Speaker
Description
Magnetic order in gapped quantum antiferromagnets can be induced either by magnetic field or pressure. Such transitions are characterized by $z = 2$ or $z = 1$ dynamical critical exponents, determined by the quadratic or linear low-energy dispersion of their spin excitations, respectively. While the field-induced transitions (with the most common realization known as the Bose-Einstein magnon condensation) has been intensively studied, many details of the pressure-induced magnetic ordering has remained an open question. Employing high-pressure tunnel-diode-oscillator susceptibility, ultrasound, and high-field electron spin resonance spectroscopy measurements, we revealed pressure-induced magnetic ordering in the metal-organic material NiCl$_2\cdot 4$SC(NH$_2$)$_2$ (a.k.a. DTN), that we ascribe to the long-sought $z = 1$ criticality. This transition occurs at an easily accessible pressure of about $4.2$ kbar, allowing us to systematically study the low-temperature pressure-field phase diagram and establishing DTN as a perfect high-symmetry platform to investigate $z = 1$ quantum critical phenomena in solids.
Acknowledgements
The work was supported by the Deutsche Forschungsgemeinschaft as well as by HLD at HZDR, member of the European Magnetic Field Laboratory (EMFL).
References
[1] K. Yu. Povarov et al., “Pressure-tuned quantum criticality in the large-D antiferromagnet DTN,” Nature Communications, vol. 15, no. 1. Springer Science and Business Media LLC, Mar. 14, 2024. https://doi.org/10.1038/s41467-024-46527-x
