Quantum magnetism in spin, charge and orbital systems

2003.10.1-2003.10.4 at Paris

Sponsored by CNRS/DRI, CNRS/DRI, JSPS and French ambassy at Tokyo

Quantum magnetism is a frontier of magnetism. In the old view, magnetism is discussed with semi-classical concepts as ordered states, (sub)-lattice magnetization as the order parameter, spin-wave excitations. As it has been noticed since many years and by many authors, this modelization is insufficient to describe many experimental situations, specifically in low dimensional systems.

During the last fifteen years, a considerable amount of results both experimental and theoretical has been obtained for one-dimensional systems (1d). These remarkable progresses have been supported by major efforts in three directions:

From these coordinated efforts simple and beautiful pictures have emerged. Simplifying a bit, 1-d insulating quantum systems may: In two dimensions (2d), the variety of possible phases seems larger: On this way to a deeper understanding of what is going on in real materials, other issues appear as both timely and central: New experimental probe such as real space resolved spectroscopy (microscope, STM, micro-SQUID) and the probe for real time dynamics are necessary. Magnetic field is an important part of the studies; new quantum phases, tuning of quantum critical point and incommensurability control are very important. To answer these different questions, it is important to have good samples of old and new materials, and study their low energy excitations (far infra red and micro wave) as well as the high energy scale behaviors (X- rays, THz, high fields) and to encourage and initiate more and more collaborations between scientists creating the materials, experimentalists and theoreticians.

Collaborations have been made so far on non-linear excitations in the copper benzoates, Spin Peierls and Haldane compounds, magnetization plateaus, molecular magnetism, solid-state chemistry, NMR, neutron and ESR spectroscopy. We expect an extension of the collaborations in theory, NMR, ESR and neutrons, collaborations on new materials, and new techniques such as X-Ray (including high field experiments). We aim to tighten existing collaborations, try to launch an open and creative discussion on some of the challenging questions listed above, and initiate if possible new coordinated researches.