Font Size: a A A

Manipulation Of Geometric Phase By Electric Fields

Posted on:2019-01-07Degree:MasterType:Thesis
Country:ChinaCandidate:C LiFull Text:PDF
GTID:2310330569989677Subject:Theoretical Physics
Abstract/Summary:PDF Full Text Request
The concept of geometric phase has penetrated into most fields of physics since the Berry phase has been proposed.Over the past three decades,people gradually realize that the geometric phase of the electronic wave-function can produce a profound effect on the properties of materials,especially on the transportation.On the other hand,the geometric phase also affects many physical phenomena such as spin polarization,orbital magnetism,various quantum/abnormal/spin Hall effects and quantum charge pumping and so on.For example,the charge will acquire a space-dependent phase when it moves in circle within an external magnetic field,which is normally called AharonovBohm effect and has been experimentally verified on the last century.While the Aharonov-Casher effect,is dual to the Aharonov-Bohm effect,originates from the coupling between spin and orbital momentum of particles.That means that the neutral particle could also produce an Aharonov-Casher phase and it is popularly investigated by recent experiments.Due to the fact that AC effect involves spin degrees of freedom,the investigation about AC phase help us to overcome the non-local problems in manipulating the electrons by magnetic field,meanwhile,it also provides a new methods to control spins and design new spin-devices.In this work,we aimed to find a proficient way to control spins by investigating the influences of geometric phase on magnetic systems and spin transportation.As we all know,the most researches about geometric phases demand that the systems evolved adiabatically with time and the calculations of nonadiabatic phase are too complex to solve.Besides,in the study of the effect of geometric phase on the properties of electron transport,most people believe that the electron spins precess around a fixed axis in mesoscopic systems.However,we used algebraic dynamics theories to easily calculate the geometric phase under arbitrary conditions,and proposed spin instantaneous precession,which means that spins precess around a various axis.We studied the spin transport in the one-dimensional AC ring model and proposed an effective method to control spins by electric fields.The results show that due to the presence of the geometric phase,the spin will instantaneously precess during electron transportation,which plays an important role on interference of electrons,which results in the spin polarization and spin flips when it through the AC ring.By numerical calculations,we found that the perpendicular electric field can efficiently induce a spin current and spin flips.At the same time,we applied the geometric phase to the magnetic system,considering the self-generated polarization generated by the non-collinear spin structures,and study the modulation effect of the AC phase on the spin structure,which shows that the geometric phase induced by the spin texture will affect back to magnetic orders in magnetic lattices.
Keywords/Search Tags:Berry Phase, Aharonov-Casher Effect, Non-collinear Spin, Spontaneous Polarization, Incommensurate Order, Spin Transportation, Algebra Dynamic Theory
PDF Full Text Request
Related items