Quantum phase transitions in CePdAl probed by ultrasonic and thermoelectric measurements

CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressure- or field-tuned, extended quantum critical phase at zero temperature. Identifying characteristic signatures of the emerging quantum critical phase, which are expected to be distinct from those near a quantum critical point, remains challenging. In this work, by performing ultrasonic and thermoelectric measurements down to very low temperatures in a ³He-⁴He dilution refrigerator in the presence of magnetic field, we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase, including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.     

Switching plasticity in compensated ferrimagnetic multilayers for neuromorphic computing

Current-induced multilevel magnetization switching in ferrimagnetic spintronic devices is highly pursued for the application in neuromorphic computing. In this work, we demonstrate the switching plasticity in Co/Gd ferrimagnetic multilayers where the binary states magnetization switching induced by spin-orbit toque can be tuned into a multistate one as decreasing the domain nucleation barrier. Therefore, the switching plasticity can be tuned by the perpendicular magnetic anisotropy of the multilayers and the in-plane magnetic field. Moreover, we used the switching plasticity of Co/Gd multilayers for demonstrating spike timing-dependent plasticity and sigmoid-like activation behavior. This work gives useful guidance to design multilevel spintronic devices which could be applied in high-performance neuromorphic computing.     

A single dual-mode gas sensor for early safety warning of Li-ion batteries: Micro-scale Li dendrite and electrolyte leakage

Li dendrites and electrolyte leakage are common causes of Li-ion battery failure. H₂, generated by Li dendrites, and electrolyte vapors have been regarded as gas markers of the early safety warning of Li-ion batteries. SnO₂-based gas sensors, widely used for a variety of applications, are promising for the early safety detection of Li-ion batteries, which are necessary and urgently required for the development of Li-ion battery systems. However, the traditional SnO₂ sensor, with a single signal, cannot demonstrate intelligent multi-gas recognition. Here, a single dual-mode (direct and alternating current modes) SnO₂ sensor demonstrates clear discrimination of electrolyte vapors and H₂, released in different states of Li-ion batteries, together with principal component analysis (PCA) analysis. This work provides insight into the intelligent technology of single gas sensors.     

Universal order-parameter and quantum phase transition for two-dimensional q-state quantum Potts model

We investigate quantum phase transitions for q-state quantum Potts models (q=2,3,4) on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with a simplified updating scheme. We extend the universal order parameter to a two-dimensional lattice system, which allows us to explore quantum phase transitions with symmetry-broken order for any translation-invariant quantum lattice system of the symmetry group G. The universal order parameter is zero in the symmetric phase, and it ranges from zero to unity in the symmetry-broken phase. The ground-state fidelity per lattice site is computed, and a pinch point is identified on the fidelity surface near the critical point. The results offer another example highlighting the connection between (i) critical points for a quantum many-body system undergoing a quantum phase-transition and (ii) pinch points on a fidelity surface. In addition, we discuss three quantum coherence measures: the quantum Jensen-Shannon divergence, the relative entropy of coherence, and the l₁ norm of coherence, which are singular at the critical point, thereby identifying quantum phase transitions.     

任意维欧氏空间的长程势多极展开

给出了在任意维欧氏空间中一个一般的长程相互作用势的多极展开结果,并推导得到了单极子和偶极子两两之间的相互作用力公式.     

Zn,Cr∶LiNbO3单晶的坩埚下降法生长及其荧光光谱

通过选择合适的化学原料（Li2O∶48.6mol%, Nb2O5∶51.4mol%）、控制生长速度（<3 mm/h）及固液界面的温度梯度（20~40℃/cm）与温场，用坩埚下降法成功地生长出了Zn、Cr双掺杂初始浓度分别为3 mol%、0.1 mol%,以及6 mol%、0.1 mol%的大尺寸铌酸锂晶体.生长的晶体无宏观缺陷,在He-Ne激光的照射下，无散射中心.测定了晶体的宽带荧光光谱（700~1200nm）及R带（710~740nm）的精细变温光谱.这些R带的光谱线由Cr离子所取代的Li(Cr3+Li)与Nb(Cr3+Nb)的发光中心以及声子辅助吸收所致.     

偏振滤波白天抑制天光背景作用分析

由于天文观测领域大部分自适应光学系统只能在夜晚工作,提出了采用偏振滤波技术抑制天光背景的办法以达到白天探测微弱星体目标的目的。介绍了偏振滤波的原理并估算了抑制天光背景的效果,通过观测角度关系得到了偏振方位角的计算公式,并在丽江观测站1.8m望远镜自适应光学系统平台上进行实验,给出了消像旋模型。实验结果表明,偏振滤波技术能有效抑制天光背景,提高星体目标探测能力,一定程度上提高了自适应光学系统在白天探测弱小星体目标的可能性。     

基于高光谱成像技术的滩羊肉新鲜度快速检测研究

滩羊肉的新鲜度是其品质安全的一个重要衡量指标,也是肉品品质安全控制的关键环节。挥发性盐基氮（TVB-N）是表征肉品腐败过程主要的化学信息,能有效地评价出滩羊肉的新鲜度。然而,TVB-N的传统检测过程繁琐且人为影响因素大,检测结果缺乏客观性和一致性,不能满足当今肉品检测过程无损、快速、高效的需求。高光谱成像技术符合现代检测技术向多源信息融合方向发展的需求,已在食品安全领域得到广泛应用。利用可见/近红外高光谱成像技术（400~1 000 nm）结合动力学和化学计量学方法以及计算机编程技术,将同时实现滩羊肉贮存期内（15 ℃环境）TVB-N 浓度的快速检测和贮藏期的预测。研究中提取每个样品感兴趣区域的平均光谱数据,选用蒙特卡洛算法剔除异常样本。采用X-Y共生距离（SPXY）法划分为校正集和预测集,分别选用多元散射校正（multiplicative scatter correction, MSC）、卷积平滑（savitzky-golay, SG）、标准变量变换（standard normalized variate, SNV）、归一化（normalization）、基线校准（baseline）五种方法对原始光谱数据进行预处理,优选出最佳预处理方法。采用竞争性自适应重加权法（campetitive adaptive reweighted sampling, CARS）和连续投影算法（successive projections algorithm, SPA）分别提取了21个和6个特征波长。为优化模型并提高其模型精度,采用SPA算法对 CARS 所选特征波长进行二次提取,优选出14个特征波长。基于所提取的特征波长建立TVB-N浓度的PLSR模型,优选出 SNV-CARS-SPA-PLSR 模型具有较高的预测能力（R2_c=0.88,RMSEC=2.51, R2_p=0.65, RMSEP=2.11）。同时,建立了滩羊肉TVB-N变化与贮藏时间的动力学模型,并将优化后的光谱模型和动力学反应模型相结合建立了滩羊肉光谱吸光度值与贮藏时间的高光谱动力学模型,实现对贮藏时间的预测,并通过 PLS-DA判别模型对滩羊肉贮藏时间进行判别分析（校正集判别准确率为100%,预测集为97%）。研究表明,利用可见/近红外高光谱成像技术结合动力学和化学计量学方法以及计算机编程技术,可以有效地实现滩羊肉品质智能监控与质量安全快速无损分析,为开发实时在线检测装备提供理论参考。     

Nd2Fe14B/α-Fe双泪永磁合金快淬带的织构与形貌

利用X射线衍射仪和扫描探针显微镜研究了NeFeB系双相永磁合金快淬带的织构与形貌.结果表明,合金快淬带自由面存在择优取向.与三元NdFeB合金相比,复合添加Dy和Ga具有增加合金快淬带织构和细化组织形貌的作用. 关键词：     

First-principles analysis of phonon thermal transport properties of two-dimensional WS_2/WSe_2 heterostructures

The van der Waals(vdW)heterostructures of bilayer transition metal dichalcogenide obtained by vertically stacking have drawn increasing attention for their enormous potential applications in semiconductors and insulators.Here,by using the first-principles calculations and the phonon Boltzmann transport equation(BTE),we studied the phonon transport properties of WS2/WSe2 bilayer heterostructures(WS2/WSe2-BHs).The lattice thermal conductivity of the ideal WS2/WSe2-BHs crystals at room temperature(RT)was 62.98 W/mK,which was clearly lower than the average lattice thermal conductivity of WS2 and WSe2 single layers.Another interesting finding is that the optical branches below 4.73 THz and acoustic branches have powerful coupling,mainly dominating the lattice thermal conductivity.Further,we also noticed that the phonon mean free path(MFP)of the WS2/WSe2-BHs(233 nm)was remarkably attenuated by the free-standing monolayer WS2(526 nm)and WSe2(1720 nm),leading to a small significant size effect of the WS2/WSe2-BHs.Our results systematically demonstrate the low optical and acoustic phonon modes-dominated phonon thermal transport in heterostructures and give a few important guidelines for the synthesis of van der Waals heterostructures with excellent phonon transport properties.