Quantum Criticality and Spin Liquid Phase in the Shastry-Sutherland model

Abstract

Using the density-matrix renormalization group method for the ground state and excitations of the Shastry-Sutherland spin model, we demonstrate the existence of a narrow quantum spin liquid phase between the previously known plaquette-singlet and antiferromagnetic states. Our conclusions are based on finite-size scaling of excited level crossings and order parameters. Together with previous results on candidate models for deconfined quantum criticality and spin liquid phases, our results point to a unified quantum phase diagram where the deconfined quantum-critical point separates a line of first-order transitions and a gapless spin liquid phase. The frustrated Shastry-Sutherland model is close to the critical point but slightly inside the spin liquid phase, while previously studied unfrustrated models cross the first-order line. We also argue that recent heat capacity measurements in SrCu2(BO3)2 show evidence of the proposed spin liquid at pressures between 2.6 and 3 GPa.

Rise and fall of plaquette order in Shastry-Sutherland magnet revealed by pseudo-fermion functional renormalization group

“…It supports the existence of a spin liquid region between the plaquette and Neel phase proposed in Ref. [4]. Thus, the SS model is a strong candidate to host spin liquid, and SrCu 2 (BO 3 ) 2 offers exciting opportunity to realize and probe the elusive spin liquid phase.…”

“…As the Neel phase is approached, the broad maxima coalesce into a sharp peak at (π, π), after which η drops quickly. The peak location of degeneracy η at J 1 /J 2 = 0.82 serves as an accurate estimation for the transition from the spin liquid to the Neel phase, in excellent agreement with the phase boundary obtained from large scale DMRG [4].…”

“…A large body of theoretical works have established the existence of three phases, see e.g. [2] and [3,4] for a synopsis of earlier and recent results, respectively. The J 1 < J 2 /2 limit is exactly solvable and the ground state is a product state of diagonal dimers (spin singlets).…”

“…A recent density matrix renormalization group (DMRG) study [3] with cylinders of circumference up to ten sites yielded similar phase boundary J 1 /J 2 ∈ [0.675, 0.77] but a continuous pN transition with spin correlations supporting a deconfined quantum critical point. Another DMRG using cylinder circumference up to 14 sites concludes that a spin liquid phase exists in the window J 1 /J 2 ∈ [0.79, 0.82] be-tween the plaquette and the Neel phase [4]. A core difficulty in reaching a consensus is attributed to the near degeneracy of the competing orders in this region.…”

Quantum phases of ferromagnetically coupled dimers on Shastry-Sutherland lattice

“…The ground state of this system has Néel and dimer order for small and large J/J y limit respectively considering (J x = J y ). Corboz et al 43 predicted the existence of a plaquette phase between Néel and dimer region using the PEPS technique, whereas, very recently, Yang et al 44 predicted a spin liquid phase. While it's exact nature has been controversial, Ronquillo and Peterson 45 predicted the topological gs.…”