Strongly Correlated Materials: Experiments and Computation
- Guy Cohen (Tel Aviv University, Israel)
- Alexander Shick (Institute of Physics ASCR, Czech Republic)
- Alexander Lichtenstein (University of Hamburg, Germany)
- Eitan Eidelstein (NRCN and Tel Aviv University, Israel)
Heavy fermion materials, transition metal oxides, and a variety of rare-earth compounds exhibit strong correlation: electrons in partially filled d and f shells of constituent atoms are delicately balanced between interaction-induced localization and kinetic delocalization , resulting in rich phase diagrams with remarkable and potentially useful switching properties . Most widespread computational approaches to materials, which are based on weak-correlation theories such as Density Functional Theory (DFT), Hartree-Fock and GW, fail to fully capture strong correlations.
The physics of strongly correlated electrons is of broad fundamental interest, with recent examples including the elusive theory of topological Kondo insulators [9, 28], the formation of multipolar orders in actinide oxides  and the controversial nature of high temperature superconductivity in plutonium-based materials [5, 10]. Some of the most societally pressing and yet long-standing issues involve the radioactive actinides [25, 20, 14], and better theoretical methods are critical to addressing nuclear waste remediation .
An emerging, cutting-edge generation of methods has begun addressing the challenge of performing realistic simulations of strongly correlated materials. Notable examples include the Dynamical Mean Field Theory (DMFT)  paired with continuous time quantum Monte Carlo (CT-QMC) , variational Monte Carlo [22, 21] and others . However, the problem remains extremely difficult, and attacking it requires a large-scale multidisciplinary effort. In this conference, we propose to bring together some major players working on various separate but synergistic sides of the problem, from both the theoretical and experimental perspectives.
From the theoretical perspective, significant progress towards a quantitative and general theory of d-electron and f-electron systems requires a combination of tools and approaches. Great strides have been made in DMFT [28, 14, 26, 13, 27]. However, advances towards a realistic description rely on a stronger connection to underlying weakly correlated theories [18, 19, 30]. They further rely on improved Monte Carlo methods able to address dynamical phase problems in the associated auxiliary problems [1, 4, 3, 7]. Promising new variational approaches should also be explored and hopefully integrated into the same toolset [2, 23], and all these ideas should be combined with modern methods for constructing coarse-grained models [15, 16]. Finally, close collaboration with experimentalists is paramount to focusing this effort.
We propose to bring together several prominent researchers in correlated electrons, f-electron materials, and the foundations and extensions of weakly correlated methods. All invitees develop unique and relevant computational or experimental methods. The emphasis is on members of several centers in the Czech Republic and Israel, between which we hope to form a long-term collaboration; however, a select group of leaders in the field from elsewhere will also attend.
The main emphasis is on theory and method development, and discussions are planned between experts from a diverse set of disciplines and scientific communities that have made relevant contributions to the field but would not normally meet each other. However, we also propose to put these theorists in close contact with experimentalists that have unique access to some of the most groundbreaking studies in Europe on strongly-correlated 5f systems, and provide tutorials on x-ray magnetic circular dichroism (XMCD), x-ray absorption near-edge structure (XANES), electron energy-loss spectroscopy (EELS), electron-probe microanalysis (EPMA), and transmission electron microscopy (TEM).
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