查看更多>>摘要：Hydride superconductors continue to fascinate the communities of condensed matter physics and material scientists because they host the promising near room-temperature superconductivity.Current research has concentrated on the new hydride superconductors with the enhancement of the superconducting transition temperature(Tc).The multiple extreme conditions(high pressure/temperature and magnetic field)will introduce new insights into hydride superconductors.The study of transport properties under very high magnetic fields facilitates the understanding of superconductivity in conventional hydride superconductors.In the present work,we report experimental evidence of an unusual metal state in a newly synthesized cubic A15-type La4H23 that exhibits superconductivity with a Tc reaching 105 K at 118 GPa.A large negative magnetoresistance is observed in strong pulsed magnetic fields in the non-superconducting state of this compound below 40 K.Moreover,we construct the full magnetic phase diagram of La4H23 up to 68 T at high pressure.The present work reveals anomalous electronic structural properties of Al5-La4H23 under high magnetic fields,and therefore has great importance with regard to advancing the understanding of quantum transport behaviors in hydride superconductors.
查看更多>>摘要：The quantum Griffiths singularity(QGS)is a phenomenon driven by quenched disorders that break conventional scaling invariance and result in a divergent dynamic critical exponent during quantum phase transitions(QPT).While this phenomenon has been well-documented in low-dimensional conventional superconductors and in three-dimensional(3D)magnetic metal systems,its presence in 3D superconducting systems and in unconventional high-temperature superconductors(high-Tc SCs)remains unclear.In this study,we report the observation of robust QGS in the superconductor-metal transition(SMT)of both quasi-2D and 3D anisotropic unconventional high-Tc superconductor CaFe1-xNixAsF(x＜5％)bulk single crystals,where the QGS states persist to up to 5.3 K.A comprehensive quantum phase diagram is established that delineates the 3D anisotropic QGS of SMT induced by perpendicular and parallel magnetic fields.Our findings reveal the universality of QGS in 3D superconducting systems and unconventional high-Tc SCs,thereby substantially expanding the range of applicability of QGS.
查看更多>>摘要：Crystalline solids exhibiting inherently low lattice thermal conductivity(KL)are of great importance in applications such as thermoelectrics and thermal barrier coatings.However,KL cannot be arbitrarily low and is limited by the minimum thermal conductivity related to phonon dispersions.In this work,we report the liquid-like thermal transport in a well-ordered crystalline CsAg5Te3,which exhibits an extremely low KL value of～0.18 Wm-1K-1.On the basis of first-principles calculations and inelastic neutron scattering measurements,we find that there are lots of low-lying optical phonon modes at～3.1 meV hosting the avoided-crossing behavior with acoustic phonons.These strongly localized modes are accompanied by weakly bound rattling Ag atoms with thermally induced large amplitudes of vibrations.Using the two-channel model,we demonstrate that coupling of the particle-like phonon modes and the heat-carrying wave-like phonons is essential for understanding the low κL,which is heavily deviated from the 1/T temperature dependence of the standard Peierls theory.In addition,our analysis indicates that the soft structural framework with liquid-like motions of the fluctuating Ag atoms is the underlying cause that leads to the suppression of the heat conduction in CsAg5Te3.These factors synergistically account for the ultralowκL value.Our results demonstrate that the liquid-like heat transfer could indeed exist in a well-ordered crystal.
查看更多>>摘要：The Mott-Ioffe-Regel limit sets the lower bound of the carrier mean free path for coherent quasiparticle transport.Metallicity beyond this limit is of great interest because it is often closely related to quantum criticality and unconventional superconductivity.Progress along this direction mainly focuses on the strange-metal behaviors originating from the evolution of the quasiparticle scattering rate,such as linear-in-temperature resistivity,while the quasiparticle coherence phenomena in this regime are much less explored due to the short mean free path at the diffusive bound.Here we report the observation of quantum oscillations from Landau quantization near the Mott-Ioffe-Regel limit in CaAs3.Despite the insulator-like temperature dependence of resistivity,CaAs3 presents giant magnetoresistance and prominent Shubnikov-de Haas oscillations from Fermi surfaces,indicating highly coherent band transport.In contrast,quantum oscillation is absent in the magnetic torque.The quasiparticle effective mass increases systematically with magnetic fields,manifesting a much larger value than what is expected based on magneto-infrared spectroscopy.This suggests a strong many-body renormalization effect near the Fermi surface.We find that these unconventional behaviors may be explained by the interplay between the mobility edge and the van Hove singularity,which results in the formation of coherent cyclotron orbits emerging at the diffusive bound.Our results call for further study on the electron correlation effect of the van Hove singularity.
查看更多>>摘要：Because of the lack of translational symmetry,calculating the energy spectrum of an incommensurate system has always been a theoretical challenge.Here,we propose a natural approach to generalize energy band theory to incommensurate systems without reliance on the commensurate approximation,thus providing a comprehensive energy spectrum theory of incommensurate systems.Except for a truncation-dependent weighting factor,the formulae of this theory are formally almost identical to that of Bloch electrons,making it particularly suitable for complex incommensurate structures.To illustrate the application of this theory,we give three typical examples:one-dimensional bichromatic and trichromatic incommensurate potential models,as well as a moiré quasicrystal.Our theory establishes a fundamental framework for understanding incommensurate systems.
查看更多>>摘要：Sensors are of fundamental importance and widely used in modern society,such as in industry and environmental monitoring,biomedical sample ingredient analysis and wireless networks.Although numerous sensors have been developed,there is a continuous demand for sensors with increased sensitivity,to detect signals that were previously undetectable.Recently,non-Hermitian degeneracies,also known as exceptional points(EPs),have attracted attention as a way of improving the responsiveness of sensors.In contrast to previous investigations,here we present a new approach to achieving ultra-sensitivity by reconstructing exceptional systems.In the reconstruction process,some eigenstates near the previous EPs are utilized,and non-reciprocal long-range couplings are introduced.The sensitivities of our reconstructed systems have improved by several orders of magnitude compared to those based on EPs.Furthermore,we design and fabricate corresponding integrated circuit sensors to demonstrate the scheme.Our work paves the way for the development of highly sensitive sensors,which have a wide range of applications in various fields.
查看更多>>摘要：Lipid droplets(LDs)are the major sites of lipid and energy homeostasis.However,few LD biogenesis proteins have been identified.Using model microalga Chlamydomonas,we show that ABHD1,anα/β-hydrolase domain-containing protein,is localized to the LD surface and stimulates LD formation through two actions:one enzymatic and one structural.The knockout mutants contained similar amounts of triacylglycerols(TAG)but their LDs showed a higher content of lyso-derivatives of betaine lipid diacylglyceryl-N,N,N-trimethylhomoserine(DGTS).Over-expression of ABHD1 increased LD abundance and boosted TAG content.Purified recombinant ABHD 1 hydrolyzed lyso-DGTS,producing a free fatty acid and a glyceryltrimethylhomoserine.In vitro droplet-embedded vesicles showed that ABHD1 promoted LD emergence.Taken together,these results identify ABHD 1 as a new player in LD formation by its lipase activity on lyso-DGTS and by its distinct biophysical property.This study further suggests that lipases targeted to LDs and able to act on their polar lipid coat may be interesting tools to promote LD assembly in eukaryotic cells.
查看更多>>摘要：Although adeno-to-squamous transition(AST)has been observed in association with resistance to epidermal growth factor receptor(EGFR)tyrosine kinase inhibitor(TKI)in clinic,its causality,molecular mechanism and overcoming strategies remain largely unclear.We here demonstrate that squamous transition occurs concomitantly with TKI resistance in PC9-derived xenograft tumors.Perturbation of squamous transition via DNp63 overexpression or knockdown leads to significant changes in TKI responses,indicative of a direct causal link between squamous transition and TKI resistance.Integrative RNA-seq,ATAC-seq analyses and functional studies reveal that FOXA1 plays an important role in maintaining adenomatous lineage and contributes to TKI sensitivity.FOXM1 overexpression together with FOXA1 knockout fully recapitulates squamous transition and TKI resistance in both PC9 xenografts and patient-derived xenograft(PDX)models.Importantly,pharmacological inhibition of RAPGEF3 combined with EGFR TKI efficiently overcomes TKI resistance,especially in RAPGEF3high PDXs.Our findings provide novel mechanistic insights into squamous transition and therapeutic strategy to overcome EGFR TKI resistance in lung cancer.
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