A normal metal exhibits a valence plasmon, which is a sound wave in its conduction electron density. The mysterious strange metal is characterized by non-Boltzmann transport and violates most ...fundamental Fermi-liquid scaling laws. A fundamental question is, do strange metals have plasmons? Using momentum-resolved inelastic electron scattering, we recently showed that, rather than a plasmon, optimally dopedBi2.1Sr1.9Ca1.0Cu2.0O8+x (Bi-2212) exhibits a featureless, temperature-independent continuum with a power-law form over most energy and momentum scales M. Mitrano et al., Proc. Natl. Acad. Sci. U.S.A. 115, 5392 (2018). Here, we show that this continuum is present throughout the fan-shaped, strange metal region of the phase diagram. Outside this region, dramatic changes in spectral weight are observed: In underdoped samples, spectral weight up to 0.5 eV is enhanced at low temperature, biasing the system toward a charge order instability. The situation is reversed in the overdoped case, where spectral weight is strongly suppressed at low temperature, increasing quasiparticle coherence in this regime. Optimal doping corresponds to the boundary between these two opposite behaviors at which the response is temperature independent. Our study suggests that plasmons do not exist as well-defined excitations in Bi-2212 and that a featureless continuum is a defining property of the strange metal, which is connected to a peculiar crossover where the spectral weight change undergoes a sign reversal.
The detection of recurrent mutations affecting the hormone binding domain (HBD) of estrogen receptor alpha (ERα/ESR1) in endocrine therapy-resistant and metastatic breast cancers has prompted ...interest in functional characterization of these genetic alterations. Here, we explored the role of HBD-ESR1 mutations in influencing the behavior of breast cancer stem cells (BCSCs), using various BC cell lines stably expressing wild-type or mutant (Y537 N, Y537S, D538G) ERα. Compared to WT-ERα clones, mutant cells showed increased CD44+/CD24- ratio, mRNA levels of stemness genes, Mammosphere Forming Efficiency (MFE), Self-Renewal and migratory capabilities. Mutant clones exhibited high expression of NOTCH receptors/ligands/target genes and blockade of NOTCH signaling reduced MFE and migratory potential. Mutant BCSC activity was dependent on ERα phosphorylation at serine 118, since its inhibition decreased MFE and NOTCH4 activation only in mutant cells. Collectively, we demonstrate that the expression of HBD-ESR1 mutations may drive BC cells to acquire stem cell traits through ER/NOTCH4 interplay. We propose the early detection of HBD-ESR1 mutations as a challenge in precision medicine strategy, suggesting the development of tailored-approaches (i.e. NOTCH inhibitors) to prevent disease development and metastatic spread in BC mutant-positive patients.
•ESR1 hormone binding domain mutations increase breast cancer stem cell activity.•NOTCH activation promotes stemness phenotype in mutant-positive breast cancer cells.•ERα S118 phosphorylation sustains NOTCH activation and stemness in mutant clones.•NOTCH-tailored therapy may be suitable in breast cancer mutant-positive patients.
Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers possess excellent dielectric, mechanical properties and heat resistance. However, the surface of PBO fibers is smooth and highly chemical inert, ...resulting in poor interfacial compatibility to polymer matrix, which severely limits its wider application in high-performance fiber-reinforced resin matrix composites. In this work, random copolymers (P(S-co-BCB-co-MMA)) containing benzocyclobutene in the side-chain were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, which were then utilized to form dense random copolymer membrane on the surface of PBO fibers by thermally cross-linking at 250 °C (PBO@P fibers). Four kinds of synthesized P(S-co-BCB-co-MMA) with different number-average molar mass (Mn) were well controlled and possessed narrow dispersity. When the Mn was 32300, the surface roughness of PBO@P fibers was increased from 11 nm (PBO fibers) to 39 nm. In addition, PBO@P fibers presented the optimal interfacial compatibility with bisphenol A cyanate (BADCy) resins. And the single fiber pull-out strength of PBO@P fibers/BADCy micro-composites was 4.5 MPa, increasing by 45.2% in comparison with that of PBO fibers/BADCy micro-composites (3.1 MPa). Meantime, PBO@P fibers still retained excellent tensile strength (about 5.1 GPa). Overall, this work illustrates a simple and efficient surface functionalization method, which would provide a strong theoretical basis and technical support for controlling the surface structure & chemistry of inert substrates.
The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, ...spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
Abstract
The superconducting state is formed by the condensation of Cooper pairs and protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair ...determines the gap function. Thus, it is pivotal to detect the gap structure for understanding the mechanism of superconductivity. In cuprate superconductors, it has been well established that the gap may have a
d
-wave function. This gap function has an alternative sign change in the momentum space. It is however hard to visualize this sign change. Here we report the measurements of scanning tunneling spectroscopy in Bi
2
Sr
2
CaCu
2
O
8+δ
and conduct the analysis of phase-referenced quasiparticle interference (QPI). We see the seven basic scattering vectors that connect the octet ends of the banana-shaped contour of Fermi surface. The phase-referenced QPI clearly visualizes the sign change of the
d
-wave gap. Our results illustrate an effective way for determining the sign change of unconventional superconductors.
Abstract
The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the ...Dirac semimetal ZrTe
5
. It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe
5
samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe
5
electronic structure and its Dirac-type semi-metallic character.
Competition between magnetism and the kinetic energy of mobile carriers (typically holes) in doped antiferromagnets may lead to 'stripe' phases, which are charged rivers separating regions of ...oppositely phased antiferromagnetism. In copper oxides the main experimental evidence for such coexisting static spin and charge order comes from neutron scattering in La1.48 Nd0.4 Sr0.12 CuO4 (LNSCO; ref. 5) and La1.875 Ba0.125 CuO4 (LBCO; ref. 6). However, as a neutron is neutral, it does not detect charge but rather its associated lattice distortion, so it is not known whether the stripes involve ordering of the doped holes. Here we present a study of the charge order in LBCO with resonant soft X-ray scattering (RSXS). We observe giant resonances near the Fermi level as well as near the correlated gap, demonstrating significant modulation in both the doped-hole density and the 'Mottness', or the degree to which the system resembles a Mott insulator. The peak-to-trough amplitude of the valence modulation is estimated to be 0.063 holes, which suggests an integrated area of 0.59 holes under a single stripe, close to the expected 0.5 for half-filled stripes.
Abstract
The quantum limit (QL) of an electron liquid, realised at strong magnetic fields, has long been proposed to host a wealth of strongly correlated states of matter. Electronic states in the QL ...are, for example, quasi-one dimensional (1D), which implies perfectly nested Fermi surfaces prone to instabilities. Whereas the QL typically requires unreachably strong magnetic fields, the topological semimetal ZrTe
5
has been shown to reach the QL at fields of only a few Tesla. Here, we characterize the QL of ZrTe
5
at fields up to 64 T by a combination of electrical-transport and ultrasound measurements. We find that the Zeeman effect in ZrTe
5
enables an efficient tuning of the 1D Landau band structure with magnetic field. This results in a Lifshitz transition to a 1D Weyl regime in which perfect charge neutrality can be achieved. Since no instability-driven phase transitions destabilise the 1D electron liquid for the investigated field strengths and temperatures, our analysis establishes ZrTe
5
as a thoroughly understood platform for potentially inducing more exotic interaction-driven phases at lower temperatures.
Quantum materials are amenable to nonequilibrium manipulation with light, enabling modification and control of macroscopic properties. Light-based augmentation of superconductivity is particularly ...intriguing. Copper-oxide superconductors exhibit complex interplay between spin order, charge order, and superconductivity, offering the prospect of enhanced coherence by altering the balance between competing orders. We utilize terahertz time-domain spectroscopy to monitor the c-axis Josephson plasma resonance (JPR) in La2−xBaxCuO4 (x = 0.115) as a direct probe of superconductivity dynamics following excitation with near-infrared pulses. Starting from the superconducting state, c-axis polarized excitation with a fluence of 100 μJ/cm2 results in an increase of the far-infrared spectral weight by more than an order of magnitude as evidenced by a blueshift of the JPR, interpreted as resulting from nonthermal collapse of the charge order. The photoinduced signal persists well beyond our measurement window of 300 ps and exhibits signatures of spatial inhomogeneity. The electrodynamic response of this metastable state is consistent with enhanced superconducting fluctuations. Our results reveal that La2−xBaxCuO4 is highly sensitive to nonequilibrium excitation over a wide fluence range, providing an unambiguous example of photoinduced modification of order-parameter competition.
The objective of this study was to investigate the effects of applying different amounts of water and nitrogen on yield, fruit quality, water use efficiency （WUE）, irrigation water use efficiency ...（IWUE） and nitrogen use efficiency （NUE） of drip-irrigated greenhouse tomatoes in northwestern China. The plants were irrigated every seven days at various proportions of 20-cm pan evaporation （Ep）. The experiment consisted of three irrigation levels （11, 50% Ep; 12, 75% Ep; and 13, 100% Ep） and three N application levels （N1, 150 kg N ha^-1; N2, 250 kg N ha^-1;and N3, 350 kg N ha^-1）. Tomato yield increased with the amount of applied irrigation water in 12 and then decreased in 13. WUE and IWUE were the highest in Ii. WUE was 16.5% lower in 12 than that in I1, but yield was 26.6% higher in 12 than that in I1. Tomato yield, WUE, and IWUE were significantly higher in N2 than that in N1 and N3. NUIE decreased with increasing N levels but NUE increased with increase the amount of water applied. Increasing both water and N levels increased the foliar net photosynthetic rate. I1 and 12 treatments significantly increased the contents of total soluble solids （TSS）, vitamin C （VC）, lycopene, soluble sugars （SS）, and organic acids （OA） and the sugar：acid ratio in the fruit and decreased the nitrate content. TSS, VC, lycopene, and SS contents were the highest in N2. The harvest index （HI） was the highest in 12N2. 12N2 provided the optimal combination of tomato yield, fruit quality, and WUE. The irrigation and fertilisation regime of 75% Ep and 250 kg N ha^-1 was the best strategy of water and N management for the production of drip-irrigated greenhouse tomato.
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