Corrigendum to: “Incompatibility of published ac magnetic susceptibility of a room temperature superconductor with measured raw data” [Matter Radiat. Extremes 7, 048401 (2022)]

(1)The caption of Fig.11 erroneously states“(c)Reproduced with permission from Debessai et al.,Phys.Rev.Lett.102,197002(2009).Copyright 2009 the American Physical Society.”Instead it should state“(c)Reproduced with permission from Debessai et al.,Phys.Rev.B 78,064519(2008).Copyright 2008 the American Physical Society.”

Incompatibility of published ac magnetic susceptibility of a room temperature superconductor with measured raw data

A material termed“carbonaceous sulfur hydride”has recently been reported to be a high-pressure room temperature superconductor[Snider et al.,Nature 586,373(2020)].We have previously pointed out that certain anomalies observed in the published data for the ac magnetic susceptibility of this material would be cleared up once the measured raw data were made available[J.E.Hirsch,arXiv:2110.12854v1(2021)and J.E.Hirsch,Physica C 590,1353964(2021)(temporarily removed)].The measured raw data,as well as numerical values of the data presented in figures in the aforementioned paper by Snider et al.,have recently been posted on the arXiv[R.P.Dias and A.Salamat,arXiv:2111.15017v1(2021)and R.P.Dias and A.Salamat,arXiv:2111.15017v2(2021)].Here,we report the results of our analysis of these raw data and published data and our conclusion that the raw data are incompatible with the published data.Implications of these results for the claim that the material is a room temperature superconductor are discussed.

Sn-based type-VIII single-crystal clathrates with a large figure of merit

Single-crystal samples of type-VIII BasGa16-xCuxSn30 （x = 0, 0.03, 0.06, 0.15） clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5 × 10^19 cm^-3 for all the samples, the carrier mobility, μH, increases to more than twice that of BasGa16Sn30 for all the Cu doping samples, and consequently the electrical conductivity is enhanced distinctly from 1.90×10^4 S/m to 4.40 ×10^4 S/m, with the Cu composition increasing from x = 0 to x = 0.15. The Seebeck coefficient,α, decreases slightly with the increases in Cu composition. The values are about 0.72 W/mK at 300 K and are almost invariant with temperature up to 500 K for the samples with x = 0 and x = 0.03. The lattice thermal conductivity, μL, decreases from 0.59 W/InK for x = 0 to 0.50 W/mK for x = 0.03 at 300 K. The figure of merit for x = 0.03 reaches 1.35 at 540 K.

Interplay between cold densification and malic acid addition (C4H6O5) for the fabrication of near-isotropic MgB2 conductors for magnet application

The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20 K and 25 K as well as at applied magnetic fields up to 19 T.The study includes binary and C4H6O5(malic acid)doped MgB2 tapes before and after CHPD.It is remarkable that the CHPD process not only improved the Jc values,in particular at the higher magnetic fields,but also decreased the anisotropy ratio,Г=JC^///JC^⊥In binary MgB2 tapes,the anisotropy factor F increases with higher aspect ratios,even after applying CHPD.In malic acid(C4H6O5)doped tapes,however,the application of CHPD leads only to small enhancements ofГ,even for higher aspect ratios.This is attributed to the higher carbon content in the MgB2 filaments,which in turn is a consequence of the reduced chemical reaction path in the densified filaments.At all applied field values,it was found that CHPD processed C4H6O5 doped tapes exhibit an almost isotropic behavior.This constitutes an advantage in view of industrial magnet applications using wires with square or slightly rectangular configuration.

Point-contact spectroscopy on antiferromagnetic Kondo semiconductors Ce𝑇T2Al10 (T= Ru and Os)

We have carried out point-contact spectroscopy(PCS)measurements on one family of antiferromagnetic Kondo semiconductor CeT2Al10(T=Ru and Os)with a Neel temperature´TN∼27.5 and 28.5 K,respectively.Their PCS conductance curves both exhibit a characteristic coherent double-peak-structure at temperatures below TN,signaling an AFM gap around the Fermi surface.The temperature dependent AFM gap∆1 follows a Bardeen-Cooper-Schrieffer(BCS)-like mean-field behavior with a moderate gap anisotropy for PCS along different crystal axes.Another asymmetric gap-like feature is observed for both compounds at temperatures far below TN,which is consistent with opening of a new hybridization gap∆h inside the long-range ordered AFM state.Our results suggest a common itinerant nature of the anomalous AFM ordering,constraining theoretical models to explain the AFM origin in CeRu2Al10 and CeOs2Al10.

Common microscopic origin of the phase transitions in Ta_(2)NiS_(5) and the excitonic insulator candidate Ta_(2)NiSe_(5)

The structural phase transition in Ta-NiSes has been envisioned as driven by the formation of an excitonic insulating phase.However,the role of structural and electronic instabilities on crystal symmetry breaking has yet to be disentangled.Meanwhile,the phase transition in its complementary material Ta_(2)NiS_(5)does not show any experimental hints of an excitonic insulating phase.We present a microscopic investigation of the electronic and phononic effects involved in the structural phase transition in Ta_(2)NiSe_(5)and Ta-Niss using extensive first-principles calculations.In both materials the crystal symmetries are broken by phonon instabilities,which in tum lead to changes in the electronic bandstructure also observed in the experiment.A total energy landscape analysis shows no tendency towards a purely electronic instability and we find that a sizeable lattice distortion is needed to open a bandgap.We conclude that an excitonic instability is not needed to explain the phase transition in both Ta_(2)NiSe_(5)and Ta_(2)NiS_(5).

Local and correlated studies of humidity-mediated ferroelectric thin film surface charge dynamics

Electrochemical phenomena in ferroelectrics are of particular interest for catalysis and sensing applications,with recent studies highlighting the combined role of the ferroelectric polarisation,applied surface voltage and overall switching history.Here,we present a systematic Kelvin probe microscopy study of the effect of relative humidity and polarisation switching history on the surface charge dissipation in ferroelectric Pb(Zr_(0.2)Ti_(0.8))O_(3)thin films.We analyse the interaction of surface charges with ferroelectric domains through the framework of physically constrained unsupervised machine learning matrix factorisation,Dictionary Learning,and reveal a complex interplay of voltage-mediated physical processes underlying the observed signal decays.Additional insight into the observed behaviours is given by a Fitzhugh–Nagumo reaction–diffusion model,highlighting the lateral spread and charge passivation process contributors within the Dictionary Learning analysis.

Annealing-induced long-range charge density wave order in magnetic kagome FeGe:Fluctuations and disordered structure

Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which magnetism and CDW are intertwined to form an emergent quantum ground state. However, the CDW is only short-ranged and the structural modulation originating from it has yet to be determined experimentally. Here we realize a long-range CDW order by post-annealing process,and resolve the structure model through single crystal X-ray diffraction. Occupational disorder of Ge resulting from short-range CDW correlations above T_(CDW) is identified from structure refinements. The partial dimerization of Ge along the c axis is unveiled to be the dominant distortion for the CDW. Occupational disorder of Ge is also proved to exist in the CDW phase due to the random selection of partially dimerized Ge sites. Our work provides useful insights for understanding the unconventional nature of the CDW in FeGe.

Smart machine learning or discovering meaningful physical and chemical contributions through dimensional stacking

Despite remarkable advances in characterization techniques of functional materials yielding an ever growing amount of data,the interplay between the physical and chemical phenomena underpinning materials’functionalities is still often poorly understood.Dimensional reduction techniques have been used to tackle the challenge of understanding materials’behavior,leveraging the very large amount of data available.Here,we present a method for applying physical and chemical constraints to dimensional reduction analysis,through dimensional stacking.Compared to traditional,uncorrelated techniques,this approach enables a direct and simultaneous assessment of behaviors across all measurement parameters,through stacking of data along specific dimensions as required by physical or chemical correlations.The proposed method is applied to the nanoscale electromechanical relaxation response in(1−x)PMN-xPT solid solutions,enabling a direct comparison of electric field-and chemical composition-dependent contributors.A poling-like,and a relaxation-like behavior with a domain glass state are identified,and their evolution is tracked across the phase diagram.The proposed dimensional stacking technique,guided by the knowledge of the underlying physics of correlated systems,is valid for the analysis of any multidimensional dataset,opening a spectrum of possibilities for multidisciplinary use.

La_(4)TX(T=Ru,Rh,Ir;X=Al,In):一个具有可调节反对称自旋轨道耦合强度的新型非中心对称超导体系

本文报道了非中心对称化合物家族La_(4)TX(T=Ru,Rh,Ir;X=Al In)中的超导电性.该系列超导体具有立方晶体结构,空间群为F 43m La_(4)RuAl,La_(4)RhAl,La_(4)IrAl,La_(4)RuIn和La_(4)IrIn的超导转变温度在0.61–3.35 K之间,而La_(4)RuIn尚未被成功制备.La_(4)RuAl和La_(4)RhAl的低温比热可由无超导能隙节点的s波超导描述,而自旋-轨道耦合强度较大的La_(4)IrAl则可能存在能隙节点.这些超导体的上临界磁场都可由Werthamer-Helfand-Hohenberg模型描述,且上临界场Hc2(0)远低于泡利极限,说明轨道效应在库伯对拆对机制中占据主导.密度泛函理论计算表明,对于该超导家族的不同化合物,其反对称自旋-轨道耦合导致的能带劈裂存在明显区别,有助于进一步探究超导配对态与反对称自旋-轨道耦合强度之间的联系.