The properties of quantum materials are commonly tuned using experimental variables such as pressure, magnetic field and doping. Here we explore a different approach using irreversible, plastic ...deformation of single crystals. We show that compressive plastic deformation induces low-dimensional superconductivity well above the superconducting transition temperature (T
) of undeformed SrTiO
, with evidence of possible superconducting correlations at temperatures two orders of magnitude above the bulk T
. The enhanced superconductivity is correlated with the appearance of self-organized dislocation structures, as revealed by diffuse neutron and X-ray scattering. We also observe deformation-induced signatures of quantum-critical ferroelectric fluctuations and inhomogeneous ferroelectric order using Raman scattering. Our results suggest that strain surrounding the self-organized dislocation structures induces local ferroelectricity and quantum-critical dynamics that strongly influence T
, consistent with a theory of superconductivity enhanced by soft polar fluctuations. Our results demonstrate the potential of plastic deformation and dislocation engineering for the manipulation of electronic properties of quantum materials.
Abstract
The interplay between structural and electronic degrees of freedom in complex materials is the subject of extensive debate in physics and materials science. Particularly interesting ...questions pertain to the nature and extent of pre-transitional short-range order in diverse systems ranging from shape-memory alloys to unconventional superconductors, and how this microstructure affects macroscopic properties. Here we use neutron and X-ray diffuse scattering to uncover universal structural fluctuations in La
2-x
Sr
x
CuO
4
and Tl
2
Ba
2
CuO
6+δ
, two cuprate superconductors with distinct point disorder effects and with optimal superconducting transition temperatures that differ by more than a factor of two. The fluctuations are present in wide doping and temperature ranges, including compositions that maintain high average structural symmetry, and they exhibit unusual, yet simple scaling behaviour. The scaling regime is robust and universal, similar to the well-known critical fluctuations close to second-order phase transitions, but with a distinctly different physical origin. We relate this behaviour to pre-transitional phenomena in a broad class of systems with structural and magnetic transitions, and propose an explanation based on rare structural fluctuations caused by intrinsic nanoscale inhomogeneity. We also uncover parallels with superconducting fluctuations, which indicates that the underlying inhomogeneity plays an important role in cuprate physics.
The doped perovskite BaBiO
exhibits a maximum superconducting transition temperature (T
) of 34 K and was the first high-T
oxide to be discovered, yet pivotal questions regarding the nature of both ...the metallic and superconducting states remain unresolved. Although it is generally thought that superconductivity in the bismuthates is of the conventional s-wave type, the pairing mechanism is still debated, with strong electron-phonon coupling and bismuth valence or bond disproportionation possibly playing a role. Here we use diffuse x-ray scattering and Monte Carlo modeling to study the local structure of Ba
K
BiO
across its insulator-metal boundary. We find no evidence for either long- or short-range disproportionation, which resolves a major conundrum, as disproportionation and the related polaronic effects are likely not relevant for the metallic and superconducting states. Instead, we uncover nanoscale structural correlations that break inversion symmetry, with far-reaching implications for the electronic physics. This unexpected finding furthermore establishes that the bismuthates belong to the broader classes of materials with hidden spin-orbit coupling and a tendency towards inversion-breaking displacements.
Abstract
The doped perovskite BaBiO
3
exhibits a maximum superconducting transition temperature (
T
c
) of 34 K and was the first high-
T
c
oxide to be discovered, yet pivotal questions regarding the ...nature of both the metallic and superconducting states remain unresolved. Although it is generally thought that superconductivity in the bismuthates is of the conventional
s
-wave type, the pairing mechanism is still debated, with strong electron-phonon coupling and bismuth valence or bond disproportionation possibly playing a role. Here we use diffuse x-ray scattering and Monte Carlo modeling to study the local structure of Ba
1-x
K
x
BiO
3
across its insulator-metal boundary. We find no evidence for either long- or short-range disproportionation, which resolves a major conundrum, as disproportionation and the related polaronic effects are likely not relevant for the metallic and superconducting states. Instead, we uncover nanoscale structural correlations that break inversion symmetry, with far-reaching implications for the electronic physics. This unexpected finding furthermore establishes that the bismuthates belong to the broader classes of materials with hidden spin-orbit coupling and a tendency towards inversion-breaking displacements.
A new method of regenerating dehumidification solution is developed, which releases the dilute solution into vacuum to improve water evaporation instead of the traditional methods. Experiments on the ...temperature distribution in the lithium chloride solution droplets were carried out on the basis of the theoretical analysis. The experimental results indicate that both the surface temperature and center temperature declined sharply in the beginning stage of flash evaporation, then recover slowly, even though sometimes one is higher than the other in the whole process; pressure is the core factor of evaporation rate, the lower the pressure, the more intense flash; droplets with higher initial temperature only strengthen the intensity of the flash evaporation at the beginning. Radiant heat can significantly promote the strength of the flash evaporation which cannot be neglected especially for single droplet. The contrast between the experimental results and the numerical results prove that droplet flash evaporation model can be applied to the process without radiation, and the numerical results should be amended when used on the radiation condition.
Liquid desiccant indirect evaporative cooling is an ideal alternative system for conventional vapor compression systems to meet new economic, environmental, and regulatory challenges. This ...alternative system consists of two air-handling processes: moisture removal in the dehumidifier and sensible heat removal in the M-cycle indirect evaporative cooler. The performance of the first stage influences the cooling capacity of the second stage. SHR (sensible load divided by total load), dew point effectiveness, moisture reduction, and temperature reduction were adopted as indices to describe the heat and mass transfer performance of the integrated liquid desiccant and the M-cycle indirect evaporative cooler. The effects of air and desiccant inlet parameters, as well as the working air ratio, on the performance of the hybrid were experimentally investigated. The results showed that the variation of dehumidification capacity in the first stage directly affected the cooling capacity in the second stage when increasing the inlet parameters of the air or desiccant. The energy balance in both the dehumidifier and the M-cycle indirect evaporative cooler were in the range of ±20% for all the experiment runs. To achieve performance in the second stage, the supplied water flow rate to the wick surface had to be approximately five times that of the evaporative water.
BARREL is a multiple-balloon investigation designed to study electron losses from Earth’s Radiation Belts. Selected as a NASA Living with a Star Mission of Opportunity, BARREL augments the Radiation ...Belt Storm Probes mission by providing measurements of relativistic electron precipitation with a pair of Antarctic balloon campaigns that will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (∼20 kg) stratospheric balloons will be successively launched to maintain an array of ∼5 payloads spread across ∼6 hours of magnetic local time in the region that magnetically maps to the radiation belts. Each balloon carries an X-ray spectrometer to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in the atmosphere, and a DC magnetometer to measure ULF-timescale variations of the magnetic field. BARREL will provide the first balloon measurements of relativistic electron precipitation while comprehensive in situ measurements of both plasma waves and energetic particles are available, and will characterize the spatial scale of precipitation at relativistic energies. All data and analysis software will be made freely available to the scientific community.
Flash evaporation, as a new method to regenerate dehumidification solution, is investigated in this paper. Droplets of lithium chloride and/or calcium chloride solution were suspended on the junction ...of a thermocouple, whose characteristic change was captured by high-speed camera, infrared camera, and thermocouple, and analyzed by comparing the values of different conditions. The results indicate that the pressure determines the degree of superheat, and the absorbed heat affects the intensity of the evaporation. A stronger surface tension caused by an increase in concentration or in change of solute weakens the intensity of water evaporation; a higher initial droplet temperature improves the evaporation intensity in the beginning stage, having no influence on its final temperature. The smaller the droplet diameter, the lower the minimum temperature is; radiant heat plays a decisive role in the process of flash evaporation, which is almost the only heat source provided to the droplet for evaporation in the stable stage.
•Flash evaporation, as a new method to regenerate liquid desiccant, is investigated.•Characteristic change is analyzed by comparing the values of different conditions.•Pressure determines the degree of superheat.•Absorbed heat affects the intensity of the evaporation.•Radiant heat plays a decisive role in the process of flash evaporation.
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