Motivated by the exotic critical phenomena observed in the Shastry-Sutherland
material SrCu2​(BO3​)2​ \blue{[Jimenez {\it et al}, Nature {\bf 592}, 370
(2021); Cui {\it et al}, Science {\bf 380}, 1179 (2023)]}, we investigate the
ground state nature of the extended Shastry-Sutherland model (SSM) by the
state-of-the-art 2D tensor network method. Via large-scale simulations up to
20×20 sites, we identify a continuous phase transition between the
plaquette valence-bond solid (PVBS) phase and the antiferromagnetic (AFM) phase
accompanied by an emergent O(4) symmetry, which strongly suggests a deconfined
quantum critical point (DQCP). Furthermore, we map out the phase diagram of the
extended SSM and observe the same type of DQCP phenomena with emergent O(4)
symmetry and similar critical exponents along the whole critical line. Our
results indicate a compelling scenario for understanding the origin of the
proximate DQCP observed in recent experiments.Comment: 5+6 pages; 4+5 figures; 3 table