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Quantum Phase Transitions in the Shastry-Sutherland Model for $\rm\bf SrCu_2 (BO_3)_2$

Akihisa Koga·Norio Kawakami
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Abstract

We investigate the quantum phase transitions in the frustrated antiferromagnetic Heisenberg model for $\rm SrCu_2(BO_3)_2$ by using the series expansion method. It is found that a novel spin-gap phase, which is adiabatically connected to the plaquette-singlet phase, exists between the dimer and the magnetically ordered phases known so far. When the ratio of the competing exchange couplings $α(=J'/J)$ is varied, this spin-gap phase exhibits the first- (second-) order quantum phase transition to the dimer (the magnetically ordered) phase at the critical point $α_{c1}=0.677(2)$ ($α_{c2}=0.86(1)$). Our results shed light on some controversial arguments about the nature of the quantum phase transitions in this model.

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Akihisa Koga, Norio Kawakami. 2000-03-28. Quantum Phase Transitions in the Shastry-Sutherland Model for $\rm\bf SrCu_2 (BO_3)_2$. https://doi.org/10.1103/physrevlett.84.4461

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