Bhattacharya A, May S J, te Velthuis S G E, Warusawithana M, Zhai X, Jiang Bin, Zuo J-M, Fitzsimmons M R, Bader S D, Eckstein J N
Materials Science Division and Argonne National Laboratory, Argonne, Illinois 60439, USA.
Phys Rev Lett. 2008 Jun 27;100(25):257203. doi: 10.1103/PhysRevLett.100.257203.
Superlattices of (LaMnO3){2n}/(SrMnO3){n} (1<or=n<or=5), composed of the gapped insulators LaMnO3 and SrMnO3, undergo a metal-insulator transition as a function of n, being metallic for n<or=2 and insulating for n>or=3. Measurements of transport, magnetization, and polarized neutron reflectivity reveal that the ferromagnetism is relatively uniform in the metallic state, and is strongly modulated in the insulating state, being high in LaMnO3 and suppressed in SrMnO3. The modulation is consistent with a Mott transition driven by the proximity between the (LaMnO3)/(SrMnO3) interfaces. The insulating state for n>or=3 obeys variable range hopping at low temperatures. We suggest that this is due to states at the Fermi level that emerge at the (LaMnO3)/(SrMnO3) interfaces and are localized by disorder.
由带隙绝缘体LaMnO₃和SrMnO₃组成的(LaMnO₃)₂ₙ/(SrMnO₃)ₙ（1≤n≤5）超晶格，会随着n的变化发生金属-绝缘体转变，n≤2时为金属态，n≥3时为绝缘态。输运、磁化和极化中子反射率测量结果表明，铁磁性在金属态相对均匀，而在绝缘态受到强烈调制，在LaMnO₃中较高，在SrMnO₃中受到抑制。这种调制与由(LaMnO₃)/(SrMnO₃)界面之间的接近程度驱动的莫特转变一致。n≥3时的绝缘态在低温下遵循变程跳跃。我们认为这是由于在(LaMnO₃)/(SrMnO₃)界面出现并因无序而局域化的费米能级态所致。
