Dynamically induced magnetism in KTaO3

R. Matthias Geilhufe,Stefano Bonetti,Jian-Xin Zhu,Vladimir Juričić,Alexander V. Balatsky

doi:10.1103/physrevresearch.3.l022011

Abstract

Dynamical multiferroicity features entangled dynamic orders: fluctuating electric dipoles induce magnetization. Hence, the material with paraelectric fluctuations can develop magnetic signatures if dynamically driven. We identify the paraelectric KTaO3 (KTO) as a prime candidate for the observation of the dynamical multiferroicity. We show that when a KTO sample is exposed to a circularly polarized laser pulse, the dynamically induced ionic magnetic moments are of the order of 5% of the nuclear magneton per unit cell. We determine the phonon spectrum using ab initio methods, and we identify T1u as relevant phonon modes that couple to the external field and induce magnetic polarization. We also predict a corresponding electron effect for the dynamically induced magnetic moment, which is enhanced by several orders of magnitude due to the significant mass difference between electron and ionic nucleus.Received 12 March 2021Revised 9 April 2021Accepted 14 April 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.L022011Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLaser applicationsMagnetization dynamicsPhononsPhysical SystemsMultiferroicsParaelectricsPerovskitesPropertiesMagnetic momentPolarizationTechniquesDensity functional theoryTerahertz spectroscopyCondensed Matter, Materials & Applied Physics

Highlights

Dynamical multiferroicity [1], the phenomenon where fluctuating electrical dipoles induce magnetization, represents the dynamical counterpart of the Dzyaloshinskii-Moriya mechanism [2]
We show that when a KTO sample is exposed to a circularly polarized laser pulse, the dynamically induced ionic magnetic moments are of the order of 5% of the nuclear magneton per unit cell
From the perspective of the materials where dynamical multiferroicity can be realized, the prime candidate to search for the effect is SrTiO3 (STO), the paradigmatic quantum critical paraelectric where ferroelectricity is induced by displacive fluctuations

Summary

Introduction

Dynamical multiferroicity [1], the phenomenon where fluctuating electrical dipoles induce magnetization, represents the dynamical counterpart of the Dzyaloshinskii-Moriya mechanism [2]. Displacive paraelectrics (PE) exhibiting a ferroelectric (FE) phase transition [4,5,6,7,8,9,10,11] can display an elevated magnetic response induced by either quantum [12] or thermal fluctuations [13] close to the critical point. From the perspective of the materials where dynamical multiferroicity can be realized, the prime candidate to search for the effect is SrTiO3 (STO), the paradigmatic quantum critical paraelectric where ferroelectricity is induced by displacive fluctuations. Following the formalism of dynamical multiferroicity [1,12,13], we investigate the induction of magnetic moments by applying circularly polarized terahertz radiation resonant with the phonon frequency that yields fluctuating local electric dipoles, according to. As we show, using both single-mode approximation and the full dynamical matrix approach, when the system is subjected to a resonant circularly polarized laser pulse (Fig. 2), one

Published by the American Physical Society

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Findings

Conclusion and outlook