The role of the interfaces in heterostructures of complex oxides

Understanding the new states at the interfaces and the resulting whole behavior of the heterostructures and multilayers is a hot topic at the forefront of the fundamental research, as demonstrated by the huge number of theoretical and experimental studies published in the topmost level scientific journals. In this context, strongly electron correlated oxides are attracting an increasing attention because of their possible practical applications in the emerging field of oxide electronics [1]. With the recent advances in thin-film fabrication, controlled growth of unit-cell layers of complex oxides opened new perspectives in the study of interface effects. In fact, a wealth of microscopic phenomena may be at the work at the interface between the constituent oxides and can result in a number of novel functional properties [2]. In this seminar, I will present two particular examples of unexpected electronic and magnetic interfacial phenomena in multilayers based on complex oxides: ferromagnetism, at the interface of two antiferromagnetic insulating constituent materials [3] and superconductivity, at the interface of two insulating oxides [4]. To disentangle the role of each constituent block and disclose the mechanism giving rise to the interfacial properties, elemental sensitive spectroscopic techniques can be extremely useful. In particular, I will describe the results obtained with two state-of-art synchrotron radiation techniques, namely polarization dependent soft x-ray absorption spectroscopy and bulk sensitive hard x-ray photoelectron spectroscopy.

[1] A.P. Ramirez, Science 315, 1377 (2007); E. Dagotto, Science 318, 1076 (2007).

[2] P. Zubko et al. Annu. mso-ansi-language:EN-US">Rev. Condens. Matter. Phys. 2, 141 (2011); H. Y. Hwang et al. Nature Materials 11, 103 (2012)

[3] C. Adamo et al. Appl. mso-ansi-language:EN-US">Phys. Lett. 92, 112508 (2008); A. Bhattacharya et al. Phys. Rev. Lett. 100, 257203 (2008)

[4] EN-US;mso-fareast-language:IT">G.Balestrino et al. Phys. Rev.B 58, R8925 (1998); A. Gozar et al., Nature 455, 782-785 (2008); C. Aruta et al., Phys. mso-bidi-font-style:italic">Rev. B 78, 205120 (2008)

[5] C.Aruta et al. mso-ansi-language:EN-US">Phys. Rev. B 80, R140405 (2009)

[6] D. Di Castro et al. cond-mat arXiv:1107.2239