[Todos] CHARLA IFLYSIB VIRTUAL - Viernes 23/09/2022 10:30 hs - Reentrance in frustrated systems

[Charlas IFLYSIB]

*Dada la situación actual en relación al COVID-19, el IFLySIB realiza sus
seminarios en formato virtual. Para ello, invitamos a la comunidad a
participar a través del link *https://utn.zoom.us/j/89038134365
*Para acceder al espacio virtual, les pedimos que se identifiquen con su
nombre a partir de 10:20hs.*


*Charla IFLYSIB VIRTUAL*
*Viernes 23/09/2022, 10:30 hs. *
*Link: **https://utn.zoom.us/j/89038134365
<https://utn.zoom.us/j/89038134365>*


*Título:*
*Reentrance in frustrated systems*

*Expositor**:*
*Ludovic Jaubert *- CNRS, Université de Bordeaux, LOMA, Talence, France

*Resumen:*
*Upon cooling, our intuition tells us that a system shall become more
ordered: for example from liquid to solid, or from paramagnetic to
ferromagnetic. However, exceptions exist, and a disordered phase sometimes
reappears at lower temperatures. This is the phenomenon of reentrance,
which is a recurring theme found in disparate physical systems, from
condensed matter to black holes. In addition to temperature, reentrance can
also take place upon variation of other external parameters; e.g. a system
might be paramagnetic at low and high fields, but magnetically ordered at
intermediate values.*

*In this seminar, we will present a historical and general introduction to
the phenomenon of reentrance, both in theory and experiments. In
particular, reentrance seems to be a common property of frustrated systems
in a magnetic field. However, a generic understanding of its underlying
mechanism is still lacking. Here, we will explain one of its microscopic
mechanism, taking the example of the antiferromagnetic pyrochlore Er2Sn2O7.
Monte Carlo simulations reproduce the multiple instances of reentrance
measured experimentally via state-of-the-art heat capacity measurements of
Er2Sn2O7, in three different field directions. Analysing these simulations
in light of classical linear spin-wave expansions, we will show that the
origin of this reentrance is linked to soft-mode excitations attached to
zero-temperature phase transitions, and discuss its consequence.*

*Ref*: Yahne, Pereira, Jaubert, Sanjeewa, Powell, Kolis, Xu, Enjalran,
Gingras & Ross, Understanding reentrance in frustrated magnets: The case of
the Er2Sn2O7 Pyrochlore <https://doi.org/10.1103/PhysRevLett.127.277206>, Phys.
Rev. Lett. 127, 277206 (2021).



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