More to read in physica status solidi (b)

S. G. Pavlov, R. Kh. Zhukavin, V. N. Shastin, and H.-W. Hübers The physical principles of terahertz silicon lasers based on intracenter transitions [Review Article] Phys. Status Solidi B 250(1), 9–36 (2013), DOI 10.1002/pssb.201248322 Many optoelectronic applications of silicon are hampered by the indirect band gap of the material; however, laser transitions between localized impurity levels are attracting attention due to their potential to conquer the otherwise poorly covered terahertz spectral range. Pavlov et al. review the current state-of-the-art of this field. They contrast lasing processes that are attributed to optical transitions between donor states with those due to Raman-type scattering and point to optical-loss mechanisms that are dominant in the terahertz spectral range.

Qimiao Si and Silke Paschen Quantum phase transitions in heavy fermion metals and Kondo insulators [Review Article] Phys. Status Solidi B 250(3), 425–438 (2013), DOI 10.1002/pssb.201300005 Si and Paschen address quantum phase transitions in strongly correlated electron systems, i.e. phase transitions occurring at absolute zero temperature, as function of a non-thermal tuning parameter such as magnetic field, pressure, or doping. When the transitions are continuous, the accompanying quantum critical fluctuations drastically modify the materials properties at finite temperatures: they can turn a normal metal into a non-Fermi liquid, or a poor conductor into an unconventional superconductor. The authors review the highly active theoretical and experimental research on quantum criticality in antiferromagnetic heavy fermion systems, and extend the discussion to less explored settings such as Kondo insulating, mixed valent, ferromagnetic, quadrupolar, or spin-glass systems.

Giacomo Prando, Samuele Sanna, Gianrico Lamura, Toni Shiroka, Matteo Tropeano, Andrea Palenzona, Hans-Joachim Grafe, Bernd Büchner, Pietro Carretta, and Roberto De Renzi Phase separation at the magnetic–superconducting transition in La0.7Y0.3FeAsO1–xFx [Original Paper] Phys. Status Solidi B 250(3), 599–602 (2013), DOI 10.1002/pssb.201200767 Prando et al. report a detailed µ+SR and 19F-NMR study of the La0.7Y0.3FeAsO1–xFx class of materials. Here, the diamagnetic La1–yYy substitution increases chemical pressure and, accordingly, sizeably enhances the optimal superconducting transition temperature. The authors investigate the magnetic–superconducting phase transition by keeping the Y content constant (y = 0.3) and by varying the F content in the range 0.025 ≤ x ≤ 0.15. The results show how magnetism and superconductivity coexist for x = 0.065. Such coexistence is due to segregation of the two phases in macroscopic regions.

Markus Heyde, Georg H. Simon, and Leonid Lichtenstein Resolving oxide surfaces – From point and line defects to complex network structures [Feature Article] Phys. Status Solidi B 250(5), 895–921 (2013), DOI 10.1002/pssb.201248597 The determination of structure has always been in the focus of the scientific community. Still, diffraction methods are powerful tools in the field of surface science. However, they have limitations when it comes to the analysis of complex structures or materials without periodicity and order. This topic is clearly visible in the Feature Article by Markus Heyde et al. Here, the authors present how they have applied state of the art atomic force and scanning tunneling microscopy to verify oxide film structures ranging from zero-dimensional (0D) point defects, one-dimensional (1D) line defects to two-dimensional (2D) random networks, i.e. amorphous structures. The latter example has fully demonstrated the validity of Zachariasen’s postulation and thereby unraveled for the first time the real-space structure of an amorphous solid in all of its details.

Ioannis Deretzis and Antonino La Magna Process simulation of hydrogen intercalation in epitaxial graphene on SiC(0001) [Original Paper] Phys. Status Solidi B 250(8), 1478–1482 (2013), DOI 10.1002/pssb.201200970 The simulation of processes is a fundamental feature of the technological computer-aided design, aiming at a fast and costless development of hi-tech products. Its extension to graphene could be essential for the predictive control of innovative technologies based on this material. Deretzis and La Magna demonstrate an example of such computational methodology, applied to the study of the intercalation steps for epitaxial graphene exposed to a hydrogen-rich gaseous ambient. The simulation framework is a superlattice event-driven Kinetic Monte Carlo algorithm appropriately formulated with ab initio energetics.

Justin P. Bergfield and Mark A. Ratner Forty years of molecular electronics: Non-equilibrium heat and charge transport at the nanoscale [Review Article] Phys. Status Solidi B 250(11), 2249–2266 (2013), DOI 10.1002/pssb.201350048 Even after forty years of progress, the vibrant field of molecular electronics is still breaking new ground both experimentally and theoretically. The unique and complex interplay between molecular structure and the flow of charge, heat, and spin ensures a rich future for both fundamental research and possible device applications. In their review, Bergfield and Ratner address some of the history and recent advances in the field of molecular electronics and propose six major areas where they believe the field is evolving, and in which they expect to see exciting work in the years and decades ahead. As an example of an emerging topic, the second half of this review is devoted to molecular thermoelectrics.

Aravind Vijayaraghavan Bottom-up assembly of nano-carbon devices by dielectrophoresis [Feature Article] Phys. Status Solidi B 250(12), 2505–2517 (2013), DOI 10.1002/pssb.201300565 This Feature Article reviews the development and applications of dielectrophoresis (DEP) towards carbon nanotube (CNT) and graphene devices. DEP was first used to separate metallic and semiconducting CNTs, but has since then emerged as a leading route to large-scale directed assembly of nano-carbons. In addition to field-effect transistors, DEP-assembled devices have been demonstrated for sensors, optoelectronics and resonators. DEP is a bottom–up assembly route, and could pose a challenge to conventional top–down fabrication for nano-carbon electronics.

Ladislav Kavan, Jun-Ho Yum, and Michael Graetzel Application of graphene-based nanostructures in dye-sensitized solar cells [Invited Article] Phys. Status Solidi B 250(12), 2643–2648 (2013), DOI 10.1002/pssb.201300064 Kavan et al. review recent advances in the application of graphene and related materials, viz. graphene nanoplatelets, functionalized graphene sheets, graphene oxide, and reduced graphene oxide as electrode building materials in dye sensitized solar cells. Graphene promises multifaceted use as prospective sensitizer, photoanode additive, current collector, and electrocatalyst for the redox-shuttle turnover. Of particular significance is the use of graphene as cathode catalyst in state-of-the-art cobalt-mediated solar cells, where it can successfully replace platinum.