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Category: particle physics – Page 14

Sprinkling nanoparticles on spintronics

Today, I want to walk you through a deceptively simple innovation from the lab at Loughborough University (PI: Prof Marco Peccianti): what happens when we decorate a spintronic heterostructure with a sparse layer of plasmonic nanoparticles? This isn’t just a lab curiosity—it’s a step toward making terahertz sources more efficient, compact, and practical for real-world applications like high-speed communications, noninvasive imaging, and advanced spectroscopy.

Spintronic terahertz emitters rely on a thin, multilayer stack—typically heavy metal like tungsten (W), a ferromagnetic layer such as iron (Fe), and a platinum (Pt) cap. A femtosecond laser pulse strikes the structure, rapidly heating electrons and generating a pure spin current through spin-orbit torque effects.

This spin current converts into broadband terahertz radiation at the interfaces, bypassing the need for cumbersome phase-matching crystals used in traditional optical rectification. It’s elegant and scalable, but most laser light reflects off or transmits through without effectively coupling to the magnetic layer, limiting spin injection and THz output power.

Water simulation of famous quantum effect reveals unexpected wave patterns

In the quirky quantum world, particles can be affected by forces that they never directly encounter. A classic example is the Aharonov–Bohm (AB) effect, where electrons are affected by a magnetic field, despite not passing through it. Although predicted in 1959, it took more than two decades to confirm this effect experimentally, as the specific changes to the electrons’ wave properties could only be inferred indirectly, and with great difficulty. Now, physicists from the Okinawa Institute of Science and Technology (OIST), in collaboration with the University of Oslo and Universidad Adolfo Ibáñez, have used a classical fluid analog that mimics and extends the AB effect using a simple platform: a water tank.

In work published in Communications Physics, researchers have revealed that when water waves are sent towards a swirling vortex from opposite directions, it causes a striking pattern, with one or more lines of momentarily still water radiating outward and rotating in an almost hypnotic way.

“This was something new and unexpected,” says Aditya Singh, a Ph.D. student in the Nonlinear and Non-equilibrium Physics Unit and co-first author of the study. “That’s what makes this fluid analog system so valuable. It reveals topological effects—wave behaviors that occur across the whole system—that can’t be seen in quantum experiments.”

A hidden property of light could power future nanomachines

Light does more than illuminate the world—it can also push and twist matter. It was back in the 1870s that James Clerk Maxwell first predicted that light carries momentum and can exert pressure on objects. Nearly a century later, in the 1970s, Arthur Ashkin asked why not use this property of light to hold and push around tiny particles. He developed optical tweezers that use focused laser beams to trap and move nanoscale objects.

While scientists have long known that light can exert small forces, detecting them has been extremely difficult. Objects at this scale are constantly jostled by random thermal motion, making the subtle influence of light hard to measure.

There’s a range of magic angles to study superconductivity in a twisted 2D semiconductor

Last year, tungsten diselenide (WSe2) had its magic moment. Two independent research groups discovered “magic angles” at which two atom-thin layers of the unique semiconductor, when twisted relative to one another into what’s known as a moire pattern, can superconduct electricity. Cory Dean and his colleagues at Columbia documented superconductivity at a 5° twist angle; upstate at Cornell, Jie Shan and Kin Fai Mak’s team saw it at around 3.5°. Until then, graphene was the only other moire material capable of the feat.

Writing again in Nature on April 1, Dean and his colleagues fill in what happens between their observed magic angle and Cornell’s. Though the initial results struck researchers as two potentially distinct types of superconductivity, they are in fact smoothly connected. “Graphene has a magic angle of 1.1°. WSe2 has a magic continuum,” said Columbia physics graduate student Yinjie Guo, lead author of both Columbia Nature papers.

That wide continuum of superconducting twist angles makes WSe2 a more robust platform to explore the phenomenon than graphene, which cannot deviate by more than a tenth of a degree from its magic angle. “That’s a very specific condition you have to get to, and it’s been a real bottleneck,” noted Dean. “Working with WSe2 is extremely reproducible, which makes it much more possible to build new theories about superconductivity.”

Generalized optical meta-spanners empower arbitrary light paths for multitasking optical manipulation

Have you ever wished to drive microscopic matter along an arbitrarily tailored trajectory instead of just a circle? That’s exactly what we set out to achieve.

The field of photonic force manipulation has opened new avenues for controlling the microscopic world with light. Since the invention of optical tweezers in 1986, the non-contact trapping and manipulation of microscopic particles using the momentum and angular momentum of light has become an indispensable tool in biophysics, soft matter science, and micro-nanotechnology—a contribution recognized by the 2018 Nobel Prize in Physics.

Conventional optical tweezers rely on the intensity gradient of a Gaussian beam to generate a three-dimensional restoring potential for stable particle trapping.

What makes Mars’ magnetotail flap? Two spacecraft point to magnetic reconnection

The sun continuously blasts charged, magnetic field-carrying particles, or plasma, in all directions. This solar wind interacts with the magnetic fields and atmospheres of several of our solar system’s planets and other bodies, sculpting long magnetic tails of charged particles—magnetotails—that stretch into space behind them.

Magnetotails contain thin layers of electric current-carrying plasma sheets, which sometimes “flap” in an up-and-down waving motion. Spacecraft observations have revealed that flapping in Earth’s magnetotail can be driven by a process called magnetic reconnection, in which magnetic field lines rapidly break and then snap together in a new configuration, releasing stored energy. However, whether reconnection plays this same role beyond Earth has thus far been a mystery.

Yuanzheng Wen and colleagues report the first evidence that magnetic reconnection may also trigger magnetotail flapping at Mars. Their findings are published in the journal AGU Advances.

Feynman: The Past and Future Are the Same Thing

The past and future are the same thing | feynman on time symmetry.

Discover one of physics’ most mind-bending secrets: the fundamental laws of nature don’t know which way time flows! In this exploration of Feynman’s ideas on time symmetry, we dive deep into how the equations of physics work equally well forwards and backwards, why positrons are electrons moving backward through time, and how the Wheeler-Feynman absorber theory suggests the future might influence the past.

From billiard balls to quantum mechanics, from Maxwell’s equations to the mystery of why we remember yesterday but not tomorrow, this video unravels the beautiful symmetry hidden beneath our everyday experience of time.

Topics Covered:
• Time symmetry in fundamental physics
• Positrons as electrons traveling backward in time
• Wheeler-Feynman absorber theory
• The thermodynamic arrow of time
• Path integral formulation and quantum mechanics
• Why time appears to flow in one direction
• CP violation and the weak nuclear force.

Perfect for physics enthusiasts, students, and anyone curious about the nature of time and reality.

⚠️ DISCLAIMER: This is AI-generated content created in the style of Richard Feynman’s teaching approach. The script synthesizes information from various sources about Feynman’s work and ideas in theoretical physics, including his lectures, published papers, and documented contributions to quantum electrodynamics and time-symmetric theories. While based on authentic concepts from Feynman’s career, this is an educational interpretation and not actual recorded material from Richard Feynman.

Continue reading “Feynman: The Past and Future Are the Same Thing” | >

Where Does Mass Come From? Scientists Find Evidence of a New Exotic Nuclear State

New experiments reveal possible η′-mesic nuclei, offering evidence that particle masses shift inside nuclear matter and shedding light on how mass originates from vacuum structure. Almost everything around us has mass, but its origin is still a fundamental question in physics. Current theory sugg

Inside a White Dwarf, Matter Stops Behaving Normally

What happens when gravity crushes a dead star so completely that atoms themselves are destroyed? Inside a white dwarf, matter enters a state so extreme that the normal rules of physics no longer apply. The familiar categories — solid, liquid, gas — all break down. What holds the star up is not heat, not fusion, not any force you encounter in everyday life. It is a quantum mechanical rule about electrons that most people have never heard of: the Pauli exclusion principle.

In this calming long-form science documentary, we explore what white dwarfs really are, why their matter is millions of times denser than anything on Earth, and how a law governing subatomic particles can hold up an object with the mass of the sun. We break down electron degeneracy pressure in physically intuitive terms, explain why these stellar remnants can cool for trillions of years without ever collapsing, and reveal the Chandrasekhar limit — the critical mass threshold beyond which even quantum mechanics loses its battle against gravity, leading to some of the most violent explosions in the universe.

From the death of sun-like stars to the far future of the cosmos, this is the story of matter pushed to its absolute limit.

Sources and Further Reading:

Chandrasekhar, S. (1931). \

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