Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An excellent example of a controlled QPT is the field-induced ordering of a gapped quantum magnet. Although numerous "quasi-one-dimensional"coupled spin-chain and -ladder materials are known whose ordering transition is three-dimensional (3D), quasi-two-dimensional (2D) systems are special for multiple reasons. Motivated by the ancient pigment Han purple (BaCuSi2O6), a quasi-2D material displaying anomalous critical properties, we present a complete analysis of Ba0.9Sr0.1CuSi2O6. We measure the zero-field magnetic excitations by neutron spectroscopy and deduce the spin Hamiltonian. We probe the field-induced transition by combining magnetization, specific-heat, torque, and magnetocalorimetric measurements with nuclear magnetic resonance studies near the QPT. With a Bayesian statistical analysis and large-scale Quantum Monte Carlo simulations, we demonstrate unambiguously that observable 3D quantum critical scaling is restored by the structural simplification arising from light Sr substitution in Han purple.

Revealing three-dimensional quantum criticality by Sr substitution in Han purple

Mira A.;
2021-01-01

Abstract

Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An excellent example of a controlled QPT is the field-induced ordering of a gapped quantum magnet. Although numerous "quasi-one-dimensional"coupled spin-chain and -ladder materials are known whose ordering transition is three-dimensional (3D), quasi-two-dimensional (2D) systems are special for multiple reasons. Motivated by the ancient pigment Han purple (BaCuSi2O6), a quasi-2D material displaying anomalous critical properties, we present a complete analysis of Ba0.9Sr0.1CuSi2O6. We measure the zero-field magnetic excitations by neutron spectroscopy and deduce the spin Hamiltonian. We probe the field-induced transition by combining magnetization, specific-heat, torque, and magnetocalorimetric measurements with nuclear magnetic resonance studies near the QPT. With a Bayesian statistical analysis and large-scale Quantum Monte Carlo simulations, we demonstrate unambiguously that observable 3D quantum critical scaling is restored by the structural simplification arising from light Sr substitution in Han purple.
2021
Allenspach, S.; Puphal, P.; Link, J.; Heinmaa, I.; Pomjakushina, E.; Krellner, C.; Lass, J.; Tucker, G. S.; Niedermayer, C.; Imajo, S.; Kohama, Y.; Kindo, K.; Kramer, S.; Horvatic, M.; Jaime, M.; Madsen, A.; Mira, A.; Laflorencie, N.; Mila, F.; Normand, B.; Ruegg, C.; Stern, R.; Weickert, F.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/2124122
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