Universität zu Köln

Grams, Christoph P., Valldor, Martin, Garst, Markus ORCID: 0000-0001-5390-3316 and Hemberger, Joachim (2014). Critical speeding-up in the magnetoelectric response of spin-ice near its monopole liquid-gas transition. Nat. Commun., 5. LONDON: NATURE PUBLISHING GROUP. ISSN 2041-1723

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Abstract

Competing interactions in the so-called spin-ice compounds stabilize a frustrated ground state with finite zero-point entropy and, interestingly, emergent magnetic monopole excitations. The properties of these monopoles are at the focus of recent research with particular emphasis on their quantum dynamics. It is predicted that each monopole also possesses an electric dipole moment, which allows to investigate their dynamics via the dielectric function epsilon(v). Here we report on broadband spectroscopic measurements of epsilon(v) in Dy2Ti2O7 down to temperatures of 200 mK with a specific focus on the critical end point present for a magnetic field along the crystallographic [111] direction. Clear critical signatures are revealed in the dielectric response when, similarly as in the liquid-gas transition, the density of monopoles changes in a critical manner. The dielectric relaxation time tau exhibits a critical speeding-up with a significant enhancement of 1/tau as the temperature is lowered towards the critical temperature. Besides demonstrating the magnetoelectric character of the emergent monopole excitations, our results corroborate the unique critical dynamics near the monopole condensation transition.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Grams, Christoph P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Valldor, Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED Garst, Markus UNSPECIFIED orcid.org/0000-0001-5390-3316 UNSPECIFIED Hemberger, Joachim UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-429737
DOI:	10.1038/ncomms5853
Journal or Publication Title:	Nat. Commun.
Volume:	5
Date:	2014
Publisher:	NATURE PUBLISHING GROUP
Place of Publication:	LONDON
ISSN:	2041-1723
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MAGNETIC MONOPOLES Multiple languages Multidisciplinary Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/42973