Research On Two-dimensional Tellurene And GeS Under High Pressure

Due to their unique structure and properties,two-dimensional materials have attracted extensive attention and become a research hotspot in condensed matter physics and materials science.There are a variety of 2D materials,including insulators,semiconductors,metals and even superconductors.Most kinds of 2D materials have different physical and chemical properties,so 2D material presents great application potential.Among them,the two-dimensional novel phenomena and laws in the field of superconducting materials caused the heat of the research,the present study shows that the dimensional variation on the influence of superconductivity is profound and great,as a result,the superconducting properties of two-dimensional materials for research not only helps to find new high temperature superconductors,also deepen mining and understanding of the superconducting mechanism.As an extreme condition,high pressure is an important method to discover new materials and properties.The effect of pressure on the materials is mainly manifested by regulating the interaction within the material,and then changing the crystal structure or electronic structure of the materials.For example,phosphotene can transform from semiconductor to metallic phase under high pressure and occurs superconductivity at 5.5 GPa.Therefore,it is of great scientific significance to study the crystal structure and superconductivity of two-dimensional materials under high pressure.In this paper,two typical 2D materials tellurene and germanium sulfide（Ge S）are chosen to study the structure and properties of the 2D materials under high pressure.As an emerging member of 2D materials,tellurene has good stability and excellent photoelectric properties.Ge S is a typical layered compound semiconductor with a structure similar to black phosphorus.It has strong anisotropy in optical and electronic properties,and is found to be an ideal material for efficient solar cells and photodetectors.There are some controversies in the theoretical and experimental studies on the high-pressure structural phase transition of Ge S.The rule of phase transitions of tellurene and Ge S was obtained by Diamond anvil cell（DAC）and In situ high pressure powder X-ray diffraction（XRD）,and the relationship between the superconductivity of tellurene and pressure was determined experimentally.The results are as follows:1.The metallization of tellurene at pressure of about 1 GPa was found for the first time by electrical resistance measurements,and pressure-induced superconductivity was observed at pressure value of 1.2 GPa.T_cof tellurene reaches a maximum of 6.1 K at 34 GPa with the pressure increases.2.Tellurene undergoes three structural phase transitions when pressurized to46.1GPa from ambient pressure.The hexagonal phase tellurene transitions to monoclinic phase at 4.5 GPa,rhombohedral phase at 19.1 GPa,and cubic phase at30.9 GPa.3.Under non-hydrostatic pressure conditions,orthorhombic phase Pnma-Ge S is found to transition to monoclinic phase P2₁/m at 24.1 GPa and then to orthorhombic phase Cmcm at 33.1 GPa.Compared with previous research results,we find that the phase transition process of Ge S can be affected by hydrostatic pressure condition and different pressure media greatly.In this paper,we studied the effect of high pressure on superconductivity of 2D materials tellurene and the difference of properties between 2D material and bulk material under high pressure.The layered compound Ge S was chosen as a sample to study the structural changes of 2D materials under high pressure and the effect of hydrostatic pressure condition on the structural transitions of 2D materials.The results of this work provide a new direction for us to understand the structure of 2D materials and the relationship between superconductivity and high pressure.