Speaker
Prof.
Carlo Maria Canali
(Linnaeus University)
Description
Molecular quantum spintronics is an emerging field in condensed matter physics and nanoscience that combines concepts of spintronics and molecular electronics.
The present talk deals with theoretical investigations of molecular quantum spintronics with magnetic molecules, based on density functional theory (DFT). These molecules consist of a core of a few transition-metal (TM) atoms carrying a spin, connected and exchanged-coupled through bridging oxo-ligands. The core is surrounded by organic ligands which stabilize the structure and protect the magnetic properties of the molecule. Chemical synthesis allows a powerful and flexible control of the physical properties of the molecule by altering the individual TM and ligand atoms. In our study we are interested in two different classes of magnetic molecules. The first class comprises single-molecule magnets (SMMs), of which Mn12 acetate is the most famous representative. These are molecules that possess a high ground-state spin (S ~ 10) and a large magnetic anisotropy barrier, so that at low enough temperatures (T ~ 50 K) they behave like tiny nanomagnets, and possibly can store information in a spin electronic device. The second class consists of spin-frustrated molecules. One example is the triangular Cu3 complex. The lack of inversion symmetry permits an external electric field to couple efficiently the two lowest states of the molecule having opposite spin chirality [Loss2008, Islam2010]. Molecules displaying efficient spin-electric couplings are in high demand for quantum computation since they can be used to encode and manipulate spin qbits electrically. In the last few years we have carried out extensive theoretical work on both types of molecules, based on spin DFT calculations. In this talk we will review some of the challenges in developing a satisfactory first-principles description of these molecules based on DFT. The issues investigated include: i. the feasible handling of spin-orbit interactions to evaluate properties such as the magnetic anisotropy energy, relevant for SMMs such as Mn12 [Michalak2010, Nossa2013]; ii. the need of employing multi-determinant many-body wave functions to describe frustrated ground states in antiferromagnetic triangular molecules [Islam2010, Nossa 2012, 2013, Islam2017]; iii. the limitations that DFT must face in describing molecules functionalized onto solid surfaces or wired to the metal electrodes of a molecular junction device [Nossa 2013, Pertsova2015].
References
[Islam2010] Md F. Islam, J.F. Nossa, C.M. Canali and M.R. Pederson, Phys. Rev. B 82, 155446 (2010).
[Islam2010] Md F. Islam, J.F. Nossa, M.R. Pederson and C.M. Canali, preprint 2017.
[Loss2008] M. Trift, F. Troiani, D. Stepanenko and D. Loss, Phys. Rev. Lett 101, 217201 (2008).
[Michalak2010] L. Michalak, C.M. Canali, et al., Phys. Rev. Lett. 104, 017202 (2010).
[Nossa2012] J.F. Nossa, Md F. Islam, C.M. Canali and M.R. Pederson, Phys. Rev. B 85 85427 (2012).
[Nossa2013] J.F. Nossa, Md F. Islam, C.M. Canali and M.R. Pederson, Phys. Rev. B 88, 224423 (2013).
[Pertsova2015] A. Pertsova, C.M. Canali, M.R. Pederson, I. Rungger and S. Sanvito, Molecular and Optical Physics, 64, 29 (2015).
Primary author
Prof.
Carlo Maria Canali
(Linnaeus University)
