标题： 压强下的异常电荷密度波和费米面重构在BaFe2Al9中 显示英文标题

标题： Anomalous Charge Density Wave and Fermi Surface Reconstruction in Pressurized BaFe2Al9

摘要： 一种金属间化合物BaFe2Al9表现出与电荷密度波（CDW）转变相关的异常物理性质。 与通常表现出细微结构畸变或晶格调制的常规CDW材料不同，BaFe2Al9经历了一种一级相变，其中晶格应变在CDW态的形成中起着关键作用。 为了进一步探索这种独特行为，我们进行了高压研究，考察了电输运、磁性和结构特性，以更深入地了解CDW机制的内在原因。 在常压下，电阻率和磁化测量确认了CDW转变的存在。 施加压力后，CDW转变温度（TCDW）向更高值移动，在约3.2 GPa时达到约300 K，并且电阻率增加，表明压力调节了载流子浓度。 此外，最初尖锐的一级转变变得更为渐进，电阻率温度导数的分析表明，在压力下发生了从一级到二级类似行为的转变。 高压磁化测量与电输运数据一致，显示出随着压力增加，TCDW增强。 剩余电阻率随压力增加而增加，而在2 GPa以上，费米液体系数A减小，这指向可能的费米面重构。 室温下的高压同步辐射粉末X射线衍射（XRD）测量显示在约3.8 GPa处出现晶格异常，宏观应变表现出明显的趋势变化，进一步支持了压力诱导的结构响应的存在。 这些发现为BaFe2Al9中CDW形成的本质提供了有价值的见解，并强调了晶格应变和外部压力在其电子基态调控中的关键作用。 显示英文摘要

摘要： The intermetallic compound BaFe2Al9 exhibits unusual physical properties associated with a charge density wave (CDW) transition. Unlike conventional CDW materials, which typically display subtle structural distortions or lattice modulations, BaFe2Al9 undergoes a first-order phase transition in which lattice strain plays a crucial role in the formation of the CDW state. To further explore this unique behavior, we conducted high-pressure studies, examining the electrical transport, magnetic, and structural properties to gain deeper insight into the underlying CDW mechanism. At ambient pressure, electrical resistivity and magnetization measurements confirm the presence of a CDW transition. Upon applying pressure, the CDW transition temperature (TCDW) shifts to higher values, reaching approximately 300 K near 3.2 GPa, and the electrical resistivity increases, suggesting that pressure modulates the charge carrier concentration. Furthermore, the initially sharp first-order transition becomes more gradual, and analysis of the temperature derivative of resistivity indicates a crossover from first-order to second-order like behavior under pressure. High-pressure magnetization measurements are consistent with the electrical transport data, showing an enhancement of TCDW with increasing pressure. The residual resistivity increases with pressure, while the Fermi liquid coefficient A decreases above 2 GPa, pointing to a possible Fermi surface reconstruction. High-pressure synchrotron powder X-ray diffraction (XRD) measurements at room temperature reveal a lattice anomaly near 3.8 GPa, marked by a distinct trend change in macrostrain, further supporting the existence of a pressure induced structural response. These findings provide valuable insight into the nature of CDW formation in BaFe2Al9 and highlight the critical role of lattice strain and external pressure in tuning its electronic ground state.