Quantum Magnets: Frustration and Topology in Experiment and Theory

PhD Symposium of the Division of Magnetism and the Young DPG

March 21st, 2017, Dresden

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The Symposium

Every year at the DPG spring meeting a group of PhD students has the chance to organize a symposium on a topic they are interested in. In this framework a group of five PhD students from the Technical University Braunschweig will organize a Symposium on frustrated quantum magnets at the next DPG spring meeting in 2017 in Dresden.

Quantum magnetism is a very active area of condensed matter physics. In the last decades, this fascinating field has highly profited from the fruitful interplay of experiment and theory. It is a genuinely interdisciplinary area of research, linking across many different subfield boundaries, ranging from condensed matter and statistical physics, via ultra cold atomic gases, spin- and heat caloritronics, classical and quantum information theory, to questions in material design and device technology.
Frustrated quantum magnets can be realized in spin systems in which localized magnetic moments interact through competing exchange interactions that cannot be simultaneously satisfied. Such spin systems may be frustrated due to a multitude of reasons, e. g., quantum chemistry can lead to competing exchange paths or lattice geometry can induce frustration. Furthermore, spin-orbit interactions may lead to pseudo-spins with frustrating compass interactions and higher-order exchange can generate frustration through ring exchange. On the classical level frustration gives rise to a large degeneracy of the system’s ground state. Frustration occurs due to geometrical reasons or higher order exchange processes. On the quantum level this might lead to the emergence of unconventional solid and liquid phases with exotic excitations. In this context, the possibility of spin liquids is quite interesting from a theoretical as well as from an experimental point of view. While in early days spin liquids have merely been considered to be magnets which lack any type of long range order down to T=0, it has only been realized very recently that such liquids are a novel form of correlated matter which shows topological order and intimately linked to that, fractionalized excitations. In theory, the formation of such matter defies a description in terms of standard Ginzburg-Landau theory and it seems fair to say, that its physics is far from being understood. In experiment, first potentially promising candidates may have been synthesized, such as e. g. triangular magnets in organics, quantum spin ice on pyrochlores, and Kitaev model variants in iridates. Yet, the search for definite materials is still ongoing.
All in all, the study of frustrated quantum magnets reveals new physics and generates contributions to the development of novel materials. The investigation of quantum magnets is however a challenging problem. On the theoretical side numerous sophisticated methods have been developed and applied to gain insight into the properties of spin models, e. g. emergent gauge, and topological field theories, DMRG methods, tensor networks, variational Monte-Carlo and others. On the experimental side extensive material design has to be combined with a multitude of state-of-art probes, like nuclear magnetic resonance (NMR) and muon spin resonance (mu-SR), RIXS, INS, Raman, electron and tunneling spectroscopies as well as transport, high magnetic field, and thermodynamic measurements in order to identify potentially interesting compounds.

 

Invited Speakers

For the PhD symposium 2017, the following  invited speakers are already confirmed :

 

Schedule

This symposium is divided into three sessions. The first session is chosen to give an overview about frustrated quantum magnets and topological matter. Therefore, world's leading experts are invited to give two tutorials on theory as well as on experimental aspects. The second session focuses on the theoretical research of quantum magnets with two invited talks and one contributed talk. After the lunch break the session continues with two focused research talks with a representative selection of recent experimental highlights and another selected contributed talk.

The symposium will take place on 21st March 2017 from 9:30 (room HSZ 04).

9:30 - 09:45     Welcome and Introduction
Tutorial Session
09:45 - 10:30 M. Vojta Frustrated Quantum Magnets: Theory
10:30 - 11:15 B. Gaulin Ground State Selection in Quantum Pyrochlore Magnets
11:15 - 11:30 Coffee break                         
Theory Session
11:30 - 12:00 N. Perkins Effects of anisotropic exchange in strong spin-orbit coupled magnets
12:00 - 12:30 S. Rachel Numerical Approaches to Quantum Magnets
12:30 - 12:45 J. Stolpp Thermal and spin transport properties of frustrated spin-1/2 chains in high magnetic fields
12:45 - 13:45 Lunch break                         
Experimental Session         
13:45 - 14:15 P. Mendels Nuclear Probes on Frustrated Magnets
14:15 - 14:45 V. Zapf Complex spin structures and multifunctional magnetism

14:45 - 15:00

U. Tutsch Dimensional reduction due to geometric frustration - a case study

 

PhD symposium: Contributed talks and posters

The final program of the spring meeting has been released and can be found here.

We are very pleased about the large number of contributions for talks and posters. However, due to this large number, the talks will take place on Wednesday, 22nd of March, from 15:00 to 17:30 in room HSZ 403 (details can be found here). Moreover the contributed posters will be presented in a joined session on Friday, 24th of March, from 9:30 (details can be found here).

Organization committee

Please feel free to contact us via e-mail .

If you interested in our research, visit the institute's homepage of condensed matter physics or theoretical physics .

 

Organization team
(from left to right: Boris Celan, Leonie Heinze, Niklas Casper, Jonas Richter, Benjamin Köhler)

See also

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