博士生丁俊男同学在国际纳米权威期刊Nano Research上发表论文

博士生丁俊男同学在国际纳米权威期刊Nano Research上发表论文

       近日，课题组博士生丁俊男同学在刘老师的指导下，以第一作者在国际纳米权威期刊《纳米研究》(Nano Research，影响因子9.5)上发表题为“Pressure-Driven Layer-dependent Phase Transitions and Enhanced Interlayer Coupling in PdSe₂ Crystals”(PdSe₂晶体中压力驱动的层依赖相变和层间耦合增强特性)的实验论文。

图：PdSe₂晶体中压力驱动的层依赖相变和层间耦合增强特性

      过渡金属二硫属化物(TMDs)因其独特的电子、光学和机械特性，成为极具潜力的材料，适用于多种技术应用。在TMDs中，二硒化钯(PdSe₂)因其独特的层状结构和稳定性而脱颖而出，具有在柔性电子、光电器件和非线性光学研究中的潜在应用。层状PdSe₂具有正交对称晶体结构和折叠的五边形晶格，在外部应变和压力下会经历一系列结构和物理特性的变化，如相变、铁弹性和各向异性声子。

      压力显著改变原子配置和层间相互作用，从而导致材料的电子和结构特性的变化。最近对范德华(vdW)材料的研究表明，压力可以调控晶体结构，从而改变电子和光学特性，甚至在某些条件下实现超导相。在块体PdSe₂ 中，它在5到9 GPa的高压下从正交相过渡到立方相，这一转变伴随着半导体到金属的转变，在7.2 GPa下出现超导态，转变温度(Tc)为2.4 K。进一步将压力增加到23 GPa可以将Tc提高到13.1 K，这表明高压下块体PdSe₂ 的晶体和电子结构发生了显著调制。然而，几层PdSe₂的晶体结构和物理特性在高压下的演变尚不清楚。

      为了解决这一空白，我们利用金刚石对顶砧(DAC)和拉曼光谱技术，研究了单层(1L)到五层(5L)、少层(FL)和块体PdSe₂的高压拉曼和偏振光谱演变。我们的结果表明，层间呼吸模(BM)的蓝移速率表现出层依赖性，随层数增加而增加。这归因于压力引起的层间间距减少，增强了层间耦合效应，随着厚度增加变得更加明显。此外，压力可以诱导PdSe₂从正交相过渡到立方相，转变压力表现出明显的层依赖性，随层数增加而减小。例如，3L PdSe₂ 晶体的相变压力为17.95 GPa，而块体的相变压力降至3.59 GPa，这突显了层厚度对相变行为的显著影响。此外，我们对不同压力下PdSe₂各向异性变化的研究表明，随着压力的增加，各向同性逐渐接近。本研究强调了厚度在压力诱导的vdW材料结构相变中的关键作用，并提供了一种调控二维材料固有特性的有效工具。

论文链接： https://link.springer.com/article/10.1007/s12274-024-6927-4

Comments:

The paper "Pressure-Driven Layer-dependent Phase Transitions and Enhanced Interlayer Coupling in PdSe₂ Crystals" provides a comprehensive examination of the effects of high pressure on the structural properties of PdSe₂. The authors effectively utilize diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy to delve into the pressure-induced structural evolution of PdSe₂, particularly focusing on its layer-dependent characteristics.

The study is notable for its detailed investigation into how pressure enhances interlayer coupling in PdSe₂, leading to phase transitions from an orthorhombic to a cubic phase. The revelation that PdSe₂ exhibits distinct layer-dependent pressure thresholds during these phase transitions, with a decrease in transition pressure as thickness increases, is particularly insightful. This finding underscores the significant impact of layer thickness on the phase transition behavior of van der Waals materials under high pressure.

Additionally, the results on polarized Raman spectra, which indicate a reduction in material anisotropy with increasing pressure, add a valuable dimension to our understanding of the anisotropic properties of PdSe₂ under varying pressure conditions. These insights contribute significantly to the broader field of van der Waals materials, enhancing our comprehension of their pressure-induced behaviors and potential applications.

Overall, this paper provides crucial insights and advances our understanding of the structural evolution of layer-dependent van der Waals materials under pressure. It is a valuable contribution to the field and opens up new avenues for research into the pressure-induced behaviors of similar materials.