Strongly correlated electrons in heterostructures:transport, magnetism, and superconductivity

8 December 2008 (Mon), 3:30 pm - 5:00 pm

4F seminar room, Collaborative Res. Bldg., Namiki site

Dr. Satoshi Okamoto

Materials Science and Technology Division, Oak Ridge National Lab., USA

Strongly correlated electrons in heterostructures:transport, magnetism, and superconductivity

Study of artificial heterostructures involving transition-metal oxides is one of the main topics of current materials science [1]. Among various oxides, of particular interest are correlated-electron systems which exhibit a variety of phenomena such as high-Tc superconductivity in cuprates. Correlated heterostructures are expected to become fundamental building blocks of future oxide electronics utilizing the novel properties of the oxides. Thus, understanding of the correlated electron behaviors at surfaces and interfaces is of crucial importance. In this talk, I will present the recent theoretical development in this field, including the following three topics.

1. Mott-insulator/metal interface [2,3]. It is shown that the spectral function in the interacting region is modified by the coupling with the metallic region, resulting in rather non-linear transport behavior.

2. Surface magnetic behavior of double-exchange ferromagnet for manganites [4]. The magnetic moment in abut-three-unit-cell-wide surface layers is found to decrease rapidly with increasing temperature. Possible improvement of the tunneling magnetoresistance effect is expected by supressing this behavior.

3. Superlattices of high-Tc cuprates [5]. We examine the possibility of enhanced superconductivity in heterostructures involving both the underdoped cuprates and overdoped cuprates by applying the cluster dynamical-mean-field methods.

Work in ORNL is supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy.

[1] For example, A. Ohtomo et al., Nature (London) 419, 378 (2002).

[2] S. Okamoto (unpublished).

[3] S. Okamoto, Phys. Rev. Lett. 101, 116807 (2008).

[4] S. Okamoto (unpublished).

[5] S. Okamoto and T. A. Maier, Phys. Rev. Lett. 101, 156401 (2008).

Dr. Masao Arai(新井正男)