Abstract
Phase transitions of quantum dimer magnets can be explained in terms of Bose-Einstein condensation of magnons. Here we consider a natural extension of the dimer magnets to SU(4)-symmetric tetramer systems, which could be created with four nuclear-spin components (named “u,” “d,” “c,” and “s”) of 173Yb atoms in optical superlattices. We apply the cluster mean-field approximation to the SU(4) Heisenberg model on a tetramerized square lattice, and study the phase transition phenomena in the presence of the field that creates a population imbalance between the two components u,d and the other two c,s. When the population of the four components is balanced, the ground state is approximately given by the direct product of local SU(4)-singlet states. When the field is applied, the population ratio of the components u and d is increased and the system eventually reaches a “saturated” state, which is a SU(2) system with only u and d. We show that in the saturation process, the system exhibits two successive step-like transitions, in contrast to the standard dimer magnets with continuous transition process associated with Bose-Einstein condensation of magnons. The intermediate phase in between the two step-like transitions is a nontrivial solid phase with alternating arrangement of the SU(4)-singlet and four-site resonating-valence-bond states.
Highlights
Quantum dimer magnets, in which pairs of neighboring spins are strongly coupled as shown in Fig. 1(a), have been attracting attention as a prototypical example for studying exotic phases of matter characterized by quantum entanglement
Spin-dimer materials such as TlCuCl31,2 have a non-magnetic gapped ground state, which is approximately described by a direct product of spin-singlet states, due to the strong intradimer antiferromagnetic interactions
In this work, using the cluster mean-field approximation, we study the quantum phase transition phenomena from the SU(4)-singlet state under the field that creates a global population imbalance in the four flavors
Summary
In which pairs of neighboring spins are strongly coupled as shown in Fig. 1(a), have been attracting attention as a prototypical example for studying exotic phases of matter characterized by quantum entanglement. Spin-dimer materials such as TlCuCl31,2 have a non-magnetic gapped ground state, which is approximately described by a direct product of spin-singlet states, due to the strong intradimer antiferromagnetic interactions. Besides the conventional SU(2) systems, there has been success in realizing SU(N > 2) symmetric Mott insulators with alkaline-earth(-like) atoms such as 173Yb.8,9 Those atoms are closed-shell in the ground. In coldatom experiments, such a superlattice potential could be created by superimposing long-period and short-period optical lattices.. In this work, using the cluster mean-field approximation, we study the quantum phase transition phenomena from the SU(4)-singlet state under the field that creates a global population imbalance in the four flavors
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