Browse Physics

Vincent Crespi, Physics 1, 15 (2008) – Published August 25, 2008

Mesoscopics Graphene

Graphene has been idealized as a two-dimensional electron system in which the electrons behave like massless fermions, but how “perfect” is it? Scientists now show they can prepare free-standing sheets of graphene that have some of the highest electron mobilities of any inorganic semiconductor.

Sébastien Balibar, Physics 1, 16 (2008) – Published August 25, 2008

Superfluidity

Experiments indicate that, as in a superfluid, mass can flow through solid helium-4 without viscous resistance. Recent calculations shed light on how this may happen thanks to defects in the crystal lattice.

Published August 25, 2008

Graphene Mesoscopics

By adsorbing and desorbing nitrogen dioxide, it is possible to add and remove charge carriers from graphene and induce a reversible metal-insulator transition.

Published August 25, 2008

Optics Quantum Information

Squeezed states can enhance the sensitivity of a detector and the storage capability of quantum memory devices. Because these features improve with an increase in system size, researchers are exploring ways to produce squeezed states in large ensembles of atoms.

Maciej Lewenstein, Physics 1, 13 (2008) – Published August 18, 2008

Atomic & Molecular Physics

A Bose-Einstein condensate (BEC) can dramatically collapse and explode when the interactions between the atoms are sufficiently strong and attractive. Now, scientists have imaged the anisotropic, clover-leaf shape of such a collapsing gas when the attractive atomic interactions are strongly dipolar.

Michael E. Peskin, Physics 1, 14 (2008) – Published August 18, 2008

Particles & Fields Astrophysics Accelerators

New arguments based on astrophysical phenomena constrain the possibility that dangerous black holes will be produced at the CERN Large Hadron Collider.

Published August 18, 2008

Nuclear Physics

The long-held belief that nuclear states of very heavy elements that carry a large angular momentum would be unstable has been shattered in recent years. Now, a new experiment that can probe the outermost nuclear orbitals in ²⁵⁰Fm studies these states and poses a challenge to theory.

Published August 18, 2008

Nanophysics Optics

The response of nanostructured metal strips to an electromagnetic field may turn out to be similar to that of atomic gases. Periodic arrays of these artificial metal “molecules” could in principle form a metamaterial that slows light pulses and is easily integrated into optical circuits.

Published August 18, 2008

Mesoscopics

Researchers find that tunneling between the two layers of a bilayer two-dimensional electron gas is proportional to their area. Although the result may seem intuitive it poses a challenge to current theory.

Stephen Godfrey, Physics 1, 11 (2008) – Published August 11, 2008

Particles & Fields

The BABAR collaboration at SLAC has observed the radiative decay of an excited state of bottomonium (the bound state of a bottom quark and its antiparticle) to its ground state ηb. Observing this long-sought ground state should enable better tests of quantum chromodynamic calculations of quark interactions and the computational approach called lattice quantum chromodynamics.

Joseph B. Natowitz, Physics 1, 12 (2008) – Published August 11, 2008

Nuclear Physics

Heavy nuclei formed by fusion reactions often decay rapidly by fissioning into two fragments. Understanding how these decays occur and over what time scale provides a means to locate the superheavy “island of stability.”

Published August 11, 2008

Interdisciplinary Physics Nonlinear Dynamics

Acoustic vortices that interact in a nonlinear medium may be one route to a new kind of robust arithmetic computation.

Published August 11, 2008

Superconductivity

The ability to tune the onset of superconductivity in a single crystal with other means than chemical doping makes the interpretation of results much cleaner. Now, scientists demonstrate pressure-induced superconductivity in undoped crystals of the pnictide CaFe₂As₂.

Published August 6, 2008

Mesoscopics

The formation of Landau levels in a magnetic field is the hallmark of a two-dimensional electron system, such as graphene. Experiments now suggest that Landau levels can also form in carbon nanotubes.

Published August 5, 2008

Quantum Mechanics

Bell showed that quantum entanglement cannot be modeled with local hidden variables alone. Now, physicists argue that only models based exclusively on nonlocal hidden variables can reproduce all possible quantum correlations.

Published August 5, 2008

Mesoscopics

Measurements show that the tunneling of electrons through a quantum dot has a complex dependence on magnetic field and the shape of the dot. These results challenge existing pictures of spin-dependent tunneling in quantum dot devices.

Michael L. Cherry, Physics 1, 9 (2008) – Published August 4, 2008

Particles & Fields Astrophysics

Forty years ago, it was predicted that there would be a sharp cutoff in the intensity of the very-high-energy cosmic rays that strike the earth’s surface. Two collaborations—the HiRes and Auger telescopes—are providing compelling evidence for this so-called “GZK effect.”

Shamit Kachru, Physics 1, 10 (2008) – Published August 4, 2008

Atomic & Molecular Physics String Theory

Results from string theory, generalizing the anti-de Sitter/conformal field theory correspondence, may offer a fresh set of mathematical tools for understanding some kinds of phase transitions that occur in cold atomic systems.

Hélène Bouchiat, Physics 1, 7 (2008) – Published July 28, 2008

Mesoscopics

A decade ago, experimentalists showed that persistent currents can flow in nonsuperconducting mesoscopic metal rings, but there was no theory that correctly explained the magnitude or direction of the unexpectedly large currents. Theorists are now proposing a simple idea that may at last explain these results.

Igor M. Sokolov, Physics 1, 8 (2008) – Published July 28, 2008

Statistical Mechanics Biological Physics

Current technology permits tracking single molecules with exquisite precision, but the results need to be interpreted with care. Long-duration measurement of the motion of a single particle yields information that is different and complementary to that obtained from an ensemble average of many particles.

Published July 28, 2008

Quantum Information Spintronics

Spin decoherence is a fundamental obstacle in quantum computation and spintronics. Scientists show they can increase the lifetime of a localized spin in a diamond lattice up to 100 times by polarizing the surrounding spins on the lattice.

Published July 28, 2008

Gravitation

A “simple” closed-form Hamiltonian for a relativistic system of n gravitating particles, which depends only on the particles’ momenta and coordinates, is developed.

Published July 28, 2008

Atomic & Molecular Physics

The atoms in highly excited vibrational states of a diatomic molecule can be quite far apart near their maximum excursion. Physicists are now using laser spectroscopy to carefully measure the long-range effective interaction between potassium atoms in these states—an essential parameter to understanding ultracold atomic collisions.

Shou-cheng Zhang, Physics 1, 6 (2008) – Published July 23, 2008

Quantum Mechanics Semiconductor Physics

Electrons in graphene can be described by the relativistic Dirac equation for massless fermions and exhibit a host of unusual properties. The surfaces of certain band insulators—called topological insulators—can be described in a similar way, leading to an exotic metallic surface on an otherwise “ordinary” insulator.

Latha Venkataraman, Physics 1, 5 (2008) – Published July 21, 2008

Nanophysics

A molecule that links two metal electrodes could function like a chemically tunable miniature electronic device, provided that electrons can move easily across the molecular junction. A group in Leiden has now made highly conducting molecular junctions with benzene.