Continuous and Discontinuous Quantum Phase Transitions in a Model Two-Dimensional Magnet

Abstract

The Shastry-Sutherland model, which consists of a set of spin 1/2 dimers on a 2-dimensional square lattice, is simple and soluble, but captures a central theme of condensed matter physics by sitting precariously on the quantum edge between isolated, gapped excitations and collective, ordered ground states. We compress the model Shastry-Sutherland material, SrCu2(BO3)2, in a diamond anvil cell at cryogenic temperatures to continuously tune the coupling energies and induce changes in state. High-resolution x-ray measurements exploit what emerges as a remarkably strong spin-lattice coupling to both monitor the magnetic behavior and the absence or presence of structural discontinuities. In the low-pressure spin-singlet regime, the onset of magnetism results in an expansion of the lattice with decreasing temperature, which permits a determination of the pressure dependent energy gap and the almost isotropic spin-lattice coupling energies. The singlet-triplet gap energy is suppressed continuously with increasing pressure, vanishing completely by 2 GPa. This continuous quantum phase transition is followed by a structural distortion at higher pressure.

16 pages, 4 figures. Accepted for publication in PNAS

References in corpus (4)

• Quantum spin liquid states in the two dimensional kagome antiferromagnets, ZnxCu4-x(OD)6Cl2
• A Novel Ordered Phase in SrCu2(BO3)2 under High Pressure
• In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu(2-x)Mgx(BO3)2
• Impurity-induced singlet breaking in SrCu2(BO3)2

Cited by in corpus (17)

• Observation of a 4-spin Plaquette Singlet State in the Shastry-Sutherland compound SrCu2(BO3)2
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• Phase diagram of the Shastry-Sutherland Compound SrCu2(BO3)2 under extreme combined conditions of field and pressure
• Direct Observation of the Quantum Phase Transition of SrCu${}_2$(BO${}_3$)${}_2$ by High-Pressure and Terahertz Electron Spin Resonance
• Sign-switching of dimer correlations in SrCu${}_2$(BO${}_3$)${}_2$ under hydrostatic pressure
• Emergent O(4) symmetry at the phase transition from plaquette-singlet to antiferromagnetic order in quasi-two-dimensional quantum magnets
• SrCu${}_2$(BO${}_3$)${}_2$ under pressure: a first-principle study
• Revealing three-dimensional quantum criticality by Sr-substitution in Han Purple
• Topographic control of order in quasi-2D granular phase transitions
• Frequency Extension to THz Range in High Pressure ESR System and Its Application to Shastry-Sutherland Model Compound SrCu${}_2$(BO${}_3$)${}_2$
• Fluctuation-induced ferrimagnetism in sublattice-imbalanced antiferromagnets with application to SrCu${}_2$(BO${}_3$)${}_2$ under pressure
• Signatures of the finite-temperature mirror symmetry breaking in the $S$=1/2 Shastry-Sutherland model
• Tensor network study of the Shastry-Sutherland model with weak interlayer coupling
• Triplons, triplon pairs and dynamical symmetries in laser-driven Shastry-Sutherland magnets
• Criticality and magnetic phases of Ising Shastry-Sutherland candidate holmium tetraboride
• Anomalous thermal broadening in the Shastry-Sutherland model and SrCu${}_2($BO${}_3{)}_2$
• Spiral Phase and Phase Diagram of the $S$=1/2 XXZ Model on the Shastry-Sutherland Lattice