energy consumption in computers, or in the development of sensors for the health care sector, where the nanolaser’s extreme light concentration can deliver high-resolution images and ultrasensitive biosensors,” says DTU professor Jesper Mørk, who co-authored the paper together with, among others, Drs. Meng Xiong and Yi Yu from DTU Electro.

Driven electrolytes are agile and active at the nanoscale

Technologies for energy storage as well as biological systems such as the network of neurons in the brain depend on driven electrolytes that are traveling in an electric field due to their electrical charges. This concept has also recently been used to engineer synthetic motors and molecular sensors on the nanoscale or to explain biological processes in nanopores. In this context, the role of the background medium, which is the solvent, and the resulting hydrodynamic fluctuations play an important role. Particles in such a system are influenced by these stochastic fluctuations, which effectively control their movements.

“When we imagine the environment inside a driven electrolyte at the nanoscale, we might think of a calm viscous medium in which ions move due to the electric field and slowly diffuse around. This new study reveals that this picture is wrong: the environment resembles a turbulent sea, which is highly nontrivial given the small scale,” explains Ramin Golestanian, who is director of the Department of Living Matter Physics at MPI-DS, and author of the study published in Physical Review Letters.

The research uncovers how the movement of the ions creates large-scale fluctuating fluid currents that stir up the environment and lead to fast motion of all the particles that are immersed in the environment, even if they are not charged.

Cutting down on quantum-dot crosstalk: Precise measurements expose a new challenge

Devices that can confine individual electrons are potential building blocks for quantum information systems. But the electrons must be protected from external disturbances. RIKEN researchers have now shown how quantum information encoded into a so-called quantum dot can be negatively affected by nearby quantum dots. This has implications for developing quantum information devices based on quantum dots.

Quantum computers process information using so-called qubits: physical systems whose behavior is governed by the laws of quantum mechanics. An electron, if it can be isolated and controlled, is one example of a qubit platform with great potential.

One way of controlling an electron is to use a quantum dot. These tiny structures trap charged particles using electric fields at the tips of metal electrodes separated by just a few tens of nanometers.

A New Way to Build 2D Materials Without Harsh Chemicals Pays Off Big

MXenes are an emerging class of two-dimensional materials whose properties depend sensitively on the atoms bound to their surfaces. A new synthesis approach now allows researchers to control these surface terminations with unprecedented precision. First identified in 2011, MXenes are a fast-expan

A New Model for Particle Charging

As flour, plastic dust, and other powdery particles get blown through factory ducts, they become charged through contact with each other and with duct walls. To avoid discharges that could ignite explosions, ducts are metallic and grounded. Still, particles remain an explosive threat if they reach a silo while charged. The microphysics of contact charging is an active area of research, as is the quest to understand the phenomenon as it plays out on larger scales in dust storms, volcanic plumes, and processing plants. Now Holger Grosshans of the German National Metrology Institute in Braunschweig and his collaborators have developed a contact-charging model that can cope with particles and walls made of different materials [1]. What’s more, the model is compatible with computational approaches used to analyze large-scale turbulent flows.

The model treats particles’ acquisition of electric charge from each other and their surroundings as a stochastic process—one that involves some randomness. The resulting charge distributions depend on the amount of charge transferred per impact and other nanoscale parameters that would be tedious to measure for each system. Fortunately, Grosshans and his collaborators found that if they determined all parameters for one system in a controlled experiment, they could readily adjust the parameters to suit other systems.

To test their model, the researchers coupled it to a popular fluid-dynamics solver and simulated 300,000 polymer microparticles stirred by a turbulent flow while confined between four walls. The combination reproduced the complex charging patterns observed in lab experiments—and it did so efficiently: The charging model added less than 0.01% to the simulation’s computational cost.

A Laser Built for Nuclear Timekeeping

Researchers have designed and demonstrated an ultraviolet laser that removes a major bottleneck in the development of a nuclear clock.

Whereas ordinary atomic clocks keep time using transitions of electrons in atoms, a prospective nuclear clock would harness a transition between states of the nucleus. Compared with electronic transitions, nuclear ones are much less sensitive to environmental disturbances, which would potentially give nuclear clocks unprecedented precision and stability. Such devices could improve GPS systems and enable more sensitive probes of fundamental physics. The main hurdle has been that nuclear transitions are extremely difficult to drive controllably using existing laser technology. Now Qi Xiao at Tsinghua University in China and colleagues have proposed and realized an intense single-frequency ultraviolet laser that can achieve such driving for thorium-229 nuclei [1, 2]. Beyond timekeeping, the team’s laser platform could find uses across quantum information science, condensed-matter physics, and high-resolution spectroscopy.

For most nuclear transitions, the energy difference between the two states lies in the kilo-electron-volt to mega-electron-volt range. Consequently, such transitions are inaccessible to today’s high-precision lasers, which can deliver photons of typically a few electron volts in energy. A long-known exception is the transition between the ground state and first excited state of thorium-229 nuclei. Indirect measurements over the past 50 years have gradually pinned down that transition’s energy difference to only about 8.4 eV. As a result, this transition is being actively investigated as a candidate for developing a nuclear clock.

A familiar magnet gets stranger: Why cobalt’s topological states could matter for spintronics

The element cobalt is considered a typical ferromagnet with no further secrets. However, an international team led by HZB researcher Dr. Jaime Sánchez-Barriga has now uncovered complex topological features in its electronic structure. Spin-resolved measurements of the band structure (spin-ARPES) at BESSY II revealed entangled energy bands that cross each other along extended paths in specific crystallographic directions, even at room temperature. As a result, cobalt can be considered as a highly tunable and unexpectedly rich topological platform, opening new perspectives for exploiting magnetic topological states in future information technologies.

The findings are published in the journal Communications Materials.

Cobalt is an elementary ferromagnet, and its properties and crystal structure have long been known. However, an international team has now discovered that cobalt hosts an unexpectedly rich topological electronic structure that remains robust at room temperature, revealing a surprising new level of quantum complexity in this material.

NOvA maps neutrino oscillations over 500 miles with 10 years of data

Neutrinos are very small, neutral subatomic particles that rarely interact with ordinary matter and are thus sometimes referred to as ghost particles. There are three known types (i.e., flavors) of neutrinos, dubbed muon, electron and tau neutrinos.

Interestingly, physicists discovered that as they travel, neutrinos can change flavor, which requires that neutrinos have a small, but not zero, mass. This phenomenon, known as neutrino oscillation, has been widely investigated in recent years, as studying it could help to infer the properties of neutrinos.

The NOvA experiment, a U.S.-based particle physics research endeavor, has been collecting data with two neutrino detectors that are far apart from each other, one located at the Fermi National Laboratory (Fermilab) in Illinois and the other at a facility in Northern Minnesota. In a recent paper, published in Physical Review Letters, the researchers involved in the NOvA experiment published some of the most precise neutrino oscillation measurements to date.

Physicists challenge a 200-year-old law of thermodynamics at the atomic scale

A long-standing law of thermodynamics turns out to have a loophole at the smallest scales. Researchers have shown that quantum engines made of correlated particles can exceed the traditional efficiency limit set by Carnot nearly 200 years ago. By tapping into quantum correlations, these engines can produce extra work beyond what heat alone allows. This could reshape how scientists design future nanoscale machines.

Two physicists at the University of Stuttgart have demonstrated that the Carnot principle, a foundational rule of thermodynamics, does not fully apply at the atomic scale when particles are physically linked (so-called correlated objects). Their findings suggest that this long-standing limit on efficiency breaks down for tiny systems governed by quantum effects. The work could help accelerate progress toward extremely small and energy-efficient quantum motors. The team published its mathematical proof in the journal Science Advances.

Traditional heat engines, such as internal combustion engines and steam turbines, operate by turning thermal energy into mechanical motion, or simply converting heat into movement. Over the past several years, advances in quantum mechanics have allowed researchers to shrink heat engines to microscopic dimensions.

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