Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
It has been 20 years since the fall of the Berlin Wall. In the wake of the upheaval, the East German society was radically remodelled. For physicists, it brought new opportunities — and fresh challenges.
A spectroscopic technique that enables momentum-resolved probing of excitations of atomic gases in optical lattices allows the full band structure of such systems to be measured for the first time. The method should facilitate the comparison of quantum-gas phases with their condensed-matter counterparts.
When a Van Hove singularity exists near the Fermi energy of a solid’s density of states, it can cause a variety of exotic phenomena to emerge. Scanning tunnelling microscope measurements indicate that when graphite’s graphene sheets are rotated out of their usual alignment, it can generate low-energy Van Hove singularities for which the position is controlled by the angle of rotation.
The composition of integral quantum number particles such as protons and neutrons from the strong confinement of fractional quantum number particles such as quarks is well known in high-energy physics. Now, similar behaviour has been found in condensed-matter physics, in the excitation spectra of a weakly coupled spin-ladder compound.
X-ray sources such as free-electron lasers offer the potential to study matter at unprecedented spatial and temporal resolution. But that potential is limited by the poor quality of conventional X-ray optical elements. An in situ technique that corrects for wavefront aberrations and allows X-rays to be focused to a spot just 7 nm wide could provide a solution.
High-temperature superconductivity in the cuprates arises when charge carriers are added to an insulator. Between these states lies the so-called nodal liquid at low temperature. Photoemission spectroscopy suggests that superconductivity evolves smoothly from this nodal-liquid state.
A simple programmable quantum processor has been created using trapped atomic ions. The system can be programmed with 15 classical inputs to produce any unitary operation on two qubits. This trapped-ion approach is amenable to scaling up for creating more complex circuits.
The transition from a ferromagnetic to a paramagnetic state is observed directly as the density of carriers that mediate spin–spin coupling is varied. The measurement was performed on thin films of GaMnAs and was made possible by superconducting quantum interference devices (SQUIDS).
The Nernst effect—the generation of a transverse electric field in a system subject to a longitudinal temperature gradient and perpendicular magnetic field—is increasingly used as a probe of a material’s electronic structure. The discovery of an unexpected Nernst response in graphite establishes the role of dimensionality on this effect, and enables the individual contributions of bulk and surface to be distinguished.
There is considerable debate over the size and direction of the non-adiabatic component of the spin-torque generated when a current flows across a domain wall in a ferromagnet. Measurements of this property in a wall just 1–10 nm wide suggest its value is small, arising from purely magnetic dissipation mechanisms.
Measurements of the melting point of diamond at pressures of around 10 million atm suggest it could be present in crystalline form in the interiors of giant planets. At even higher pressures and temperatures about 50,000 K, diamond melts to form an unexpectedly complex, polymer-like fluid phase.
Cold atoms and photons confined together in high-quality optical resonators self-organize into complicated crystalline structures that have an optical-wavelength scale. Complex solid-state phenomena can be studied in real time on directly observable scales.
Proliferation of so-called anyonic defects in a topological phase of quantum matter leads to a critical state that can be visualized as a 'quantum foam', with topology-changing fluctuations on all length scales.
The discovery of iron-based pnictide superconductors may have reinvigorated the field of high-temperature superconductivity, but the cuprate superconductors are still in the game.
