Abstract
Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped quantum antiferromagnets can undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These transitions are characterized by z = 1 or z = 2 dynamical critical exponents, determined by the linear and quadratic low-energy dispersion of spin excitations, respectively. Employing high-frequency susceptibility and ultrasound techniques, we demonstrate that the tetragonal easy-plane quantum antiferromagnet NiCl2 ⋅ 4SC(NH2)2 (aka DTN) undergoes a spin-gap closure transition at about 4.2 kbar, resulting in a pressure-induced magnetic ordering. The studies are complemented by high-pressure-electron spin-resonance measurements confirming the proposed scenario. Powder neutron diffraction measurements revealed that no lattice distortion occurs at this pressure and the high spin symmetry is preserved, establishing DTN as a perfect platform to investigate z = 1 quantum critical phenomena. The experimental observations are supported by DMRG calculations, allowing us to quantitatively describe the pressure-driven evolution of critical fields and spin-Hamiltonian parameters in DTN.
| Original language | English |
|---|---|
| Article number | 2295 |
| Journal | Nature Communications |
| Volume | 15 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2024 |
Funding
We thank A. Mannig, J. Möller, and G. Perren for their involvement at the early stage of the ETH Zürich part of the project. This work was supported by the Deutsche Forschungsgemeinschaft through ZV 6/2-2, the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter - ct.qmat (EXC 2147, Project No. 390858490) and the SFB 1143 (Project No. 247310070), as well as by HLD at HZDR, member of the European Magnetic Field Laboratory (EMFL) [K.Yu.P., S.A.Zv., S.Zh., A.H., J.W.]. The neutron-diffraction experiments at HB2a used resources at the High Flux Isotope Reactor, a Department of Energy Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was partially supported by the Swiss National Science Foundation, Division II [A.Z.]. A portion of this work has been performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation Cooperative Agreement DMR-1644779 and the State of Florida [D.E.G.]. ESR experiments were performed at the High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University (proposal 19H0501 and 20H0501). Support of the ICC-IMR Visitor Program at Tohoku University is acknowledged [S.A.Zv.]. This work was partially supported by the Brazilian agencies CNPq (grant 304455-2021-0) and FAPESP (grant 2021-12470-8) [A.P.F.]. We also thank M. E. Zhitomirsky for fruitful discussions.