Abstract
The Shastry-Sutherland lattice, one of the simplest systems with geometrical frustration, which has an exact eigenstate by putting singlets on diagonal bonds, can be realized in a group of layered compounds and raises both theoretical and experimental interest. Most of the previous studies on the Shastry-Sutherland lattice are focusing on the Heisenberg model. Here we opt for the Hubbard model to calculate phase diagrams over a wide range of interaction parameters, and show the competing effects of interaction, frustration and temperature. At low temperature, frustration is shown to favor a paramagnetic metallic ground state, while interaction drives the system to an antiferromagnetic insulator phase. Between these two phases, there are an antiferromagnetic metal phase and a paramagnetic insulator phase (which should consist of a small plaquette phase and a dimer phase) resulting from the competition of the frustration and the interaction. Our results may shed light on more exhaustive studies about quantum phase transitions in geometrically frustrated systems.
Highlights
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Our study based on Hubbard model can provide phase diagrams that include a wider range of interaction parameters
As mentioned in the introduction part, most of the theoretical and numerical studies of Shastry-Sutherland lattice are focusing on localized spins based on the Heisenberg model, whose ground state phase diagram has two limiting behavior depending on the dimensionless parameter J/J9, where J is the exchange coupling constant along the nearest neighbour bonds and J9 the one along the additional diagonal bonds
Summary
The Shastry-Sutherland lattice is one of geometrically frustrated systems, and has been actively studied due to the magnetization plateaus in the presence of a magnetic field[8,9,10,11,12,13,14] and its observation[15,16,17,18,19,20] It was first proposed by Shastry and Sutherland[21] as a theoretical toy model with the Heisenberg Hamiltonian where there are exchange interactions on the nearest bond as well as the diagonal bonds (see in Fig. 1 (b)). Our study based on Hubbard model can provide phase diagrams that include a wider range of interaction parameters To understand this strongly correlated many-body system with geometrical frustration, we apply the cellular dynamical mean field theory (CDMFT) combined with the continuous time quantum Monte Carlo method (CTQMC).
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