skip to main content

Title: Superconductivity in La2Ni2In
We report here the properties of single crystals of La 2 Ni 2 In . Electrical resistivity and specific heat measurements concur with the results of density functional theory calculations, finding that La 2 Ni 2 In is a weakly correlated metal, where the Ni magnetism is almost completely quenched, leaving only a weak Stoner enhancement of the density of states. Superconductivity is observed at temperatures below 0.9 K. A detailed analysis of the field and temperature dependencies of the resistivity, magnetic susceptibility, and specific heat at the lowest temperatures reveals that La 2 Ni 2 In is a dirty type-II superconductor with likely s -wave gap symmetry. Nanoclusters of ferromagnetic inclusions significantly affect the subgap states resulting in a nonexponential temperature dependence of the specific heat C ( T ) at T ≪ T c .
; ; ;
Award ID(s):
Publication Date:
Journal Name:
Physical review
Page Range or eLocation-ID:
Sponsoring Org:
National Science Foundation
More Like this
  1. A phase transition material, VO 2 , with a semiconductor-to-metal transition (SMT) near 341 K (68 °C) has attracted significant research interest because of drastic changes in its electrical resistivity and optical dielectric properties. To address its application needs at specific temperatures, tunable SMT temperatures are highly desired. In this work, effective transition temperature ( T c ) tuning of VO 2 has been demonstrated via a novel Pt : VO 2 nanocomposite design, i.e. , uniform Pt nanoparticles (NPs) embedded in the VO 2 matrix. Interestingly, a bidirectional tuning has been achieved, i.e. , the transition temperature can be systematically tunedmore »to as low as 329.16 K or as high as 360.74 K, with the average diameter of Pt NPs increasing from 1.56 to 4.26 nm. Optical properties, including transmittance ( T %) and dielectric permittivity ( ε ′) were all effectively tuned accordingly. All Pt : VO 2 nanocomposite thin films maintain reasonable SMT properties, i.e. sharp phase transition and narrow width of thermal hysteresis. The bidirectional T c tuning is attributed to two factors: the reconstruction of the band structure at the Pt : VO 2 interface and the change of the Pt : VO 2 phase boundary density. This demonstration sheds light on phase transition tuning of VO 2 at both room temperature and high temperature, which provides a promising approach for VO 2 -based novel electronics and photonics operating under specific temperatures.« less
  2. Abstract The origin of the weak insulating behavior of the resistivity, i.e. $${\rho }_{xx}\propto {\mathrm{ln}}\,(1/T)$$ ρ x x ∝ ln ( 1 / T ) , revealed when magnetic fields ( H ) suppress superconductivity in underdoped cuprates has been a longtime mystery. Surprisingly, the high-field behavior of the resistivity observed recently in charge- and spin-stripe-ordered La-214 cuprates suggests a metallic, as opposed to insulating, high-field normal state. Here we report the vanishing of the Hall coefficient in this field-revealed normal state for all $$T\ <\ (2-6){T}_{{\rm{c}}}^{0}$$ T < ( 2 − 6 ) T c 0 , where $${T}_{{\rm{c}}}^{0}$$more »T c 0 is the zero-field superconducting transition temperature. Our measurements demonstrate that this is a robust fundamental property of the normal state of cuprates with intertwined orders, exhibited in the previously unexplored regime of T and H . The behavior of the high-field Hall coefficient is fundamentally different from that in other cuprates such as YBa 2 Cu 3 O 6+ x and YBa 2 Cu 4 O 8 , and may imply an approximate particle-hole symmetry that is unique to stripe-ordered cuprates. Our results highlight the important role of the competing orders in determining the normal state of cuprates.« less
  3. To directly use a CO 2 –CH 4 gas mixture for power and CO co-production by proton-conducting solid oxide fuel cells (H-SOFCs), a layer of in situ reduced La 0.6 Sr 0.2 Cr 0.85 Ni 0.15 O 3−δ (LSCrN@Ni) is fabricated on a Ni–BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) anode-supported H-SOFC (H-DASC) for on-cell CO 2 dry reforming of CH 4 (DRC). For demonstrating the effectiveness of LSCrN@Ni, a cell without adding the LSCrN@Ni catalyst (H-CASC) is also studied comparatively. Fueled with H 2 , both H-CASC and H-DASC show similar stable performance with amore »maximum power density ranging from 0.360 to 0.816 W cm −2 at temperatures between 550 and 700 °C. When CO 2 –CH 4 is used as the fuel, the performance and stability of H-CASC decreases considerably with a maximum power density of 0.287 W cm −2 at 700 °C and a sharp drop in cell voltage from the initial 0.49 to 0.10 V within 20 h at 0.6 A cm −2 . In contrast, H-DASC demonstrates a maximum power density of 0.605 W cm −2 and a stable cell voltage above 0.65 V for 65 h. This is attributed to highly efficient on-cell DRC by LSCrN@Ni.« less
  4. Abstract. Ice-nucleating particles (INPs) are efficiently removed fromclouds through precipitation, a convenience of nature for the study of thesevery rare particles that influence multiple climate-relevant cloudproperties including ice crystal concentrations, size distributions andphase-partitioning processes. INPs suspended in precipitation can be used toestimate in-cloud INP concentrations and to infer their originalcomposition. Offline droplet assays are commonly used to measure INPconcentrations in precipitation samples. Heat and filtration treatmentsare also used to probe INP composition and size ranges. Many previousstudies report storing samples prior to INP analyses, but little is knownabout the effects of storage on INP concentration or their sensitivity totreatments. Here,more »through a study of 15 precipitation samples collected at acoastal location in La Jolla, CA, USA, we found INP concentration changes upto > 1 order of magnitude caused by storage to concentrations ofINPs with warm to moderate freezing temperatures (−7 to−19 ∘C). We compared four conditions: (1) storage at roomtemperature (+21–23 ∘C), (2) storage at +4 ∘C, (3) storage at −20 ∘C and (4) flash-freezing samples with liquid nitrogen prior to storage at −20 ∘C. Results demonstrate that storage can lead to bothenhancements and losses of greater than 1 order of magnitude, withnon-heat-labile INPs being generally less sensitive to storage regime, butsignificant losses of INPs smaller than 0.45 µm in all tested storageprotocols. Correlations between total storage time (1–166 d) and changesin INP concentrations were weak across sampling protocols, with theexception of INPs with freezing temperatures ≥ −9 ∘C in samples stored at room temperature. We provide thefollowing recommendations for preservation of precipitation samples fromcoastal or marine environments intended for INP analysis: that samples bestored at −20 ∘C to minimize storage artifacts, thatchanges due to storage are likely an additional uncertainty in INPconcentrations, and that filtration treatments be applied only to freshsamples. At the freezing temperature −11 ∘C, average INPconcentration losses of 51 %, 74 %, 16 % and 41 % were observed foruntreated samples stored using the room temperature, +4, −20 ∘C, and flash-frozen protocols, respectively.Finally, the estimated uncertainties associated with the four storage protocolsare provided for untreated, heat-treated and filtered samples for INPsbetween −9 and −17 ∘C.« less
  5. Modern day data centers are operated at high power for increased power density, maintenance, and cooling which covers almost 2 percent (70 billion kilowatt-hours) of the total energy consumption in the US. IT components and cooling system occupy the major portion of this energy consumption. Although data centers are designed to perform efficiently, cooling the high-density components is still a challenge. So, alternative methods to improve the cooling efficiency has become the drive to reduce the cooling cost. As liquid cooling is more efficient for high specific heat capacity, density, and thermal conductivity, hybrid cooling can offer the advantage ofmore »liquid cooling of high heat generating components in the traditional air-cooled servers. In this experiment, a 1U server is equipped with cold plate to cool the CPUs while the rest of the components are cooled by fans. In this study, predictive fan and pump failure analysis are performed which also helps to explore the options for redundancy and to reduce the cooling cost by improving cooling efficiency. Redundancy requires the knowledge of planned and unplanned system failures. As the main heat generating components are cooled by liquid, warm water cooling can be employed to observe the effects of raised inlet conditions in a hybrid cooled server with failure scenarios. The ASHRAE guidance class W4 for liquid cooling is chosen for our experiment to operate in a range from 25°C – 45°C. The experiments are conducted separately for the pump and fan failure scenarios. Computational load of idle, 10%, 30%, 50%, 70% and 98% are applied while powering only one pump and the miniature dry cooler fans are controlled externally to maintain constant inlet temperature of the coolant. As the rest of components such as DIMMs & PCH are cooled by air, maximum utilization for memory is applied while reducing the number fans in each case for fan failure scenario. The components temperatures and power consumption are recorded in each case for performance analysis« less