41 research outputs found
Second harmonic AC calorimetry technique within a diamond anvil cell
Tuning the energy density of matter at high pressures gives rise to exotic
and often unprecedented properties, e.g., structural transitions,
insulator-metal transitions, valence fluctuations, topological order, and the
emergence of superconductivity. The study of specific heat has long been used
to characterize these kinds of transitions, but their application to the
diamond anvil cell (DAC) environment has proved challenging. Limited work has
been done on the measurement of specific heat within DACs, in part due to the
difficult experimental setup. To this end we have developed a novel method for
the measurement of specific heat within a DAC that is independent of the DAC
design and therefore readily compatible with any DACs already performing high
pressure resistance measurements. As a proof-of-concept, specific heat
measurements of the MgB2 superconductor were performed, showing a clear anomaly
at the transition temperature (Tc), indicative of bulk superconductivity. This
technique allows for specific heat measurements at higher pressure than
previously possible.Comment: 5 pages with 5 figure
Recommended from our members
New Phases and Dissociation-Recombination of Hydrogen Deuteride to 3.4 Mbar
We present infrared absorption studies of solid hydrogen deuteride to pressures as high as 340 GPa (100 GPa ¼ 1 Mbar) in a diamond anvil cell and temperatures in the range 5–295 K. Above 198 GPa the HD sample transforms to a mixture of HD, H2, and D2, interpreted as a process of dissociation and recombination. Three new phase lines are observed, two of which differ remarkably from those of the high pressure homonuclear species, but none are metallic. The time-dependent spectral changes are analyzed to determine the molecular concentrations as a function of time; the nucleon exchange achieves steady state concentrations in ∼20 h at ∼200 GPa.Physic
The 2021 room-temperature superconductivity roadmap.
Designing materials with advanced functionalities is the main focus of contemporary solid-state physics and chemistry. Research efforts worldwide are funneled into a few high-end goals, one of the oldest, and most fascinating of which is the search for an ambient temperature superconductor (A-SC). The reason is clear: superconductivity at ambient conditions implies being able to handle, measure and access a single, coherent, macroscopic quantum mechanical state without the limitations associated with cryogenics and pressurization. This would not only open exciting avenues for fundamental research, but also pave the road for a wide range of technological applications, affecting strategic areas such as energy conservation and climate change. In this roadmap we have collected contributions from many of the main actors working on superconductivity, and asked them to share their personal viewpoint on the field. The hope is that this article will serve not only as an instantaneous picture of the status of research, but also as a true roadmap defining the main long-term theoretical and experimental challenges that lie ahead. Interestingly, although the current research in superconductor design is dominated by conventional (phonon-mediated) superconductors, there seems to be a widespread consensus that achieving A-SC may require different pairing mechanisms.In memoriam, to Neil Ashcroft, who inspired us all