Artificial Charge-Modulation in Atomic-Scale Perovskite Titanate Superlattices

  • Grazul J.
  • Hwang H.
  • Muller D.
  • Ohtomo A.

The nature and length scales of charge screening in complex oxides is fundamental to a wide range of systems, spanning ceramic varistors, oxide tunnel junctions, and charge-ordering in mixed valence compounds. There are wide variations in the degree of charge disproportionation, length scale, and orientation in these latter configurations, but little is known about their microscopic electronic structure, a matter of intense theoretical scrutiny. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi 3+ O3 embedded in SrTi 4+ O3. Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity arising from superlattices of two constituent insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five Ti 3+ layers is required for the center titanium site to recover bulk-like electronic properties. This represents a new framework within which the short-length-scale electronic response can be probed and incorporated in thin film oxide heterostructures.

View Original Article

Recent Publications

January 01, 2018

Fair Dynamic Spectrum Management for QRD-Based Precoding with User Encoding Ordering in Downstream Transmission

In next generation DSL networks such as, employing discrete multi-tone transmission in high frequencies up to 212 MHz, the crosstalk among lines reaches very high levels. To precompensate the crosstalk in downstream transmission, QRD-based precoding has been proposed as a near-optimal dynamic spectrum management (DSM) technique. However, the performance ...

January 01, 2018

Practical Mitigation of Passive Intermodulation in Microstrip Circuits

This paper presents new experimental evidence and a novel practical approach for mitigation of passive intermodulation (PIM) in microstrip circuits fabricated on commercial printed circuit board laminates. The mechanisms of distributed PIM in microstrip circuits are reviewed and a phenomenology of PIM generation due to locally enhanced electromagnetic fields at ...

January 01, 2018

Efficient Cooperative HARQ for Multi-Source Multi-Relay Wireless Networks

In this paper, we compare the performance of three different cooperative Hybrid Automatic Repeat reQuest (HARQ) protocols for slow-fading half-duplex orthogonal multiple access multiple relay channel. Channel State Information (CSI) is available at the receiving side of each link only. Time Division Multiplexing is assumed, where each orthogonal transmission occurs ...