Field-induced bound-state condensation and spin-nematic phase in SrCu${}_2$(BO${}_3$)${}_2$ revealed by neutron scattering up to 25.9 T

Abstract

Bose-Einstein condensation (BEC) underpins exotic forms of order ranging from superconductivity to superfluid 4 He. In quantum magnetic materials, ordered phases induced by an applied magnetic field can be described as the BEC of magnon excitations. With sufficiently strong magnetic frustration, exemplified by the system SrCu${}_2$(BO${}_3$)${}_2$ , no clear magnon BEC is observed and the complex spectrum of multi-magnon bound states may allow a different type of condensation, but the high fields required to probe this physics have remained a barrier to detailed investigation. Here we exploit the first purpose-built high-field neutron scattering facility to measure the spin excitations of SrCu${}_2$(BO${}_3$)${}_2$ up to 25.9 T and use cylinder matrix-product-states (MPS) calculations to reproduce the experimental spectra with high accuracy. Multiple unconventional features point to a condensation of $S=2$ bound states into a spin-nematic phase, including the gradients of the one-magnon branches, the presence of many novel composite two- and three-triplon excitations and the persistence of a one-magnon spin gap. This gap reflects a direct analogy with superconductivity, suggesting that the spin-nematic phase in SrCu${}_2$(BO${}_3$)${}_2$ is best understood as a condensate of bosonic Cooper pairs. Our results underline the wealth of unconventional states yet to be found in frustrated quantum magnetic materials under extreme conditions.

References in corpus (12)

• The density-matrix renormalization group in the age of matrix product states
• Bose-Einstein Condensation in Magnetic Insulators
• A quantum magnetic analogue to the critical point of water
• Incomplete devil's staircase in the magnetization curve of SrCu2(BO3)2
• Phase diagram of the Shastry-Sutherland Compound SrCu2(BO3)2 under extreme combined conditions of field and pressure
• Multiple Magnon Modes and Consequences for the Bose-Einstein Condensed Phase in BaCuSi2O6
• Uniform and staggered magnetizations induced by Dzyaloshinskii-Moriya interactions in isolated and coupled spin 1/2 dimers in a magnetic field
• Unveiling new quantum phases in the Shastry-Sutherland compound SrCu2(BO3)2up to the saturation magnetic field
• Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu${}_2$(BO${}_3$)${}_2$
• Thermally populated versus field-induced triplon bound states in the Shastry-Sutherland lattice SrCu${}_2$(BO${}_3$)${}_2$
• Magnetic field induced bound states in spin-$\frac{1}{2}$ ladders
• Investigating field-induced magnetic order in Han Purple by neutron scattering up to 25.9 T

Cited by in corpus (9)

• Emergent criticality in fully frustrated quantum magnets
• Possible Observation of Quadrupole Waves in Spin Nematics
• Frustration and chirality in three-dimensional trillium lattices: Insights and Perspectives
• Triplons, triplon pairs and dynamical symmetries in laser-driven Shastry-Sutherland magnets
• Anomalous thermal broadening in the Shastry-Sutherland model and SrCu${}_2($BO${}_3{)}_2$
• Dynamics of quantum spin-nematics: Comparisons with canted antiferromagnets
• Bullet pressure-cell design for neutron scattering experiments with horizontal magnetic fields and dilution temperatures
• Possible Bose-Einstein condensation of magnons in a S = 5/2 honeycomb lattice
• Coupled dimerized alternating-bond quantum spin chains in the distorted honeycomb-lattice magnet Cu${}_5$SbO${}_6$