<div dir="ltr"><div dir="ltr"><div dir="ltr"><b><font color="#674ea7">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 </font></b><a href="https://utn.zoom.us/j/89038134365" target="_blank">https://utn.zoom.us/j/89038134365</a></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr"><div dir="ltr"><div dir="ltr" class="gmail_attr"><div dir="ltr"><div dir="ltr"><b><font color="#674ea7">Para acceder al espacio virtual, les pedimos que se identifiquen con su nombre a partir de 10:20hs.</font></b></div><div dir="ltr"><br></div><div dir="ltr"><b><font color="#674ea7"><br></font></b></div><div dir="ltr"><div dir="ltr" style="text-align:center"><b style="color:rgb(106,168,79)"><font size="4">Charla IFLYSIB VIRTUAL</font></b></div><div dir="ltr" style="text-align:center"><b style="color:rgb(106,168,79)"><font size="4">Viernes 23/09/2022, 10:30 hs. </font></b></div><div dir="ltr" style="text-align:center"><b style="color:rgb(106,168,79)"><font size="2">Link: </font></b><b><a href="https://utn.zoom.us/j/89038134365" target="_blank"><span>https://utn.zoom.us/j/89038134365</span></a></b></div><div dir="ltr" style="text-align:center"><br></div><div dir="ltr" style="text-align:center"><font size="2"><br></font></div></div></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr"><div dir="ltr"><div dir="ltr" class="gmail_attr"><div><span style="color:rgb(0,0,0)"><font size="2"><b><u>Título</u>:</b></font></span><span style="font-size:small;font-variant-numeric:normal;font-variant-east-asian:normal;font-family:calibri,sans-serif;color:rgb(17,85,204);font-weight:700;vertical-align:baseline;white-space:pre-wrap"><font size="2"> </font></span></div><div><b>Reentrance in frustrated systems</b></div><div><br></div><div dir="ltr" class="gmail_attr"><span style="color:rgb(0,0,0)"><u><font size="2"><b>Expositor</b></font></u><font size="2"><b>:</b>  <br></font></span></div><div dir="ltr" class="gmail_attr"><span style="color:rgb(0,0,0)"><font size="2"><b><strong class="gmail_sendername" dir="auto">Ludovic Jaubert </strong>- CNRS, Université de Bordeaux, LOMA, Talence, France</b></font></span><div><span style="color:rgb(0,0,0)"><b><span></span><u><br></u></b></span></div><div><span style="color:rgb(0,0,0)"><b><u></u></b></span></div><div><span style="color:rgb(0,0,0)"><b><u>Resumen</u>:</b></span><b><font size="2"><span style="font-family:calibri,sans-serif;color:rgb(17,85,204);font-variant-numeric:normal;font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap"><br></span></font></b></div><font color="#888888"><b></b></font><div><b>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.</b></div><div><b><br></b></div><div><b>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 <b><font size="2"><span style="font-weight:normal"><b><span id="gmail-MathJax-Element-1-Frame" class="gmail-mjx-chtml gmail-MathJax_CHTML" tabindex="0"><span id="gmail-MJXc-Node-1" class="gmail-mjx-math"><span id="gmail-MJXc-Node-2" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-3" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-4" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-5" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-6" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">Er</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-7" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-8" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-9" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-10" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-11" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">Sn</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-12" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-13" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-14" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-15" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-16" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">O</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-17" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-18" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.376em">7</span></span></span></span></span></span></span></span></span></b></span></font></b>. Monte Carlo simulations reproduce the multiple 
instances of reentrance measured experimentally via state-of-the-art 
heat capacity measurements of <font size="2"><span style="font-weight:normal"><b><span id="gmail-MathJax-Element-1-Frame" class="gmail-mjx-chtml gmail-MathJax_CHTML" tabindex="0"><span id="gmail-MJXc-Node-1" class="gmail-mjx-math"><span id="gmail-MJXc-Node-2" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-3" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-4" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-5" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-6" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">Er</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-7" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-8" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-9" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-10" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-11" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">Sn</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-12" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-13" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-14" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-15" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-16" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">O</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-17" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-18" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.376em">7</span></span></span></span></span></span></span></span></span></b></span></font>, 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.</b></div><div><br></div><div><u><b>Ref</b></u>: Yahne, Pereira, Jaubert, Sanjeewa, Powell, Kolis, Xu, Enjalran, Gingras & Ross,<font size="2"><span style="font-weight:normal"> <a href="https://doi.org/10.1103/PhysRevLett.127.277206">Understanding reentrance in frustrated magnets: The case of the <span id="gmail-MathJax-Element-1-Frame" class="gmail-mjx-chtml gmail-MathJax_CHTML" tabindex="0"><span id="gmail-MJXc-Node-1" class="gmail-mjx-math"><span id="gmail-MJXc-Node-2" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-3" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-4" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-5" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-6" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">Er</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-7" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-8" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-9" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-10" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-11" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">Sn</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-12" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-13" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.339em">2</span></span></span></span></span><span id="gmail-MJXc-Node-14" class="gmail-mjx-msub"><span class="gmail-mjx-base"><span id="gmail-MJXc-Node-15" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-16" class="gmail-mjx-mi"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.413em;padding-bottom:0.376em">O</span></span></span></span><span class="gmail-mjx-sub" style="vertical-align:-0.212em;padding-right:0.071em"><span id="gmail-MJXc-Node-17" class="gmail-mjx-mrow"><span id="gmail-MJXc-Node-18" class="gmail-mjx-mn"><span class="gmail-mjx-char gmail-MJXc-TeX-main-R" style="padding-top:0.376em;padding-bottom:0.376em">7</span></span></span></span></span></span></span></span></span> Pyrochlore</a>, </span></font>Phys. Rev. Lett. 127, 277206 (2021).<br></div></div></div></div></div></div></div></div></div></div></div><div><br></div><div><br></div><br>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><font size="4"><span style="font-family:arial"><b>Comisión ChIFLy</b></span></font></div><div><span style="font-family:arial;font-size:small">______________________________________________</span></div><span style="font-family:arial"><div style="font-size:small"><span style="font-family:arial;font-size:small"><br></span></div></span><span style="color:rgb(29,34,40);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif">Si no tenés interés en recibir los avisos de las chiflys, escribinos.</span><br></div></div></div></div></div></div></div></div></div>