2014: Dr. Olga Volkova defended her Dr. Sci. thesis on «Quantum ground states in low-dimensional magnetics»

In November 2014, Dr. Olga Volkova (senior researcher, Chair of Physics of Low Temperatures and Superconductivity) defended her Dr. Sci. thesis on �Quantum ground states in low-dimensional magnetics�.

In this work the synthesis of new low–dimensional compounds was proposed and described for the first time. A new phenomenon of long range and short-range correlations formation was found in various low-dimensional magnets, specifically, in silicates, nitrates, phosphates and complex metal oxides. Unique experimental realizations of the theoretical models, i.e., “confederate flag” and �Shastry-Sutherland� were demonstrated.

Concentrated magnetic systems, which can not demonstrate long range order formation due to the crystal structure features can realize spin liquid state formation at low temperatures. These features are attributed either to low dimensionality of magnetic subsystem or to the frustration of magnetic exchange interactions. Despite three�dimensional cases two�dimensional magnets can order only at the absolute zero temperature, while one�dimensional systems remain disordered even at zero temperature. Spin liquid in low-dimensional magnets is strongly correlated state with properties similar to the superconducting condensate. Ground state of low�dimensional magnets can be separated by energy gap from the continuum of magnetic excitations, as it is realized in isolated S=1 chains. Isolated S=1/2 chain possesses gapless ground state. Energy gap in magnetic excitations spectrum of S=½ chain can be found due to the alternation of the magnetic exchange interactions. In the case of strong alternation the system is equal to the assembly of non�interacting dimmers.