Report on
RIKEN–APW–APCTP Joint Workshop
“Recent trends in condensed matter physics”

Date: Jan.14–16, 2012
Place: Okochi Hall, RIKEN, Wako, Saitama, Japan

This workshop was held by the budget of

The Theory Forum, one of the activities in the program “Quantum Science of Strongly Correlated Systems” (Core Researcher: Prof. Yoshinori Tokura, University of Tokyo and RIKEN) in “World–Leading Innovative R&D on Science and Technology (FIRST Program)” funded for 4 years (2010–2014) by the Japan Society for the Promotion of Science.

and was regarded as one of the series of
Asian Pacific Workshop (Chairman: Prof. Fuchun Zhang, The University of Hong Kong),

External activity of Asian Pacific Center for Theoretical Physics.

Organizers are R. Arita, A. Furusaki, N. Kawakami, S. Maekawa, N. Nagaosa (Chair), and F. C. Zhang (alphabetical order). The scope of this workshop was to discuss the following themes in condensed matter physics. Topological aspects of condensed matter, Spintronics, Frustration and textures in spin systems, Strong correlation, and Superconductivity. The majority of the speakers are the theorists, and we also invite some distinguished experimentalists.

On the first day (Jan.14), there were 2 sessions. In the first session 1. “Strong correlation I”, several recent issues in theories of electron correlation have been discussed including the variational wavefunction, tensor product wavefunction, nonequilibrium properties, and holographic approach. In the second session 2. “Frustration and related phenomena”, both experimental studies (spin textures in helimagnets and their physical properties, spin liquid and non-Fermi liquids in frustrated lattice) and theoretical approaches (correlated topological insulators, realistic calculation of electron correlation and spin-orbit interaction) have been reported. In the poster session in the evening, 11 papers were presented and vivid discussion has been done.

On the next day (Jan.15), there were 3 sessions. In the first session 1. “Topological Phenomena”, various theoretical and experimental advances on topological insulators, and anomalous Hall effect have been reported. Transport experiment on Bi thin film, and STM studies of topological insulators were discussed as well as a theory of correlated topological insulator. Also a serious approach to the first-principles calculation of anomalous Hall effect was presented. In the afternoon session 2. “Spintronics”, the possible device application of domain wall systems manipulated by spin currents, an experimental study of transport in spin-orbit coupled system, and theories of spin motive force both in metals and insulators were reported. In Session 3. “Strong Correlation II”, experimental advances in iron based superconductors were discussed followed by three theory talks on correlated topological insulators, superfluid Fermi gas, and a variational wavefuction for t-J model.

On the last day, only one session “Superconductivity and related problems” has been held. Theoretical proposals to realize Majorana fermions, a theory of disorder effect on iron based superconductors, and a new fermionic approach to quantum spin chain systems were reported. Recent experimental studies on Sr2RuO4 have been also reported.

To summarize, even though the topics discussed were divergent, one can see some clear trends in current condensed matter theory. Especially, the interplay between the topological aspects of the electronic states and electron correlation is now an important issue, and its extension to superconductivity enriches the physics a lot. The development of first-principles band structure calculation begins to enable the predictions preceding the experimental studies. With the active participation of top researchers in this field, fruitful and stimulating discussion has been done during the workshop.
Jan. 17, 2012    Naoto Nagaosa