Events

Department of Magnetic Reseach Seminar

Quantum Phenomena in Nature: superconductivity and novel magnetism in minerals

prof. dr Alexander N. Vasiliev

Low Temperature Physics and Superconductivity Department, Physics Faculty, M.V. Lomonosov Moscow State, Moscow, Russia

The amazing diversity of crystal structures and peculiar magnetic topologies found in minerals attracts increasing attention of condensed matter physicists interested in quantum cooperative phenomena at low temperatures.

Among recently discussed hot topics in this field are the pressure-induced superconductivity in calaverite AuTe₂ [1] and the formation of the gapped (gapless) quantum ground state in herbertsmithite ZnCu₃(OH)₆Cl₂ [2].

Various original results are presented on:

1. formation of the short-range order (valence bond crystal) in litidionate Na₂Cu₂Si₄O₁₁ [3]. The magnetism in litidionite is sensitive to the presence of water in the tunnel structure of this compound which enables unique opportunity to tune the spin gap in the series of compounds Na₂Cu₂Si₄O₁₁×xH₂O (0 ≤ x ≤ 2).
2. long-range magnetic order and magnetic phase diagrams in dugganite Pb₃TeCo₃V₂O₁₄ [4] and francisite Cu₃YSe₂O₈Cl [5]. The layered magnetic structures in these compounds are characterized by hierarchy of intraplane and interplane exchange interaction parameters which enables full investigation of their magnetic phase diagrams. Specific feature of Pb₃TeCo₃V₂O₁₄ is the two-step magnetic phase transition, while Cu₃YSe₂O₈Cl exhibits the metamagnetic behavior at low temperatures.

The trends in the studies of minerals and their synthetic analogues and plethora of exotic phenomena observed in this multitude of objects are briefly discussed with respect to correspondence of crystal structure, electronic and magnetic properties.

1. K. Kudo, H. Ishii, M. Takasuga, et al., J. Phys. Soc. Jpn. 82, 063704 (2013); S. Kitagawa, H. Kotegawa, H. Tou, et al., J. Phys. Soc. Jpn. 82, 113704 (2013).
2. A. Olariu, P. Mendels, F. Bert, et al., Phys. Rev. Lett.100, 087202(2008); D.V. Pilon, C.H. Lui, T.-H. Han, et al., Phys. Rev. Lett. 111, 127401 (2013).
3. A. Moreira dos Santos, …, O. Volkova and A.N.V, Phys. Rev. B 72, 092403 (2005).
4. M.M. Markina, …, S.V. Streltsov, and A.N.V, Phys. Rev. B 89, 104409 (2014).
5. K.V. Zakharov, …, O.S. Volkova, and A.N.V, Phys. Rev B (2014) – submitted.