Professor Adrian Feiguin, Department of Physics, Northeastern University Boston, MA, 02115, USA
Magnetism is intrinsically a quantum phenomenon dictated by the collective behavior of individual atomic moments. This “quantumness” is enhanced for half-integer spins S = 1/2 and could give rise to exotic quantum phases of matter without a classical analog. Quantum magnets present an exciting playground to realize Bose-Einstein condensation and 'quantum crystals'', for instance. I will report on the magnetic phase diagram of two interesting examples: the dimerized quantum magnet SrCu2(BO3)2, and the free radical magnet NIT-2Py. In both cases we conduct large-scale numerical simulations using the Density Matrix Renormalization Group method (DMRG) to shed light on the nature and structure of the different magnetic phases. The first example (SrCu2(BO3)2) can be described as a realization of the paradigmatic Shastry-Sutherland model, and we find the emergence of fractionally filled bosonic crystals in mesoscopic patterns, specified by a sequence of magnetization plateaus.
In the second case, first principles calculations show that NIT-2Py can be described as a quasi-two-dimensional arrangement of tetramers. Their spatial arrangement and the structure of the interactions yield a rich phase diagram with the presence of a half-magnetization plateau, and two unusual Bose-Einstein condensates where only half of the spins contribute to the superfluid density.
Site web du groupe du Pr Feiguin
Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et le Département de génie physique de Polytechnique Montréal.
