53 research outputs found
Critical role of interlayer dimer correlations in the superconductivity of LaNiO
The recent discovery of superconductivity in LaNiO with
under high pressure opens up a new route to
high- superconductivity. This material realizes a bilayer square
lattice model featuring a strong interlayer hybridization unlike many
unconventional superconductors. A key question in this regard concerns how
electronic correlations driven by the interlayer hybridization affect the
low-energy electronic structure and the concomitant superconductivity. Here, we
demonstrate using a cluster dynamical mean-field theory that the interlayer
electronic correlations (IECs) induce a Lifshitz transition resulting in a
change of Fermi surface topology. By solving an appropriate gap equation, we
further show that the dominant pairing instability (intraorbital
-wave/interorbital -wave) is enhanced by the IECs. The
underlying mechanism is the quenching of a strong ferromagnetic channel,
resulting from the Lifshitz transition driven by the IECs. Our finding
establishes the role of IECs in LaNiO and potentially paves the way
to designing higher-\Tc nickelates
No superconductivity in PbCu(PO)O found in orbital and spin fluctuation exchange calculations
Finding a material that turns superconducting under ambient conditions has
been the goal of over a century of research, and recently
PbCu(PO)O aka LK-99 has been put forward as a possible
contestant. In this work, we study the possibility of electronically driven
superconductivity in LK-99 also allowing for electron or hole doping. We use an
derived two-band model of the Cu orbitals for which
we determine interaction values from the constrained random phase approximation
(cRPA). For this two-band model we perform calculations in the fluctuation
exchange (FLEX) approach to assess the strength of orbital and spin
fluctuations. We scan over a broad range of parameters and enforce no magnetic
or orbital symmetry breaking. Even under optimized conditions for
superconductivity, spin and orbital fluctuations turn out to be too weak for
superconductivity anywhere near to room-temperature. We contrast this finding
to non-self-consistent RPA, where it is possible to induce spin-singlet
-wave superconductivity at K if the system is put
close enough to a magnetic instability.Comment: 6 pages, 3 figure
Coherence length and penetration depth in strongly correlated superconductors
Superconductivity emerges from the spatial coherence of a macroscopic
condensate characterized by two intrinsic length scales: the coherence length
and the London penetration depth . While their
description is well established in weak-coupling Bardeen-Cooper-Schrieffer
(BCS) theory and Eliashberg theory, and are
generally unknown quantities in strongly correlated superconductors. In this
work, we establish a framework to calculate these length scales in microscopic
theories and from first principles. Central to this idea are Nambu-Gor'kov
Green functions under a constraint of finite-momentum pairing and their
analysis with respect to the superconducting order parameter and resultant
supercurrents. We illustrate with a multi-orbital model of alkali-doped
fullerides (AC) using Dynamical Mean-Field Theory (DMFT) how
proximity of superconductivity, Jahn-Teller metallic, and Mott-localized states
impact superconducting coherence, order parameter stiffness, and critical
temperature. Our analysis reveals a "localized" superconducting regime with
robustly short . Multi-orbital effects cause a domeless rise in the
critical temperature as the pairing interaction is increased, setting this
system apart from the BCS to Bose-Einstein-Condensate (BEC) crossover
phenomenology.Comment: main: 12 pages, 3 figures | SM: 19, 6 figure
UV to radio centimetric spectral energy distributions of optically-selected late-type galaxies in the Virgo cluster
We present a multifrequency dataset for an optically-selected,
volume-limited, complete sample of 118 late-type galaxies (>= S0a) in the Virgo
cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio
continuum photometric data as well as spectroscopic data of Halpha, CO and HI
lines, homogeneously reduced, obtained from our own observations or compiled
from the literature. Assuming the energy balance between the absorbed stellar
light and that radiated in the IR by dust, we calibarte an empirical
attenuation law suitable for correcting photometric and spectroscopic data of
normal galaxies. The data, corrected for internal extinction, are used to
construct the spectral energy distribution (SED) of each individual galaxy, and
combined to trace the median SED of galaxies in various classes of
morphological type and luminosity. Low-luminosity, dwarf galaxies have on
average bluer stellar continua and higher far-IR luminosities per unit galaxy
mass than giant, early-type spirals. If compared to nearby starburst galaxies
such as M82 and Arp 220, normal spirals have relatively similar observed
stellar spectra but 10-100 times lower IR luminosities. The temperature of the
cold dust component increases with the far-IR luminosity, from giant spirals to
dwarf irregulars. The SED are used to separate the stellar emission from the
dust emission in the mid-IR regime. We show that the contribution of the
stellar emission at 6.75 micron to the total emission of galaxies is generally
important, from ~ 80% in Sa to ~ 20% in Sc.Comment: 31 pages, 12 figures, 12 tables. Fig 2 avaliable at
(http://goldmine.mib.infn.it/papers/isosed.html). Accepted for publication on
A&
High-resolution radio continuum survey of M33 II. Thermal and nonthermal emission
We determine the variation in the nonthermal radio spectral index in the
nearby spiral galaxy M33 at a linear resolution of 360 pc. We separate the
thermal and nonthermal components of the radio continuum emission without the
assumption of a constant nonthermal spectral index. Using the Spitzer FIR data
at 70 and 160 m and a standard dust model, we deredden the H
emission. The extinction corrected H emission serves as a template for
the thermal free-free radio emission. Subtracting from the observed 3.6 cm and
20 cm emission (Effelsberg and the VLA) this free-free emission, we obtain the
nonthermal maps. A constant electron temperature used to obtain the thermal
radio intensity seems appropriate for M~33 which, unlike the Milky Way, has a
shallow metallicity gradient. For the first time, we derive the distribution of
the nonthermal spectral index across a galaxy, M33. We detect strong nonthermal
emission from the spiral arms and star-forming regions. Wavelet analysis shows
that at 3.6 cm the nonthermal emission is dominated by contributions from
star-forming regions, while it is smoothly distributed at 20 cm. For the whole
galaxy, we obtain thermal fractions of 51% and 18% at 3.6 cm and 20 cm,
respectively. The thermal emission is slightly stronger in the southern than in
the northern half of the galaxy. We find a clear radial gradient of mean
extinction in the galactic plane. The nonthermal spectral index map indicates
that the relativistic electrons suffer energy-loss when diffusing from their
origin in star-forming regions towards interarm regions and the outer parts of
the galaxy. We also conclude that the radio emission is mostly nonthermal at R
5 kpc in M33.Comment: 15 pages, 14 figures, accepted for publication in the Astronomy and
Astrophysics journa
Beta-2-microglobulin Mutations Are Linked to a Distinct Metastatic Pattern and a Favorable Outcome in Microsatellite-Unstable Stage IV Gastrointestinal Cancers
Immune checkpoint blockade (ICB) shows remarkable clinical effects in patients with metastatic microsatellite-unstable (MSI) cancer. However, markers identifying potential non-responders are missing. We examined the prevalence of Beta-2-microglobulin (B2M) mutations, a common immune evasion mechanism, in stage IV MSI gastrointestinal cancer and its influence on metastatic pattern and patients’ survival under ICB. Twenty-five patients with metastatic, MSI gastrointestinal adenocarcinoma were included. Eighteen patients received ICB with pembrolizumab and one patient with nivolumab/ipilimumab. Sequencing was performed to determine B2M mutation status. B2M mutations and loss of B2M expression were detected in 6 out of 25 stage IV MSI cancers. B2M mutations were strongly associated with exclusively peritoneal/peritoneal and lymph node metastases (p=0.0055). However, no significant differences in therapy response (25% vs. 46.6%, p>0.99) and survival (median PFS: 19.5 vs 33.0 months, p=0.74; median OS 39 months vs. not reached, p>0.99) were observed between B2M-mutant and B2M-wild type tumor patients. Among metastatic MSI GI cancers, B2M-mutant tumors represent a biologically distinct disease with distinct metastatic patterns. To assess ICB response in B2M-mutant MSI cancer patients, future studies need to account for the fact that baseline survival of patients with B2M-mutant MSI cancer may be longer than of patients with B2M-wild type MSI cancer
Beta-2-microglobulin Mutations Are Linked to a Distinct Metastatic Pattern and a Favorable Outcome in Microsatellite-Unstable Stage IV Gastrointestinal Cancers
Immune checkpoint blockade (ICB) shows remarkable clinical effects in patients with
metastatic microsatellite-unstable (MSI) cancer. However, markers identifying potential
non-responders are missing. We examined the prevalence of Beta-2-microglobulin (B2M)
mutations, a common immune evasion mechanism, in stage IV MSI gastrointestinal
cancer and its influence on metastatic pattern and patients’ survival under ICB. Twentyfive
patients with metastatic, MSI gastrointestinal adenocarcinoma were included.
Eighteen patients received ICB with pembrolizumab and one patient with nivolumab/
ipilimumab. Sequencing was performed to determine B2M mutation status. B2M
mutations and loss of B2M expression were detected in 6 out of 25 stage IV MSI
cancers. B2M mutations were strongly associated with exclusively peritoneal/peritoneal
and lymph node metastases (p=0.0055). However, no significant differences in therapy
response (25% vs. 46.6%, p>0.99) and survival (median PFS: 19.5 vs 33.0 months,
p=0.74; median OS 39 months vs. not reached, p>0.99) were observed between B2Mmutant
and B2M-wild type tumor patients. Among metastatic MSI GI cancers, B2Mmutant
tumors represent a biologically distinct disease with distinct metastatic patterns.
To assess ICB response in B2M-mutant MSI cancer patients, future studies need to
account for the fact that baseline survival of patients with B2M-mutant MSI cancer may be
longer than of patients with B2M-wild type MSI cancer
ER stress regulates myeloid-derived suppressor cell fate through TRAIL-R–mediated apoptosis
Myeloid-derived suppressor cells (MDSCs) dampen the immune response thorough inhibition of T cell activation and proliferation and often are expanded in pathological conditions. Here, we studied the fate of MDSCs in cancer. Unexpectedly, MDSCs had lower viability and a shorter half-life in tumor-bearing mice compared with neutrophils and monocytes. The reduction of MDSC viability was due to increased apoptosis, which was mediated by increased expression of TNF-related apoptosis–induced ligand receptors (TRAIL-Rs) in these cells. Targeting TRAIL-Rs in naive mice did not affect myeloid cell populations, but it dramatically reduced the presence of MDSCs and improved immune responses in tumor-bearing mice. Treatment of myeloid cells with proinflammatory cytokines did not affect TRAIL-R expression; however, induction of ER stress in myeloid cells recapitulated changes in TRAIL-R expression observed in tumor-bearing hosts. The ER stress response was detected in MDSCs isolated from cancer patients and tumor-bearing mice, but not in control neutrophils or monocytes, and blockade of ER stress abrogated tumor-associated changes in TRAIL-Rs. Together, these data indicate that MDSC pathophysiology is linked to ER stress, which shortens the lifespan of these cells in the periphery and promotes expansion in BM. Furthermore, TRAIL-Rs can be considered as potential targets for selectively inhibiting MDSCs
- …