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TT: Fachverband Tiefe Temperaturen

TT 50: Correlated Electrons: Frustrated Magnets - Low-Dimensional Systems

TT 50.3: Vortrag

Mittwoch, 22. März 2017, 15:30–15:45, HSZ 304

Ground-state phase diagram of the J₁−J₁′−J₂ chain — •Cliò Efthimia Agrapidis^{1, 2}, Stefan-Ludwig Drechsler¹, Jeroen van den Brink^{1, 2}, and Satoshi Nishimoto^{1, 2} — ¹Institute for Theoretical Solid State Physics, IFW Dresden, 01069 Dresden, Germany — ²Department of Physics, Technical University, Dresden, 01069 Dresden, Germany

Quasi one-dimensional (1D) frustrated systems, despite their simple structure, are at the center of attention as a playground for novel ground states that can emerge from frustration and strong quantum fluctuations due to low dimensionality. Motivated by the extensive interest in this field and by recent experimental results, we study the one-dimensional Heisenberg model with dimerized nearest-neighbor ferromagnetic (J₁, J₁^′<0) and next-nearest-neighbor antiferromagnetic (J₂>0) couplings using the spin-wave theory and the density-matrix renormalization group technique. Based on the numerical calculations of total spin, spin gap, equal-time spin-spin correlation functions, and Tomonaga-Luttinger spin exponent, we present the ground-state phase diagram in the space of frustration ratio (α=J₂/|J₁|) and dimerization degree (β=J₁^′/J₁). We find a first-order transition between fully-polarized FM and incommensurate singlet state at α_c=(β/2)/(1+β) and we suggest the existence of a crossover between an AKLT-type valence bond solid state and a frustration-induced dimerized state in the gapped phase. In the absence of dimerization (β=1), the spin gap opens at 1/4<α 1.52. Relevance to the quasi-one-dimensional frustrated compounds LiCuSbO₄ and Rb₂Cu₂Mo₃O₁₂ is also discussed.