Experimental atomic physicists have discovered there is a maximum amount of electrical resistance, or resistivity, that can result from collisions between electrons.

A team from the University of Toronto, L’École Normale Supérieure in Paris, and Lehigh University in Pennsylvania studied ultracold potassium atoms cooled to near absolute zero. They found that when increasing the rate at which atoms collide, the resulting resistance eventually stops increasing, offering new insights into what causes resistivity at the microscopic level.

“Electron-on-electron collisions are known to increase resistivity in some pure materials,” explains Professor Joseph Thywissen in the Department of Physics and the Centre for Quantum Information and Quantum Control in the Faculty of Arts & Science at the University of Toronto, senior author of a study published in Physical Review Letters. “The energy produced by electrical resistance shows up as heat. Transmission lines, for instance, lose up to 8% of generated electrical power. Resistivity is also interesting to study because it can be a signature of new physics in materials.”

Many quantum effects can be observed only when a small number of particles is studied—individual atoms, molecules or photons, for example, carefully shielded from the rest of the world. But what about macroscopic objects, consisting of an unimaginably large number of particles? Can they, too, display effects that provide a direct glimpse into the quantum world?

Experimentalists at TU Wien have now shown that this is possible: A centimeter-sized crystal of a so-called strange metal was investigated, and a high degree of quantum entanglement was detected. This was made possible by a clearly defined method from quantum information theory: the quantum Fisher information.

It establishes a new bridge between solid-state physics and quantum physics: Quantum entanglement can be directly quantified in a macroscopic strange-metal material. The paper is published in the journal Nature Physics.

A new experiment probes the quantum geometry of electronic wave functions involved in a nonlinear Hall response.

The transport properties of quantum materials often vary periodically with the strength of an applied magnetic field. These quantum oscillations have long provided physicists with an indispensable tool for extracting subtle, otherwise-inaccessible information on electronic phases of matter [1]. Now an experiment by Jinrui Zhong of the Beijing Institute of Technology and his colleagues has revealed a novel kind of quantum oscillation in moiré systems [2]. These are materials made from stacked monolayers that are twisted with respect to each other to create, in effect, atomic lattices with much wider unit cells. The experiment pointed to a special mechanism for facilitating the novel periodic fluctuations: the emergence of so-called Brown-Zak fermions.

The ability to control the movement of negatively charged particles (i.e., electrons) is central to the functioning of all modern electronic devices. This control is typically attained using a gate, an electrode via which an applied electric field alters a material’s electrical properties.

In many electronic devices, the effectiveness of electrical gating depends on a device’s capacitance (i.e., a measure of how much electric charge can be induced or stored for a given voltage). Recently, however, electronics engineers have been exploring the potential of new materials that exhibit unusual collective electron behaviors, which could be leveraged to surpass the gating performance of contemporary electronics.

Researchers at University of California, Los Angeles (UCLA) and University of California, Riverside (UCR) recently demonstrated the potential of a new quasi-one-dimensional (1D) quantum material, showing that it can dramatically enhance the electrical control of collective electronic states known as charge density waves (CDWs).

An experiment with a toy universe made up of extremely cold atoms shows how time can emerge from quantum interactions, instead of existing by default