The workshop is also supported by the Psi-k Network  and VASP .

 

Understanding the phenomenon of solid-state magnetism and devising its technological applications have been one of the main goals of condensed matter physics since its apparition [1]. In the second half of the twentieth century, the main focus of this field was in general on the first row of the transition metals (TM) and their compounds.  The elemental iron, cobalt and nickel - which are prototypical itinerant ferromagnetic metals – were intensively investigated. The magnetism of correlated insulators embodied by 3d TM oxides attracted no less attention; its principal mechanisms – double exchange and superexchange, Jahn-Teller interaction, orbital orders – were uncovered and their mutual interaction explored [2,3].

In the first two decades of the XXI century, research in solid-state magnetism is progressively shifting towards the exciting and much less understood domain of spin-orbit magnetism [4,5]. The materials hosting heavy d and f ions exhibit a multitude of unusual quantum states – multipolar orders, quantum spin and dimer-bond liquids, spin-orbit excitons, topological phases, fractional excitations – that defy the conventional paradigm of distinct spin and orbital degrees of freedom possessing different characteristic energy scales and symmetries.  The large spin-orbit interaction due to heavy nuclei of those ions couples the corresponding on-site moments leading to an emergence of spin-orbital-entangled ionic ground state. This spin-orbit entanglement is at the origin of phenomena cited above. Their rich physics arising due to intersite coupling between single-ion spin-orbit entangled states, their interaction with lattice degrees of freedom [5], applied field and external perturbations has stimulated vast research activity in this area as documented by several prominent review papers [6,7,8].

Progress in the field of spin-orbit magnetism is driven, first of all, by the ever increasing ability to synthesize high-purity materials, both in their bulk [9,10,11,12] and, more recently, in virtually perfect 2D form [13,14]. The organizers of this workshop have contributed to this emerging field by disclosing multipolar phases in correlated f electron systems [15,16,17] and 5d oxides [18,19], have developed advanced numerical techniques [20,21] and revealed the formation of spin-orbit symmetry-broken phases in 5d double perovskites [22,23].   Exotic quantum states in these materials emerge at rather low temperatures of several tens of Kelvins. Their detection and characterization represent a significant challenge to experiment. Conventional probes of the ordered magnetism, like the neutron diffraction, are often insensitive to high-rank multipolar moments that may have too small form-factors or generate no magnetic density at all. Hence, an array of alternative spectroscopic techniques like the resonant and non-resonant inelastic X-ray scattering, nuclear magnetic resonance, muon and Raman spectroscopies has been applied to resolve the nature of unconventional order parameters in spin-orbit materials [24,25,26].

Theory of spin-orbital magnetism has been developed along two virtually independent directions. The first route is based on semi-empirical tight-binding schemes of a target class of materials, from which one derives many-body effective Hamiltonians (MBEH) involving only the degrees of freedom that are relevant for low-energy (low-temperature) physics. Such Hamiltonians are subsequently solved by analytical or numerical many-body techniques. The emphasis is thus on the description of the low-energy many-body states and their responses. The second route employs ab initio density-functional theory (DFT) methods, fully taking into account the electronic structure of a given material. The low-energy physics emergent from the electronic structure is, in contrast, treated in a highly simplified way. Recently, an ab initio approach [26,27] merging DFT with dynamical mean-field theory (DMFT) [29,30] has been extensively applied to calculate electronic structure of spin-orbit materials [31], but due to high computational cost of treating low-temperature ordered phases its application to exotic orders in spin-orbit materials is still limited [32]. The focus of DFT(+DMFT) studies is thus usually on electronic high-energy properties and total energy of local-moment phases. Both the MBEH and DFT approaches have had some impressive successes [6,33,34] but the synergy between them remains underdeveloped [21].

Overall goal: It is the goal of this workshop to assemble both leading experts and younger researches on spin-orbit entangled magnetism from different domains – theoreticians of both DFT and MBEH leaning as well as experimentalists – to review the current progress in the field and, most importantly, to foster the mutual collaboration and synergy between theory and experiments to address and define actual challenges and future research directions. Focus session on: double perovskites, pyrochlores, Kitaev/honeycomb, candidate spin-liquid materials, multiferroics, 2D magnetism. 

 

Applications

There is no registration fee. Maximum number of participants: 60

There will be a poster session and a few contributed talks to which the participants are encouraged to contribute. Applications to participate can be made by sending an email to
magnetism2024@univie.ac.at
providing the following information:

First Name, Last Name:

Affiliation:

Career stage:

Motivation:

Topic of presentation:

Type of presentation (poster or contributed):

Registration deadline: April 15 2024

 

References

[1] Magnetism and Magnetic Materials, J. M. D. Coey, Cambridge University Press (2012).

[2] Simple Models of Magnetism, R. Skomski, Oxford University Press (2008).

[3] Transition Metal Compounds, D. I. Khomskii, Cambridge University Press (2014).

[4] P. Santini, S. Carretta, G. Amoretti, R. Caciuffo, N. Magnani, and G. H. Lander, Rev. Mod. Phys. 81, 807 (2009).

[5] Sergey V. Streltsov and Daniel I. Khomskii Phys. Rev. X 10, 031043

[6] G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009).

[7] W. Witczak-Krempa, G. Chen, Y. B. Kim, and L. Balents, Annu. Rev. Condens. Matter Phys. 5, 57 (2014).

[8] T. Takayama, J. Chaloupka, A. Smerald, G. Khaliullin, and H. Takagi, J. Phys. Soc. Jpn. 90, 062001 (2021).

[9] D. D. Maharaj, et al. Phys. Rev. Lett. 124, 087206 (2020).

[10] Liang Fu Phys. Rev. Lett. 115, 026401 (2015)

[11] G. Khaliullin, D. Churchill, P. P. Stavropoulos, and H.-Y. Kee, Phys. Rev. Research 3, 033163 (2021).

[12] A. Takahashi and H. Shiba, J. Phys. Soc. Jpn. 69, 3328 (2000).

[13] Huang, B. et al. Nature 546, 270–273 (2017).

[14] Soriano, D. et al. Nano Letters 20, 6225–6234 (2020).

[15] Leonid V. Pourovskii  and Sergii Khmelevskyi, PNAS 118 (14) e2025317118 (2021)

[16] L. V. Pourovskii, S Khmelevskyi, Phys. Rev. B 99 (9), 094439 (2019).

[17] SL Dudarev, P Liu, DA Andersson, CR Stanek, T Ozaki, C Franchini, Phys Rev. Materials 3 (8), 083802 (2019).

[18] Dario Fiore MOsca et al., Phys. Rev. B 103, 104401 (2021).

[19] L. V. Pourovskii, D. F. Mosca, and C. Franchini Phys. Rev. Lett. 127, 237201 (2021).

[20] L. V. Pourovskii, Phys. Rev. B 94, 115117 (2016).

[21] DF Mosca, LV Pourovskii, C Franchini Physical Review B 106 (3), 035127 (2022).

[22] L Lu, M Song, W Liu, AP Reyes, P Kuhns, HO Lee, IR Fisher, VF Mitrović

Nature comm. 8, 14407.

[23] VFM W. Liu, R. Cong, A. P. Reyes, I. R. Fisher Phys. Rev. B 97, 224103.

[24] P. Santini et al. Phys. Rev. Lett. 97, 207203 (2006).

[25] H.-H. Kung et al. Science 347, 1339 (2015).

[26] D. D. Maharaj et al. Phys. Rev. Lett. 124, 087206 (2020).

[27] V. I. Anisimov et al. Journal of Physics: Condensed Matter 9, 7359 (1997).

[28] A. I. Lichtenstein and M. I. Katsnelson, Phys. Rev. B 57, 6884 (1998).

[29] W. Metzner and D. Vollhardt, Phys. Rev. Lett., 62, 324 (1989).

[30] A. Georges and G. Kotliar, Phys. Rev. B, 45, 6479–6483 (1992).

[31] K. Haule and G. Kotliar, Nature Physics 5, 796 (2009).

[32] C Martins, M Aichhorn, and S Biermann, J. Phys.: Condens. Matter 29 263001 (2017).

[33] B. J. Kim et al. Phys. Rev. Lett.101, 076402 (2008).

[34] G. Chen, R. Pereira, and L. Balents, Phys. Rev. B 82, 174440 (2010).