resistance

At a concert, moving through a dense crowd is tough — the tighter the pack, the less you want to move. That's how active matter usually behaves: swarms of bacteria or robot flocks freeze in tight quarters. But one research group found the opposite effect.

Ordinary electric current heats up wires — anyone who has touched a phone charger knows that. But there's another kind of current: instead of electrons rushing in a crowd in one direction, they spin in sync, like figure skaters in a pairs routine. This coordinated rotation is called a spin current, and it produces almost no heat.

In a world locked in a crystal lattice and cooled nearly to absolute zero, matter knows how to hide its deepest secrets. A quantum spin liquid is a state where electron spins never freeze, even at zero temperature, remaining in an eternally flickering superposition.

Heat a nail in a fire, and it will lengthen — everyone knows that. But heat only the tip and leave the other end cold, and the nail doesn't just get longer: it bends, because hot metal expands more than cold metal. It's this very bending, but at the atomic level, that physicists have turned into electricity.

A thin crack runs through glass. At first glance, the fracture line simply reflects the material's brittleness. But if you zoom in to the atomic level, the picture gets more complex: glass starts to resist differently when the crack accelerates.

A lithium-ion battery is like a multi-story building where lithium ions live on every floor. When you charge the battery, the ions move from floor to floor, and the whole building warms up a bit. Usually, this heat dissipates evenly, like from underfloor heating. But sometimes one spot gets too hot, and then the whole building can go up in flames.

In an insulating crystal, heat usually flows from the hot end to the cold end. But when you switch on a magnetic field, part of the heat flow veers sideways, like water running down a slope that drifts to the side when the wind pushes it. This behavior is called the thermal Hall effect.

A semiconductor film just one atom thick is like a communal apartment: it houses negatively charged electrons and positively charged 'holes.' When light hits such a film, an electron and a hole can pair up into an exciton — a bound state of an electron and a hole, akin to a hydrogen atom.