【作者】 张靖；

【导师】 朱增伟；

【作者基本信息】 华中科技大学 ， 物理学， 2023， 硕士

【摘要】 电荷密度波（CDW）起因于电子-声子的相互作用,是凝聚态物理中一种重要的物理现象。它与超导、Mott绝缘相等凝聚态结构互相关联影响,因此对电荷密度波的研究将有助于对材料中各种物理性质进行更加有效的精准调控。常用的调控手段通常依赖于掺杂、压力、厚度的控制,而基于非平衡变化,使用变温速率来控制的动力学手段则缺乏研究。本论文中,我们首先设计并制作了可以提供超快变温速率的快速差示扫描量热装置,并将其安装于16T牛津超导磁体系统中;使用快速差示扫描量热装置对准二维CDW材料IrTe₂和1T-TaS₂进行了热动力学的分析。论文将分为以下五个章节:第一章首先给出了电荷密度波的基本物理概念、以及其在准二维电子体系中的研究现状和进展,并着重讲述了电荷密度波的各种调控方式。此外,还介绍了热分析技术的发展历史与其广泛的适用领域。第二章,我们设计并搭建了快速的差示扫描量热装置,成功将其应用在低温强磁场环境,并完成了系统的调试。第三章,使用快速差示扫描量热装置测量了单晶IrTe₂在不同变温速率下的量热分析,并在CDW与高温金属相的共存温区发现了速率依赖的类玻璃化转变行为。此转变对变温速率的依赖关系相反于常规的玻璃化转变,我们将其归结于体系中有序度随温度分布的不同导致的反常过冷态。第四章,在不同磁场下测量了单晶1T-TaS₂的量热曲线,验证了1T-TaS₂中的几个CDW转变,并且发现CDW对磁场或变温速率的变化并不敏感。这说明1T-TaS₂的磁结构与费米面在高达16T的磁场下与500K/s的变温速率下仍具备很强的稳定性。更多还原

【Abstract】 Charge density wave comes from the electron-phonon interaction and it’s an important physical phenomenon in condensed matter physics.It is interrelated with superconductivity,Mott insulation and other condensed matter structures,so the studies of charge density wave will help to control various physical properties in materials more effectively and precisely.The commonly used means of control usually rely on the change of doping,pressure,and thickness,while kinetic means based on non-equilibrium transitions,which are controlled using variable temperature rates,are lacking in research.In this thesis,we first designed and fabricated a fast differential scanning calorimetry device,which can provide ultra-fast temperature rates,and installed it in a 16T Oxford superconducting magnet system;we used the fast differential scanning calorimetry device to analyze the thermal dynamics of quasi-two dimensional CDW materials IrTe₂and 1T-TaS₂.This thesis will be divided into five chapters as follows:Chapter 1 first gives the basic physical concepts of charge density waves,as well as the current status and progress of their studies in the quasi-two-dimensional electronic system,and focuses on the various ways of manipulating charge density waves.In addition,we present the history of the development of thermal analysis techniques and their wide range of applications.In Chapter 2,we designed and built a fast differential scanning calorimetry device,and successfully applied it to low-temperature and high magnetic field and completed the test of the system.In Chapter 3,we finished the calorimetric analysis of single-crystal IrTe₂ at different rates of temperature with the fast differential scanning calorimetry device,and found a rate-dependent glass transition-like behavior in the temperature region of coexistence of CDW with the high-temperature metallic phase.The dependence of this transition on the rates of temperature is in contrast to the conventional glass transition and we attribute it to a supercooling state caused by the difference in the distribution of the Orderliness in the system with temperature.In Chapter 4,we measured the calorimetric curves of single-crystal 1T-TaS₂ at different magnetic fields and verified several CDW transitions in of 1T-TaS₂ and found that the CDW is not sensitive to the variation of magnetic field or the rate of temperature.This indicates that the magnetic structure of 1T-TaS₂ with Fermi surface possesses strong stability at magnetic fields up to 16 T and at variable temperature rates of 500 K/s.更多还原