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A new discovery led by Princeton University could upend our understanding of how electrons behave under extreme conditions in quantum materials. The finding provides experimental evidence that this familiar building block of matter behaves as if it is made of two particles: one particle that gives the electron its negative charge and another that supplies its magnet-like property, known as spin.

“We think this is the first hard evidence of spin-charge separation,” said Nai Phuan Ong, Princeton’s Eugene Higgins Professor of Physics and senior author on the paper published this week in the journal Nature Physics.

The experimental results fulfill a prediction made decades ago to explain one of the most mind-bending states of matter, the quantum spin liquid. In all materials, the spin of an electron can point either up or down. In the familiar magnet, all of the spins uniformly point in one direction throughout the sample when the temperature drops below a critical temperature.

Physicists have measured the “skin” of an atom for the first time and, perhaps unsurprisingly, it is extremely thin. The measurement may help us understand the properties of neutron stars.

Lead-208, an isotope that contains 82 protons and 126 neutrons, has a type of nucleus that physicists refer to as “doubly magic” because both the protons and the neutrons are arranged neatly into shells inside the nucleus. These shells keep the atom relatively stable and make it simpler to experiment on, so when the PREX collaboration at the Thomas Jefferson National Accelerator Facility in Virginia set out to measure neutron skin, they opted to experiment on lead-208.

An international research team led by the University of Cologne has succeeded for the first time in connecting several atomically precise nanoribbons made of graphene, a modification of carbon, to form complex structures. The scientists have synthesized and spectroscopically characterized nanoribbon heterojunctions. They then were able to integrate the heterojunctions into an electronic component. In this way, they have created a novel sensor that is highly sensitive to atoms and molecules. The results of their research have been published under the title Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions’ in Nature Communications. The work was carried out in close cooperation between the Institute for Experimental Physics with the Department of Chemistry at the University of Cologne, as well as with research groups from Montreal, Novosibirsk, Hiroshima, and Berkeley. It was funded by the German Research Foundation (DFG) and the European Research Council (ERC).

The heterojunctions of graphene nanoribbons are just one nanometer—one millionth of a millimeter—wide. Graphene consists of only a single layer of carbon atoms and is considered the thinnest material in the world. In 2010, researchers in Manchester succeeded in making single-atom layers of graphene for the first time, for which they won the Nobel Prize. The graphene nanoribbon heterojunctions used to make the sensor are each seven and fourteen carbon atoms wide and about 50 nanometres long. What makes them special is that their edges are free of defects. This is why they are called atomically precise nanoribbons, explained Dr. Boris Senkovskiy from the Institute for Experimental Physics. The researchers connected several of these nanoribbon heterojunctions at their short ends, thus creating more complex heterostructures that act as tunneling barriers.

The heterostructures were investigated using angle-resolved photoemission, optical spectroscopy, and scanning tunneling microscopy. In the next step, the generated heterostructures were integrated into an electronic device. The electric current flowing through the nanoribbon heterostructure is governed by the quantum mechanical tunneling effect. This means that under certain conditions, electrons can overcome existing energy barriers in atoms by ‘tunneling,’ so that a current then flows even though the barrier is greater than the available energy of the electron.

An international team of physicists has shown experimentally for the first time how a Bose-Einstein condensate — tens of thousands of quanta of ‘liquid light’ — is formed in the thinnest monatomic film of a semiconductor crystal. The team includes the head of the Spin Optics Laboratory at St Petersburg University, Professor Alexey Kavokin. This discovery will help create new types of lasers capable of producing qubits — the main integral parts of quantum computers of the future.

The results of a new muon experiment are stirring up particle physics.

The results of a Fermilab experiment might open up the standard model of particle physics.

New observations and simulations show that jets of high-energy particles emitted from the central massive black hole in the brightest galaxy in galaxy clusters can be used to map the structure of invisible inter-cluster magnetic fields. These findings provide astronomers with a new tool for investigating previously unexplored aspects of clusters of galaxies.

As clusters of galaxies grow through collisions with surrounding matter, they create bow shocks and wakes in their dilute plasma. The plasma motion induced by these activities can drape intra-cluster magnetic layers, forming virtual walls of magnetic force. These magnetic layers, however, can only be observed indirectly when something interacts with them. Because it is simply difficult to identify such interactions, the nature of intra-cluster magnetic fields remains poorly understood. A new approach to map/characterize magnetic layers is highly desired.

In 1884, Edwin Abbott wrote the novel Flatland: A Romance in Many Dimensions as a satire of Victorian hierarchy. He imagined a world that existed only in two dimensions, where the beings are 2D geometric figures. The physics of such a world is somewhat akin to that of modern 2D materials, such as graphene and transition metal dichalcogenides, which include tungsten disulfide (WS₂), tungsten diselenide (WSe₂), molybdenum disulfide (MoS₂) and molybdenum diselenide (MoSe₂).

Modern 2D materials consist of single-atom layers, where electrons can move in two dimensions but their motion in the third dimension is restricted. Due to this ‘squeeze’, 2D materials have enhanced optical and electronic properties that show great promise as next-generation, ultrathin devices in the fields of energy, communications, imaging and quantum computing, among others.

Typically, for all these applications, the 2D materials are envisioned in flat-lying arrangements. Unfortunately, however, the strength of these materials is also their greatest weakness—they are extremely thin. This means that when they are illuminated, light can interact with them only over a tiny thickness, which limits their usefulness. To overcome this shortcoming, researchers are starting to look for new ways to fold the 2D materials into complex 3D shapes.

In 2001 at the Brookhaven National Laboratory in Upton, New York, a facility used for research in nuclear and high-energy physics, scientists experimenting with a subatomic particle called a muon encountered something unexpected.

To explain the fundamental physical forces at work in the universe and to predict the results of high-energy particle experiments like those conducted at Brookhaven, Fermilab in Illinois, and at CERN ’s Large Hadron Collider in Geneva, Switzerland, physicists rely on the decades-old theory called the Standard Model, which should explain the precise behavior of muons when they are fired through an intense magnetic field created in a superconducting magnetic storage ring. When the muon in the Brookhaven experiment reacted in a way that differed from their predictions, researchers realized they were on the brink of a discovery that could change science’s understanding of how the universe works.

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John Martinis has done groundbreaking research on coherent superconducting devices since his PhD at the University of California, Berkeley, in 1985. These superconducting devices can be modeled as lumped-element electric circuits using Josephson junctions, capacitors and inductors as components. The fact that a superconducting phase across a Josephson junction can display coherent quantum behavior – even though it is a property of the wave function of an immense number of electrons – can be viewed as a fundamental discovery [1], kickstarting, in retrospect, the field of superconducting quantum computing.

John Martinis invented and developed the superconducting phase qubit, based on a current-biased Josephson junction, for the purpose of scalable multi-qubit quantum computing [2]. In 2002, he first demonstrated coherent Rabi oscillations and quantum measurement for such superconducting phase qubit [3]. He has had a longstanding interest in understanding the origin of noise in superconducting electric circuits as these sources of noise naturally limit qubit coherence. In particular, his understanding of noise sources such as dielectric loss, flux noise and the presence and dynamics of quasi-particles [4], by means of simple physical models, have been instrumental in the field. The effect and mitigation of quasi-particles and how they are affected by radiation and cosmic rays continues to be of high interest for the future of superconducting quantum devices [5, 6].

An important step showing his leadership and commitment to building a quantum computer came with his 2014 move, as a Professor at UCSB, to Google, where he gathered a large team of physicists and engineers to tackle the challenge of making a multi-qubit programmable processor. This team has excelled in its relentless focus on optimizing device performance by implementing successful engineering choices for qubit design, couplers and scalable I/O.