Electronic Structure Of LSMO/LAO/STO Heterointerfaces

In the past decades,the interfaces between two insulating oxides LaAlO3(LAO)/SrTiO3(STO)have attracted broad attention due to the formation of a quasi-two-dimensional electron gas(q2DEG)at the interface.Despite extensive efforts in both theoretical and experimental aspects,the origin of quasi-two-dimensional electron gas at the LAO/STO interface is not yet completely understood.In this thesis,we have made a systematically study on the 4 Lai1-xSrxMnO3/3LaAlO3/4SrTiO3(4L1-xSxMO/3LAO/4STO)heterostructure for different Sr doping employing first principles calculations.The main results are:1)By comparing a few different doping ways,we found that,the electronic properties of 4LSMO/3LAO/4STO do not change significant.2)We have calculated the electronic properties of La1-xSrxMnO3/LaAlO3/SrTiO3 structure for the different amount of Sr doping.We found that,for 4LSMO/3LAO/4STO,a q2DEG appears at LAO/STO interfaces for x=0 or 1/3,while it disappears for x=2/3 or 1,which is in agreement with the experimental results.3)Doping has strong effects on the internal polarized electric field in LAO,and further induces the oxygen octahedrons distortion.For x<2/3,the charge transfer from t2g orbital of Mn to t2g orbital of Ti at interface,which release the internal electric field.In this case,the oxygen octahedrons distort slightly.For x?2/3,the charge transfer does not occur,the internal polarized electric field increase,which results in the larger oxygen octahedrons distortion.