Magnons and continua in a magnetized and dimerized spin-12chain

Abstract

We examine the magnetic field dependent excitations of the dimerized spin-1/2 chain, copper nitrate, with antiferromagnetic intra-dimer exchange J1 = 0.44(1) meV and exchange alternation α = J2/J1 = 0.26(2). Magnetic excitations in three distinct regimes of magnetization are probed through inelastic neutron scattering at low temperatures. At low and high fields there are three and two long-lived magnon-like modes, respectively. The number of modes and the anti-phase relationship between the wave-vector dependent energy and intensity of magnon scattering reflect the distinct ground states: A singlet ground state at low fields µ0H < µ0Hc1 = 2.8 T and an Sz = 1/2 product state at high fields µ0H > µ0Hc2 = 4.2 T. In the intermediate field regime, a continuum of scattering forhω ≈ J1 is indicative of a strongly correlated gapless quantum state without coherent magnons.

Criticality-Enhanced Magnetocaloric Effect in Quantum Spin Chain Material Copper Nitrate

“…People have successfully discovered and synthesized plenty of spin materials which are very well described by the low-dimensional Heisenberg-type spin models. The long list includes, to name only a few, the diamond spin chain material azurite5, the kagome spin liquid herbertsmithite6, and Cu(NO 3 ) 2 ·2.5 H 2 O (copper nitrate hemipentahydrate, hereinafter referred to as “CN”) as an alternating Heisenberg antiferromagnetic chain (AHAFC)7891011121314151617181920212223242526272829.…”

“…It is one of the earliest inorganic spin chain material ever studied experimentally789101112131415161718192021222324252627282955, while continues intriguing people for its abundant physics including triplon wave excitation23 and precise Tomanaga-Lutting liquid behavior29. We notice that, despite many efforts, discrepancy in coupling constants still exists: the exact diagonalization (ED) fittings ( J  = 5.16 K, α  = 0.27) to thermodynamic quantities measurably deviates from those obtained from inelastic neutron scattering (INS) experiments ( J  = 5.14 K, α  = 0.227)26.…”

Tensor Network States and Effective Particles for Low-Dimensional Quantum Spin Systems

“…More specifically, non-trivial properties of the excitations can be probed with a high resolution in a lot of experiments, and an accurate understanding asks for a detailed account of the quasiparticles and their interactions. The most direct probe for low-energy spectra is inelastic neutron scattering, where multi-particle effects are becoming important [384,385]. The thermal broadening of one-particle signals can only be accounted for by many-particle processes [161].…”

Quasiparticle interactions in frustrated Heisenberg chains

“…In recent years, the interactions between these quasiparticles have come within the scope of experiments. Most importantly, the spectral functions as measured in inelastic neutron scattering (INS) experiments have important contributions from many-particle states [2][3][4][5] . Also, the thermal broadening of one-particle signals can only be accounted for by many-particle processes 6,7 .…”