46 research outputs found
Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdOFBiS
We present a combined growth and transport study of superconducting
single-crystalline NdOFBiS. Evidence of two-dimensional
superconductivity with significant phase fluctuations of preformed Cooper pairs
preceding the superconducting transition is reported. This result is based on
three key observations. (1) The resistive superconducting transition
temperature (defined by resistivity ) increases with
increasing disorder. (2) As , the conductivity diverges
significantly faster than what is expected from Gaussian fluctuations in two
and three dimensions. (3) Non-Ohmic resistance behavior is observed in the
superconducting state. Altogether, our observations are consistent with a
temperature regime of phase-fluctuating superconductivity. The crystal
structure with magnetic ordering tendencies in the NdOF layers
and (super)conductivity in the BiS layers is likely responsible for the
two-dimensional phase fluctuations. As such, NdOFBiS falls
into the class of unconventional ``laminar" bulk superconductors that include
cuprate materials and 4Hb-TaS
Revealing the Orbital Composition of Heavy Fermion Quasiparticles in CeRu2Si2
We present a resonant angle-resolved photoemission spectroscopy (ARPES) study of the electronic band structure and heavy fermion quasiparticles in CeRu2Si2. Using light polarization analysis, considerations of the crystal field environment and hybridization between conduction and f electronic states, we identify the d-electronic orbital character of conduction bands crossing the Fermi level. Resonant ARPES spectra suggest that the localized Ce f states hybridize with eg and t2g states around the zone center. In this fashion, we reveal the orbital structure of the heavy fermion quasiparticles in CeRu2Si2 and discuss its implications for metamagnetism and superconductivity in the related compound CeCu2Si2
Pseudogap suppression by competition with superconductivity in La-based cuprates
We carried out a comprehensive high-resolution angle-resolved photoemission spectroscopy (ARPES) study of the pseudogap interplay with superconductivity in La-based cuprates. The three systems La2−xSrxCuO4, La1.6−xNd0.4SrxCuO4, and La1.8−xEu0.2SrxCuO4 display slightly different pseudogap critical points in the temperature versus doping phase diagram. We studied the pseudogap evolution into the superconducting state for doping concentrations just below the critical point. In this setting, near optimal doping for superconductivity and in the presence of the weakest possible pseudogap, we uncover how the pseudogap is partially suppressed inside the superconducting state. This conclusion is based on the direct observation of a reduced pseudogap energy scale and re-emergence of spectral weight suppressed by the pseudogap. Altogether these observations suggest that the pseudogap phenomenon in La-based cuprates is in competition with superconductivity for antinodal spectral weight
Pseudogap Suppression by Competition with Superconductivity in La-Based Cuprates
We have carried out a comprehensive high-resolution angle-resolved
photoemission spectroscopy (ARPES) study of the pseudogap interplay with
superconductivity in La-based cuprates. The three systems
LaSrCuO, LaNdSrCuO, and
LaEuSrCuO display slightly different pseudogap
critical points in the temperature versus doping phase diagram. We have studied
the pseudogap evolution into the superconducting state for doping
concentrations just below the critical point. In this setting, near optimal
doping for superconductivity and in the presence of the weakest possible
pseudogap, we uncover how the pseudogap is partially suppressed inside the
superconducting state. This conclusion is based on the direct observation of a
reduced pseudogap energy scale and re-emergence of spectral weight suppressed
by the pseudogap. Altogether these observations suggest that the pseudogap
phenomenon in La-based cuprates is in competition with superconductivity for
anti-nodal spectral weight
The regulatory mechanisms of NG2/CSPG4 expression
Neuron-glial antigen 2 (NG2), also known as chondroitin sulphate proteoglycan 4 (CSPG4), is a surface type I transmembrane core proteoglycan that is crucially involved in cell survival, migration and angiogenesis. NG2 is frequently used as a marker for the identification and characterization of certain cell types, but little is known about the mechanisms regulating its expression. In this review, we provide evidence that the regulation of NG2 expression underlies inflammation and hypoxia and is mediated by methyltransferases, transcription factors, including Sp1, paired box (Pax) 3 and Egr-1, and the microRNA miR129-2. These regulatory factors crucially determine NG2-mediated cellular processes such as glial scar formation in the central nervous system (CNS) or tumor growth and metastasis. Therefore, they are potential targets for the establishment of novel NG2-based therapeutic strategies in the treatment of CNS injuries, cancer and other conditions of these types
Duplicate Detection and Deletion in the Extended NF² Data Model
A current research topic in the area of relational databases is the design of systems based on the Non First Normal Form (NF ) data model. One particular development, the so-called extended NF data model, even permits structured values like lists and tuples to be included as attributes in relations. It is thus well suited to represent complex objects for non-standard database applications. A DBMS which uses this model, called the Advanced Information Management Prototype, is currently being implemented at the IBM Heidelberg Scientific Center. In this paper we examine the problem of detecting and deleting duplicates within this data model. Several alternative approaches are evaluated and a new method, based on sorting complex objects, is proposed, which is both time- and space-efficient