Weak first-order quantum phase transition in the spin-tetrahedron system Cu(2)Te(2)O(5)Br(2) without lattice contributions
2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 13, 134403- p.Article in journal (Refereed) Published
Under pressure the spin tetrahedron system Cu(2)Te(2)O(5)Br(2) shows a softening of the collective magnetic mode whereas the energy of local spin-exchange processes increases. This apparent contradiction is due to the system's proximity to a quantum critical point induced by competing interactions that effectively decouple the tetrahedra. The high-pressure state is therefore nonmagnetic and dominated by valence bond excitations. Anomalies in the frequency and the intensity of magnetic Raman scattering are evidence for a weakly discontinuous evolution of the quantum critical state. In contrast, structural parameters as well as optical phonon modes evolve continuously with pressure without any sign for discontinuous criticality. No new low-energy excitations are observed. In contrast, the expected fingerprints of the spin-liquid phase are broadened due to Dzyaloshinskii-Moriya interactions.
Place, publisher, year, edition, pages
2011. Vol. 83, no 13, 134403- p.
IdentifiersURN: urn:nbn:se:su:diva-68834DOI: 10.1103/PhysRevB.83.134403ISI: 000289190100006OAI: oai:DiVA.org:su-68834DiVA: diva2:473753
authorCount :62012-01-072012-01-072012-01-07Bibliographically approved