查看更多>>摘要：As a fundamental theory of structural transformations,the Zener ordering of interstitials in a body-centered cubic host lattice,which was established more than half a century ago,has been challenged by recent first-principles investigations.In this Letter,we rigorously prove the existence of Zener ordering via Monte Carlo simulations with complete interstitial interactions and demonstrate the critical role of long-range indirect strain-induced interactions in stabilizing Zener ordering.These insights improve our understanding of the self-induced collective ordering of point defects in a host lattice and elucidate the fundamental physics of order-disorder phase transitions in alloys.
查看更多>>摘要：The long sought cubic gauche polymeric nitrogen(cg-N)consisting of N-N single bonds has been synthesized by one pot route using sodium azide as a precursor at ambient conditions.The recrystallization process was designed to expose crystal faces with low activation energy that facilitates initiating the polymeric reaction at ambient conditions.The azide was considered as a precursor due to the low energy barrier in transforming double bonded N=N to single bonded cg-N.Raman spectrum measurements detected the emerging vibron peaks at 635 cm-1 for the polymerized sodium azide samples,demonstrating the formation of cg-N with N-N single bonds.Different from traditional high-pressure technique and recently developed plasma enhanced chemical vapor deposition method,the route achieves the quantitative synthesis of cg-N at ambient conditions.The one pot synthesis of cg-N offers potential for further scaling up production as well as practical applications of polymeric nitrogen based materials as high energy density materials.
查看更多>>摘要：We investigate coupled electron and phonon transport in NbX2 with X=Ge,Si,where experimental evidence of strong electron-phonon coupling and hydrodynamic transport has been reported.Based on first-principles density functional theory calculations,we measured the thermal and electrical transport properties of the com-pounds.We found that phonon-electron scattering strongly affects phonon thermal conductivity(κph)and leads to a weak temperature dependence of κph instead of a normal inverse temperature dependence when anharmonic three-phonon scattering dominates.In addition,κph contributes to a quarter of the total thermal conductivity,which differs from typical metals in which the total thermal conductivity is predominantly derived from electrons.In contrast to previous numerical research,our electrical resistivity results agree well with the experimental measurements.The anisotropic properties of the transport coefficients are attributed to the electron-phonon dispersion relation.In addition,we found a negligible effect of electron-phonon drag on the transport properties,contrary to the expectation from a strongly coupled electron-phonon fluid.
查看更多>>摘要：In this study,Kagome superconductors,i.e.,CsV3Sb5 single crystals and its Ta-doped variant,Cs(V0.86Ta0.14)3Sb5,were studied in detail via specific heat measurements.Results revealed that the charge density wave(CDW)was suppressed and the superconducting transition temperature(Tc)considerably increased from 2.8 to 4.6 K upon Ta doping.The electronic specific heat of CsV3Sb5 was fitted with a model comprising an s-wave gap and a highly anisotropic extended s-wave gap,where 2Δ/kBTc was smaller than the weak coupling limit of 3.5.Cs(V0.86Ta0.14)3Sb5 exhibited two isotropic s-wave gaps and yielded a larger gap of 2Δ/kBTc=5.04,indicating a significant enhancement in superconducting coupling.This evolution was attributed to the increased density of states near the Fermi level released by CDW gap suppression.These findings demonstrated that Ta doping enhanced superconducting coupling and variation of gap structure in CsV3Sb5.
查看更多>>摘要：This topical review article reports rapid progress on the generalization and application of entanglement in non-Hermitian free-fermion quantum systems.We begin by examining the realization of non-Hermitian quantum systems through the Lindblad master equation,alongside a review of typical non-Hermitian free-fermion systems that exhibit unique features.A pedagogical discussion is provided on the relationship between entanglement quantities and the correlation matrix in Hermitian systems.Building on this foundation,we focus on how entan-glement concepts are extended to non-Hermitian systems from their Hermitian free-fermion counterparts,with a review of the general properties that emerge.Finally,we highlight various concrete studies,demonstrating that entanglement entropy remains a powerful diagnostic tool for characterizing non-Hermitian physics.The entan-glement spectrum also reflects the topological characteristics of non-Hermitian topological systems,while unique non-Hermitian entanglement behaviors are also discussed.The review is concluded with several future directions.Through this review,we hope to provide a useful guide for researchers who are interested in entanglement in non-Hermitian quantum systems.
查看更多>>摘要：V-based kagome superconductors AV3Sb5(A=K,Rb,and Cs)host a charge density wave(CDW)and a topological nontrivial band structure,thereby providing a great platform to study the interplay of supercon-ductivity(SC),CDW,frustration,and topology.Here,we report ultralow-temperature thermal conductivity measurements of CsV3Sb5 and Ta-doped Cs(V0.86Ta0.14)3Sb5 and scanning tunneling microscopy(STM)mea-surements of CsV3Sb5.The finite residual linear term of thermal conductivity at zero magnetic field suggests the existence of a residual density of states(DOS)in the superconducting state of CsV3Sb5.This is supported by the observation of non-zero conductance at zero bias in STM spectrum at an electronic temperature of 90 mK.However,in Cs(V0.86Ta0.14)3Sb5,which does not have CDW order,there is no evidence for the residual DOS.These results show the importance of CDW order for the residual DOS,and that a nodal s-wave gap or residual Fermi arc may be the origin of the residual DOS in such an unusual multiband kagome superconductor,CsV3Sb5.
查看更多>>摘要：Strongly correlated electrons at the verge of quantum criticality give rise to unconventional phases of matter and behaviors,with the discovery of new quantum-critical materials driving synergistic experimental and theo-retical advances.In this paper,we report the structural and physical properties of a new quaternary Ce-based heavy fermion compound,Ce2NiAl6Si5,which was synthesized via the self-flux method.This compound forms a layered tetragonal structure(space group P4/nmm)with square nets of Ce atoms separated by Si-Al or Ni-Si-Ge layers.Specific heat measurements show a low-temperature Sommerfeld coefficient of 1.4 J/mol-Ce·K2 with re-duced entropy,indicative of significant Kondo interactions.Below 0.6 K,an increase in resistivity and a deviation in magnetic susceptibility suggest the appearance of magnetic ordering or the development of dynamic magnetic correlations,which is further supported by a bulge in the specific heat around 0.4 K.The findings of this study suggest that Ce2NiAl6Si5 is a layered heavy fermion metal naturally located near a spin-density-wave quantum critical point.
查看更多>>摘要：Results of combined thermal and electrical transport measurements through the magnetic field-induced quan-tum critical point(QCP)in the heavy-fermion compound YbRh2Si2 were revisited to explore the relationship between the strange-metal behavior observed in electrical and electronic thermal resistivities and the violation of the Wiedemann-Franz(WF)law in the zero-temperature limit.A new type of inelastic scattering center for the charge and heat carriers was detected,attributed to small-to-large Fermi surface fluctuations operating near the Kondo-destroying QCP.These fermionic quantum critical fluctuations are considered the primary driver of the strange-metal behavior and the violation of the WF law.
查看更多>>摘要：Hydrogen-based compounds have attracted significant attention in recent years due to the discovery of conven-tional superconductivity with high critical temperature under high pressure,rekindling hopes for finding room-temperature superconductors.In this study,we investigated the vibrational and superconducting properties of H3Se in the Im3m phase under pressures of 50-200 GPa.Our approach combines the stochastic self-consistent harmonic approximation and first-principles calculations to account for the quantum and anharmonic effects of ions.According to the results,these effects significantly modify the crystal structure,increasing the inner pres-sure by approximately 8 GPa compared to situations in which they are ignored.The phonon spectra suggest that when these effects are considered,the crystal stabilizes at pressures as low as approximately 61 GPa,which is significantly lower than the previously predicted value of over 100 GPa.Our calculations also highlight the critical role of quantum and anharmonic effects on the electron-phonon coupling properties.Neglecting these factors can result in a significant overestimation of the superconducting critical temperature(Tc)by approximately 4K(200 GPa)to 25 K(125 GPa).With anharmonic phonons,the Tc calculated from the Migdal-Eliashberg equations reaches 200 K(μ*=0.1,λ=4.1)as the pressure decreases to 64 GPa,indicating that the crystal is a rare high-Tc superconductor at moderate pressures.
查看更多>>摘要：The discovery of high-temperature superconductivity in La3Ni2O7 and La4Ni3O10 under pressure has garnered extensive attention.Herein,we report systematic investigations on the structure,magnetism,and electrical resistance evolutions of Pr4Ni3O10-δ polycrystalline samples under various pressures.Pr4Ni3O10-δ exhibits density wave transitions on Ni and Pr sublattices at approximately 157.6 and 4.3 K,respectively.The density wave can be progressively suppressed by pressure.A structural transformation from the monoclinic P21/a space group to the tetragonalI4/mmmoccurs around 20 GPa.An apparent drop in resistance with an evident magnetic field dependence is observed at pressures above 20 GPa,indicating the emergence of superconductivity.The discovery of superconductivity in Pr4Ni3O10-δ broadens the family of nickelate superconductors.Pr4Ni3O10-δ provides a new platform for investigation of the mechanisms of superconductivity in the Ruddlesden-Popper phases of nickelates.
万方数据
维普