High Pressure Study Of Low-Dimensional Correlated Materials

Low-dimensional correlated electronic materials have attracted extensive attention in condensed matter physics,material engineering,microelectronics,and other fields due to their unique physical properties and potential practical utility.Exploration and development of more low-dimensional correlated electronic materials and effective control is the leading-edge field.As a clean,effective,and continuous way to tune the physical property of solids,high-pressure can compress the distance between atoms,regulate the interaction between electrons and phonons,and between electrons,thus orderly regulating various physical properties in materials.In this thesis,we explore the physical properties of several low dimensional related electronic materials under high-pressure,and reveal the pressurized physical properties evolution and internal mechanism.The main sections of the researches and results are as follows:1.Charge density waves in two-dimensional material VSe₂ were explored under high-pressure.High-quality VSe₂ single crystals are obtained by the chemical vapor transport method.The X-ray diffraction,energy dispersive X-ray analysis,electrical transport,magnetic,and Raman spectrum results showed the ratio of atoms in obtainedVSe₂ single crystals near-ideal V:Se=1:2 with high crystal quality.Subsequently,we measured the high-pressure electrical transport of the obtained high-quality single crystal,and the charge density wave transition temperature reached the highest 358 K at 14.6 GPa.The pressure-enhanced charge density wave in VSe₂ is confirmed by Raman spectra,and high-pressure X-ray diffraction results show that the charge density wave is enhanced within the original crystal structure.By evaluating the pressure-dependent axial ratio c/a and the trend for transition temperature of charge density wave under pressure,it is found that the pressure enhanced charge density wave in 1T-VSe₂ is closely related to the intensification of the nested vector in the vertical direction of Fermi surface.Our findings provide a new aperture for understanding the internal mechanism of charge density waves,developing candidate materials for room temperature charge density waves,and promoting the application of related microelectronics devices.2.The metallization and superconductivity of two-dimensional materials SnS₂ were studied systematically.SnS₂ single crystals were grown by the chemical vapor transport method.The results of IR reflectance spectra and electrical transport under high pressures show that SnS₂ metalized at around 35 GPa and superconductivity occurs at about 44 GPa.The superconducting transition temperature is enhanced from 2.6 K to 6.2 K between 44～82 GPa.In-situ X-ray diffraction measurements show the stability of the trigonal structure under compression.Interestingly,a Lifshitz transition,which has an important bearing on the metallization and superconductivity,is identified by the first-principles calculations between 35 GPa and 40 GPa.This work provides a unique research platform for exploring the relationship between electronic structure,metallization,and superconductivity under high pressure without crystal structural collapse.3.High-quality HfS₃ quasi-one-dimensional single crystal was grown by chemical vapor transport method,and a superconducting state was observed at 125 GPa by electrical transport under high pressures.The superconducting transition temperature increases gradually from 7.2 K at125 GPa to 11.3 K at 181 GPa,and the trend is not sluggish.We also found that the crystal structure of HfS₃ remains stable below 150 GPa by synchrotron radiation X-ray diffraction under high pressure.This work found a quasi-one-dimensional superconductor with high superconducting transition temperature and provides a candidate material with particularity for possible spin-orbit coupling and electronic structure evolution in quasi-one-dimensional superconductors.