Volume 10 Issue 5, May 2014

It is commonly believed that solids with spatial inversion symmetry do not display spin–orbit effects. However, first-principles calculations now reveal unexpected spin structure for centrosymmetric crystals.

Holographic dualities discovered in string theory may provide methods for extracting the real-time response of quantum systems from numerical simulations performed in imaginary time.

An unusual form of symmetry breaking in coupled microresonators with balanced optical gain and loss is now exploited to realize a novel type of optical isolator.

Powerful γ-ray detectors are revealing fresh details about the interior of the nucleus, focusing initially on cases where there is a large excess of neutrons and edging towards the neutron drip-line limit.

Paramagnons with unexpectedly long lifetimes are observed in the paramagnetic state at temperatures above the antiferromagnetic ordering temperature in TlCuCl₃, posing a challenge to theory.

The standard description of spin–orbit torques neglects geometric phase effects. But recent experiments suggest that the Berry curvature gives rise to an anti-damping torque in systems with broken inversion symmetry.

Understanding the physics of two-dimensional materials beyond graphene is of both fundamental and practical interest. Recent theoretical and experimental advances uncover the interplay between real spin and pseudospins in layered transition metal dichalcogenides.

Gamma-ray bursts are among the most luminous explosions in the cosmos, but the mechanism behind the energetic radiation remains unclear. ‘Fast cooling’ electrons in a decaying magnetic field may offer an explanation.

An argument by contradiction shows that the pseudogap state in the high-temperature superconducting cuprates is due to the superconducting pairing rather than being an independent or even competing state.

Although the concept of a quasiparticle—a particle plus interactions—works very well for some problems, in other cases quasiparticles can be destroyed by quantum fluctuations. Alternative theoretical techniques for handling strong interactions are needed, such as those from string theory.

Quantum criticality is often found in metallic compounds that are close to being magnetic. What about insulators in which the electric moments are fluctuating? These too can be described by the same framework—over a wider temperature range than in quantum critical metals.

The thermal and quantum fluctuations around a quantum critical point can be studied independently by mapping the evolution of the spin dynamics in the critical region of a dimerized quantum magnet using neutron scattering.

When superconducting discs are deposited on graphene they induce local superconducting islands. The phase coupling between the islands can be controlled by a gate. Quantum phase fluctuations kill the superconductivity and lead to a metallic state, however, at higher magnetic fields superconductivity can return.

Spin polarization due to spin–orbit coupling requires broken inversion symmetry. Now, calculations show that the effect arises from local site-asymmetry rather than global space-group asymmetry, and that a hitherto overlooked form of spin polarization should also exist in centrosymmetric structures.

It is now shown that coupled optical microcavities bear all the hallmarks of parity–time symmetry; that is, the system’s dynamics are unchanged by both time-reversal and mirror transformations. The resonant nature of microcavities results in unusual effects not seen in previous photonic analogues of parity–time-symmetric systems: for example, light travelling in one direction is resonantly enhanced but there are no resonance peaks going the other way.

Memories are made of this.