Field-driven phase transitions in a quasi-two-dimensional quantum antiferromagnet

Abstract

We report magnetic susceptibility, specific heat, and neutron scattering measurements as a function of applied magnetic field and temperature to characterize the $S=1/2$ quasi-two-dimensional frustrated magnet piperazinium hexachlorodicuprate (PHCC). The experiments reveal four distinct phases. At low temperatures and fields the material forms a quantum paramagnet with a 1 meV singlet triplet gap and a magnon bandwidth of 1.7 meV. The singlet state involves multiple spin pairs some of which have negative ground state bond energies. Increasing the field at low temperatures induces three dimensional long range antiferromagnetic order at 7.5 Tesla through a continuous phase transition that can be described as magnon Bose-Einstein condensation. The phase transition to a fully polarized ferromagnetic state occurs at 37 Tesla. The ordered antiferromagnetic phase is surrounded by a renormalized classical regime. The crossover to this phase from the quantum paramagnet is marked by a distinct anomaly in the magnetic susceptibility which coincides with closure of the finite temperature singlet-triplet pseudo gap. The phase boundary between the quantum paramagnet and the Bose-Einstein condensate features a finite temperature minimum at $T=0.2$ K, which may be associated with coupling to nuclear spin or lattice degrees of freedom close to quantum criticality.

Submitted to New Journal of Physics

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Cited by in corpus (30)

• Bose-Einstein Condensation in Magnetic Insulators
• Quantum critical transport, duality, and M-theory
• Magnetic-Field Induced Bose-Einstein Condensation of Magnons and Critical Behavior in Interacting Spin Dimer System TlCuCl${}_3$
• Dirty-boson physics with magnetic insulators
• Magnetic field splitting of the spin-resonance in CeCoIn5
• Field-induced criticality in a gapped quantum magnet with bond disorder
• Singlet-triplet dispersion reveals additional frustration in the triangular dimer compound Ba${}_3$Mn${}_2$O${}_8$
• Dispersive magnetic excitations in the S=1 antiferromagnet Ba${}_3$Mn${}_2$O${}_8$
• Almost Perfect Frustration in the Dimer Magnet Ba${}_2$CoSi${}_2$O${}_6$Cl${}_2$
• Pressure-induced quantum critical and multicritical points in a frustrated spin liquid
• Crystals for neutron scattering studies of quantum magnetism
• Macroscopic properties of triplon Bose-Einstein condensates
• Excitations in a quantum spin liquid with random bonds
• High-field instability of field-induced triplon Bose-Einstein condensate
• Electron spin resonance study of anisotropic interactions in a two-dimensional spin gap magnet PHCC
• (CuCl)LaTa2O7 and quantum phase transition in the (CuX)LaM2O7 family (X = Cl, Br; M = Nb, Ta)
• On Josephson effects in insulating spin systems
• Field-concentration phase diagram of a quantum spin liquid with bond defects
• Magnetic field resonantly enhanced free spins in underdoped YBa${}_2$Cu${}_3$O${}_{6+x}$
• Dynamics of the two-dimensional S=1/2 dimer system (C5H6N2F)2CuCl4
• Magnons and continua in a magnetized and dimerized spin-1/2 chain
• Spin waves near the edge of halogen substitution induced magnetic order in Ni(Cl${}_{1-x}$Br${}_x$)${}_2$$\cdot$4SC(NH${}_2$)${}_2$
• Effect of disorder on a pressure-induced $z=1$ magnetic quantum phase transition
• Pressure-Induced Reentrant Oblique Antiferromagnetic Phase in Spin Dimer System TlCuCl_3
• Field induced non-BEC transitions in frustrated magnets
• Bose-Einstein Condensation of Magnons in NiCl2-4SC(NH2)2
• Formation of gapless triplets in the bond-doped spin-gap antiferromagnet (C${}_4$H${}_{12}$N${}_2$)(Cu${}_2$Cl${}_6$)
• Magnetic resonance of collective paramagnets with gapped excitations spectrum
• Formation of the S=1 paramagnetic centers in the bond-diluted spin-gap magnet
• One-dimensional physics of the frustrated quantum magnet PHCC