Research

The group is mainly devoted to study of novel and advanced materials having appealing functionalities suitable for new electronic and spintronic devices.

We use mainly first-principles calculations based on density functional theory in order to simulate the structural, electronic and magnetic properties of materials. Moreover, we often use model Hamiltonian approaches as well as symmetry analysis to complement our ab-initio studies.

Our main results (in chronological order) have been:

• Discovery of new microscopic mechanisms of multiferroic and magnetic oxides (theme of ERC Starting Grant): first theoretical example of ferroelectricity induced by isotropic exchange (S. Picozzi et al, Phys. Rev. Lett. 99, 227201 (2017), and T. Aoyama, K. Yamauchi, A. Iyama, S. Picozzi, K. Shimizu & T. Kimura, Nat. Commun. 5, 4927 (2014)), ferroelectricity, induced by charge-ordering (M. Alexe, M. Ziese, D. Hesse, P. Esquinazi, K. Yamauchi, T. Fukushima, S. Picozzi, U Goesele, Adv. Mater. 21, 4452 (2009) or K. Yamauchi and S. Picozzi, Phys. Rev. Lett. 105, 107202 (2010) and by charge-spin ordering (see also S. Picozzi and C. Ederer, Topical Review on J. Phys.: Cond. Matt. 21, 303201 (2009))
• Design of ferroelectricity and multiferroicity in organic crystals: first example of a single component organic ferroelectric crystal, the croconic acid (see S. Horiuchi, Y. Tokunaga, G. Giovannetti, S. Picozzi, H. Itoh, R. Shimano, R. Kumai & Y.Tokura, Nature 463, 789 (2010) and Gianluca Giovannetti, Sanjeev Kumar, Alessandro Stroppa, Jeroen van den Brink, and Silvia Picozzi, Phys. Rev. Lett. 103, 266401 (2009)
• Design of ferroelectricity and multiferroicity in metal organic frameworks (MOF) (A. Stroppa, P. Barone, P. Jain, J.M. Perez-Mato, and S. Picozzi. Adv. Mater. 25, 2284 (2013) D. Di Sante, A. Stroppa, P. Jain, and S. Picozzi, Journal of the American Chemical Society, 135, 18126 (2013) , A. Stroppa, P. Jain, P.Barone , M. Marsman, J.M. Perez-Mato, A. Cheetham, H.W. Kroto and S. Picozzi, Angewandte Chemie- Intl Ed. Vol.: 50, 5847-5850 (2011) ). We also predicted controllable ferroelectricity and strong Rashba effects in a revolutionary MOF class, namely "solar" perovskites based on halides(A. Stroppa, D. Di Sante, P. Barone, M. Bokdam, G. Kresse, C. Franchini, M. Whangbo, S. Picozzi, Nat. Commun. 5, 5900 (2014)).
• Discovery by first principles of a new class of multifunctional materials, called "Ferroelectric Rashba semiconductors" (FERSC), represented by Gete (D. Di Sante, P. Barone, R. Bertacco, S. Picozzi, Adv. Mater. 25, 509 (2013) and subsequent experimental confirmation of our theoretical predictions, M. Liebmann et al, Adv. Mater. 28, 560 (2016)): FERSC not only have a gigantic spin-splitting Rashba, but they also show a full control over spin-texture by reversing the ferroelectric polarization. Since 2013, we have shown that many other materials are FERSC(Luiz Gustavo Davanse da Silveira, Paolo Barone, and Silvia Picozzi, Phys. Rev. B 93, 245159 (2016), Domenico Di Sante, Paolo Barone, Evgeny Plekhanov, Sergio Ciuchi, and Silvia Picozzi, Scientific Reports, 5:11285 (2015) and in some materials the Rashba effect coexists with spin-valley coupling (K. Yamauchi, P. Barone, T. Shishidou, T. Oguchi and S. Picozzi, Phys. Rev. Lett. 115, 037602 (2015))
• In the field of topological materials with strong spin-orbit interaction (i.e. Dirac, Weyl, Rashba, topological insulators), we predicted different alloys with Rashba, Dirac and Weyl (D. Di Sante, P. Barone, A. Stroppa, K. Garrity, D. Vanderbilt and S. Picozzi, Phys. Rev. Lett. 117, 076401 (2016) and A.Narayan, D. Di Sante, S. Picozzi, and S. Sanvito , Phys. Rev. Lett. 113, 256403 (2014)). We also successfully compared theoretical and experimental ARPES spectra with Weyl-materials, such as WTe2 (P. K. Das, D. Di Sante, I. Vobornik, J. Fujii, T. Okuda, E. Bruyer, A. Gyenis, B.E. Feldman, J. Tao, R. Ciancio, G. Rossi, M.N. Ali, S. Picozzi, A. Yadzani, G. Panaccione, and R.J. Cava, Nat. Commun. 7, 10847 (2016)) and in PbSnTe topological alloys with strong Rashba effects (V. V. Volobuev, P. S. Mandal, M. Galicka, O.Caha, J. Sánchez-Barriga, D. Di Sante, A. Varykhalov, A.Khiar, S. Picozzi, G. Bauer, P. Kacman, R. Buczko, O. Rader, and G. Springholz, Adv. Mater. 29, 1604185 (2017)).