Effect Of Spin-Orbit Coupling On Electron Structure And Transport Properties Of Nano Materials With Inversion Asymmetry

Microelectronics has greatly promoted the development of the information industry.However,the uncontrollable factors of traditional microelectronic devices based on electronic charge properties are more obvious due to power consumption and quantum effects.Spintronic devices based on electron spin properties have emerged.The spin can be manipulated by an external magnetic field,but the introduction of the magnetic field limits the development of the device.The study of novel spintronics controlled by electric field provides the possibility to realize all-electric devices,and spin-orbitron is booming.The spin-orbit coupling effect in the low-symmetry system is obvious,which affects the electronic structure and magnetic properties of the material.In non-magnetic materials with low-symmetry,Rushba spin-orbit coupling can be used for spin-charge conversion,hence purely electrical spin injection and manipulation can be achieved without a magnetic field.In magnetic materials,spin-orbit coupling induce the Dzyaloshinskii-moriya interaction and chiral spin spiral,such as magnetic Skyrmions with topological protection.Both Rushba and chiral spin order have great application potential in the next generation of low-power information processing and storage applications.We use the first-principles calculation to study the electronic structure and transport properties of some low-dimensional systems with strong spin-orbit coupling and symmetry breaking,and have obtained some important research results.The main results of this paper are as follows:1.In the non-magnetic material Bi Sb,the symmetry breaking and the strong spin-orbit coupling form a huge Rashba effect,and the Rushba spin-orbit coupling plays an important role in carrier transport under external excitation such as electric field and heat.By combining density functional theory with Boltzmann transport theory,we study the effect of spine orbit coupling on thermoelectric properties of the two-dimensional Bi Sb monolayer.The results have shown that the Rashba spin-orbit coupling lead to a low-dimensional density of states and prolongs the relaxation time of carriers,thus significantly increasing the power factor.At room temperature,The Rashba spin splitting can improve the thermoelectric performance by 78%compared to the spin degeneracy system.The ZT value with Rashba spin-orbit coupling is 0.32.In addition,the maximum ZT value at 600 K is as high as 0.48.The high thermoelectric performance is also attributed to the low thermal conductivity because of the low group velocity of phonon and the intrinsic electric field.2.The collinear local magnetic moment appears in the pure platinum nano-junction,and has a large orbital magnetic moment.The introduction of oxygen atoms reduces the symmetry of the system.Dzyaloshinskii-moriya interaction induced by spin-orbit coupling competes with the isotropic magnetic exchange interaction,resulting in a chiral spin spiral.The magnitude and direction of magnetic moment in the Pt nanojunction change with the oxygen concentration.In addition,the results of magnetic transport indicate that the conductance is related to the magnetic state and the oxygen concentration.As the oxygen concentration increases,the magnetic resistance changes from a small negative value to a larger positive one.Thus oxygen concentration provides an effective means of regulating magnetic and magnetic transport.3.In the Janus magnetic transition metal chalcogenides VSSe and VSe Te,the symmetry of the system is broken,leading to the interaction of Dzyaloshinskii-Moriya interaction.By constructing a clockwise and counterclockwise helical magnetic sequence,the micromagnetic Dzyaloshinskii-Moriya interaction of VSe Te is calculated up to d=4.5m J/m~2,while VSSe is basically half of the former.Using the calculated magnetic parameters,the magnetic state of the Janus magnetic VSe Te was explored by micromagnetic simulation.The results show that the large in-plane magnetic anisotropy forms the Neel domain.In the smaller in-plane anisotropy,a specific magnetic field can induce stable Skyrmions.In the case of out-of-plane magnetic anisotropy,the Skyrmions can exist under zero magnetic field.Our research provides new ideas for finding new symmetry-deficient low-dimensional systems,and provides a theory for exploring the potential applications of Rashba and non-collinear magnetic sequence systems in thermoelectric and magnetic storage.