28 research outputs found
Evidence for Fermi surface reconstruction in the static stripe phase of LaEuSrCuO,
We present a photoemission study of LaEuSrCuO
with doping level =1/8, where the charge carriers are expected to order
forming static stripes. Though the local probes in direct space seem to be
consistent with this idea, there has been little evidence found for such
ordering in quasiparticle dispersions. We show that the Fermi surface topology
of the 1/8 compound develops notable deviations from that observed for LaSrCuO in a way consistent with the FS reconstruction expected for
the scattering on the antiphase stripe order
Charge-Stripe Order and Superconductivity in
A combined resistivity and hard x-ray diffraction study of superconductivity
and charge ordering in , as a function of Pt
substitution and externally applied hydrostatic pressure, is presented.
Experiments are focused on samples near the critical composition where competition and switching between charge order and
superconductivity is established. We show that charge order as a function of
pressure in is preempted - and hence
triggered - by a structural transition. Charge ordering appears uniaxially
along the short crystallographic (1,0,1) domain axis with a
modulation. Based on these results we
draw a charge-order phase diagram and discuss the relation between stripe
ordering and superconductivity.Comment: 8 pages, 4 figures: Accepted in Scientific Report
Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates
We present a soft x-ray angle-resolved photoemission spectroscopy study of
the overdoped high-temperature superconductors LaSrCuO and
LaEuSrCuO. In-plane and out-of-plane components of
the Fermi surface are mapped by varying the photoemission angle and the
incident photon energy. No dispersion is observed along the nodal
direction, whereas a significant antinodal dispersion is identified.
Based on a tight-binding parametrization, we discuss the implications for the
density of states near the van-Hove singularity. Our results suggest that the
large electronic specific heat found in overdoped LaSrCuO can
not be assigned to the van-Hove singularity alone. We therefore propose quantum
criticality induced by a collapsing pseudogap phase as a plausible explanation
for observed enhancement of electronic specific heat
Microwave analysis of the interplay between magnetism and superconductivity in EuFe2(As1−xPx)2 single crystals
We report on the microwave analysis of the interplay between magnetism and superconductivity in single crystals of EuFe_{2}(As_{1−x}P_{x})_{2}, accomplished by means of a coplanar waveguide resonator technique. The bulk complex magnetic susceptibility χ_{m} extracted through a cavity perturbation approach is demonstrated to be highly sensitive to the magnetic structure and dynamics, revealing two distinct magnetic transitions below the superconducting critical temperature. By a comparison with magnetic force microscopy maps, we ascribe the χ_{m}^{′′} peak observed at about 17 K to the transition from the ferromagnetic domain Meissner phase to the domain vortex-antivortex state, with the subsequent evolution of the domain structure at lower temperatures. The second χ_{m}^{′′} peak observed at 11 K reflects a specific high-frequency feature, connected to vortex-antivortex dynamics and eventual spin reorientation transition of the Eu^{2+} canted ferromagnetic subsystem. The two peaks merge and vanish upon application of an in-plane magnetic field, which is compatible with the presence of a quantum critical point below 1 T
Direct observation of orbital hybridisation in a cuprate superconductor
The minimal ingredients to explain the essential physics of layered
copper-oxide (cuprates= materials remains heavily debated. Effective low energy
single-band models of the copper-oxygen orbitals are widely used because there
exists no strong experimental evidence supporting multiband structures. Here we
report angle-resolved photoelectron spectroscopy experiments on La-based
cuprates that provide direct observation of a two-band structure. This
electronic structure, qualitatively consistent with density functional theory,
is parametrised by a two-orbital ( and ) tight-binding
model. We quantify the orbital hybridisation which provides an explanation for
the Fermi surface topology and the proximity of the van-Hove singularity to the
Fermi level. Our analysis leads to a unification of electronic hopping
parameters for single-layer cuprates and we conclude that hybridisation,
restraining d-wave pairing, is an important optimisation element for
superconductivity.Comment: supplementary material available on reques
ULK1 inhibition overcomes compromised antigen presentation and restores antitumor immunity in LKB1-mutant lung cancer
Inactivating mutations in LKB1/STK11 are present in roughly 20% of nonsmall cell lung cancers (NSCLC) and portend poor response to anti-PD-1 immunotherapy. Unexpectedly, we found that LKB1 deficiency correlated with elevated tumor mutational burden (TMB) in NSCLCs from nonsmokers and genetically engineered mouse models, despite the frequent association between high-TMB and anti-PD-1 treatment efficacy. However, LKB1 deficiency also suppressed antigen processing and presentation, which are associated with compromised immunoproteasome activity and increased autophagic flux. Immunoproteasome activity and antigen presentation were restored by inhibiting autophagy through targeting the ATG1/ULK1 pathway. Accordingly, ULK1 inhibition synergized with PD-1 antibody blockade, provoking effector T-cell expansion and tumor regression in Lkb1-mutant tumor models. This study reveals an interplay between the immunoproteasome and autophagic catabolism in antigen processing and immune recognition, and proposes the therapeutic potential of dual ULK1 and PD-1 inhibition in LKB1-mutant NSCLC as a strategy to enhance antigen presentation and to promote antitumor immunity
Band structure of overdoped cuprate superconductors:Density functional theory matching experiments
A comprehensive angle resolved photoemission spectroscopy study of the band
structure in single layer cuprates is presented with the aim of uncovering
universal trends across different materials. Five different hole- and
electron-doped cuprate superconductors
(LaEuSrCuO, LaSrCuO,
BiPbSrCuO,
TlBaCuO, and
PrLaCeCuO) have been studied with special focus
on the bands with predominately -orbital character. Using light polarization
analysis, the and bands are identified across these materials. A
clear correlation between the band energy and the apical oxygen
distance is demonstrated. Moreover, the compound dependence of
the band bottom and the band top is revealed. Direct
comparison to density functional theory (DFT) calculations employing hybrid
exchange-correlation functionals demonstrates excellent agreement. We thus
conclude that the DFT methodology can be used to describe the global band
structure of overdoped single layer cuprates on both the hole and electron
doped side