大型放射光施設 SPring-8

Speaker: Dr. Adriana I. Figueroa

Language: English

Affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2)

Title: Insights into topological insulator thin films using x-ray absorption spectroscopy

Abstract:
Novel materials and developments for spintronic applications are among the most active and successful research topics in condensed matter physics. Topological insulators (TIs) [1] have been on the spotlight for such potential applications as they promise dissipationless carrier transport through their spin-momentum locked surface states. The main strategy for making practical use of TIs is believed to be by combination with magnetic materials, either by doping TIs with magnetic impurities [2] or at interfaces of thin film heterostructures [3]. In this talk, I will describe the properties of both magnetically doped TIs and magnetic heterostructures incorporating TI thin films grown by molecular beam epitaxy, as studied by x-ray absorption spectroscopy (XAS) in synchrotron radiation facilities (ALBA, ESRF and Diamond Light Source). XAS, extended x-ray absorption spectroscopy (EXAFS) and x-ray magnetic circular dichroism (XMCD) have provided us with unparalleled information about the electronic, local structure and magnetism of these novel materials [4]. Moreover, they have allowed us to investigate magnetic proximity effects [5, 6], as well as time- and layer-resolved magnetodynamics [7] of TI heterostructures by combination of XMCD with ferromagnetic resonance (FMR). Understanding and controlling such proximity effects are prerequisites for observation of exotic magneto-electric phenomena, such as the quantum anomalous Hall effect, as well as incorporation of TIs into future electronic and spintronic devices.

Keywords: topological insulator, thin films, molecular beam epitaxy, x-ray absorption spectroscopy, EXAFS, XMCD, magnetic proximity effects.

References
[1] M. Z. Hasan, C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010).
[2] Y. L. Chen et al., Science 329, 659 (2010).
[3] M. Li et al. Phys. Rev. Lett. 115, 087201 (2015); Z. Jiang, et al. Nano Lett. 15, 5835−5840 (2015); F. Katmis et al. Nature. 533, 513-518 (2016).
[4] A. I. Figueroa et al. Phys. Rev. B 90, 134402 (2014); A. I. Figueroa et al. J. Phys. Chem. C 119, 17344 (2015); S. E. Harrison et al. Appl. Phys. Lett. 107, 182406 (2015); S. E. Harrison et al. J. Phys.: Condens. Matter. 27, 245602 (2015); A. I. Figueroa et al. Sci. Rep. 6, 22935 (2016).
[5] A. A. Baker et al. Phys. Rev. B 92, 094420 (2015); A. I. Figueroa et al. J. Magn. Magn. Mater. 442, 93-99 (2017); L. B. Duffy et al. Phys. Rev. B 95, 224422 (2017).
[6] A. I. Figueroa et al. to be submitted (2019).
[7] A. A. Baker et al. Sci. Rep 5, 7907 (2015); A. I. Figueroa et al. J. Magn. Magn. Mater. 400, 178 (2016); A. A. Baker et al. J. Magn. Magn. Mater. 473, 470 (2019).

Website: https://icn2.cat/en/physics-and-engineering-of-nanodevices-group