Quantum Critical Dynamics in Magnetoelectric Multiferroics

磁电多铁性材料中的量子临界动力学

• 批准号: 233992164
• 负责人: Professor Dr. Joachim Hemberger
• 金额: --
• 依托单位: Institut für Experimentalphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233992164?language=en
• 关键词: Quantum; Critical; Dynamics; Magnetoelectric; Multiferroics

In this project we will examine the magneto-electric properties of transition-metal oxides by means of broadband dielectric spectroscopy. The efforts shall focus on the dynamics in the vicinity of critical end-points which at low temperatures are determined by quantum fluctuations. In the respected class of materials complex magnetic order is coupled to the onset of electric polarization or at least polarizability. Thus the external magnetic field can be utilized as control parameter for the ground state while the coupled magnetoelectric excitations can be examined via electric-field spectroscopy. For this purpose during the last years an experimental setup was developed to perform measurements of the complex permittivity in the frequency range from 1 mHz to 10 GHz, in external magnetic fields up to 15 T, and for temperatures down to 25 mK.The exceptional experimental sensitivity of this setup allows for the investigation of dynamical processes in the regarded temperature and energy range (1 GHz ~ 50 mK ~ 4 Micro-eV) which is not reachable by other methods, especially considering the width of the possible frequency range. The material basis which is to be studied reaches from the multiferroic quantum-spin chain LiCuVO4 or the ferromagnetic and magnetoelectric system Cu2OSeO3 to the spin-ice Dy2Ti2O7 for which a coupling of the magnetic monopole excitations to electric dipole moments was postulated. The particular combination of experimental methodology and material class can open unrivaled prospects for the understanding of the so far only sparely examined dynamical aspects in the vicinity of quantum phase transitions.

在这个项目中，我们将通过宽带介电光谱来研究过渡金属氧化物的磁电性质。重点研究低温下由量子涨落决定的临界端点附近的动力学。在受尊重的材料类别中，复杂的磁性顺序与电极化或至少极化率的开始相耦合。这样就可以利用外加磁场作为基态的控制参数，同时可以利用电场谱分析来检测耦合的磁电激励。为此，在过去几年中，开发了一种实验装置，用于测量频率范围为1 mHz至10 GHz，外部磁场高达15 T，温度低至25 mK的复介电常数。该装置的特殊实验灵敏度允许在所考虑的温度和能量范围（1 GHz ~ 50 mK ~ 4 Micro-eV）内进行动力学过程的研究，这是其他方法无法达到的。特别是考虑到可能的频率范围的宽度。要研究的物质基础从多铁量子自旋链LiCuVO4或铁磁磁电体系Cu2OSeO3到自旋冰Dy2Ti2O7，其中磁单极激发与电偶极矩的耦合是假设的。实验方法和材料类别的特殊结合可以为理解迄今为止仅很少研究的量子相变附近的动力学方面开辟无与伦比的前景。

项目成果

Interplay between antiferrodistortive, ferroelectric, and superconducting instabilities in Sr1-x Ca-x TiO3-delta

Sr1-x Ca-x TiO3-delta 中反铁畸变、铁电和超导不稳定性之间的相互作用

• DOI: 10.1103/physrevb.91.045108
• 发表时间: 2015
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: B. S. de Lima;M. S. da Luz;F. S. Oliveira;L. M. S. Alves;C. A. M. dos Santos;F. Jomard;Y. Sidis;P. Bourges;S. Harms;C. P. Grams;J. Hemberger;X. Lin;B. Fauqué;K. Behnia
• 通讯作者: K. Behnia

Critical slowing down near the multiferroic phase transition in MnWO4.

• DOI: 10.1103/physrevlett.114.037204
• 发表时间: 2014-08
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: D. Niermann;C. Grams;P. Becker;L. Bohatý;H. Schenck;J. Hemberger