Theoretical Nanophysics

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Frustrated pyrochlores: from reentrance to magnetic monopoles

Ludovic Jaubert (Bordeaux)

03.12.2021 at 09:00 

What we colloquially know about frustration, is that it prevents
magnetic order. But the interesting part is not so much the absence of
something (here, of order), but rather what happens in its place. In
this talk we will see two different behaviours emerging from
frustration: reentrance and magnetic monopoles.

Reentrance is a recurring theme found in disparate physical systems,
from condensed matter to black holes. In this talk, we will explain the
microscopic mechanism behind reentrance in the frustrated pyrochlore
Er2Sn2O7 [1]. Taking advantage of the recent advance in the synthesis of
rare-earth stannate single crystal, and through detailed heat capacity
measurements, classical Monte Carlo simulations and classical linear
spin-wave expansions, we exhibit multiple instances of reentrance in
Er2Sn2O7, whose origins we argue are linked to soft-mode excitations and
zero-temperature phase transitions.

As for magnetic monopoles in spin ice [2], their signatures have been
indirect so far, leaving their direct observation an open challenge. One
such technique that could realize this direct observation is electron
holography. In this talk, we shall explore the possibility of imaging
monopoles via electron holography through experimental measurements of
spin ice analogs, and computational simulation of how monopoles would
appear in a pyrochlore spin ice thin film [3].

[1] D. R. Yahne et al, arXiv:2101.08361, to be published in PRL
[2] C. Castelnovo, et al. Nature 451, 42-45 (2008).
[3] A. Dhar, et al. in preparation



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