Axion electrodynamics with magnetoelectric Chromia
ORAL
Abstract
Axion electrodynamics with magnetoelectric Chromia
Syed Q. A. Shah1, Ather Mahmood1, Allan. H. MacDonald2 and Christian Binek1
syedshah@huskers.unl.edu1, ather.mahmood@unl.edu1, macdpc@physics.utexas.edu2, cbinek@unl.edu1
1Department of Physics & Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588-0299, USA.
2Department of Physics, University of Texas at Austin, Austin, TX 78712
Abstract:
The magnetoelectric (ME) susceptibility, α , of ME materials such as Cr2O3 (Chromia) can be decomposed into a trace free tensor component and a pseudoscalar or axion piece component with isotropic ME response. Powder samples have been suggested as a pathway to fabricate isotropic ME materials which effectively only have a pseudoscalar ME response. However, activating a non-vanishing axion piece requires a ME field cooling protocol which tends to induce preferred axes. In our work we noticed shortcomings in the literature on ME powders where effects of the magnitude of the ME annealing field product on the ME response have been ignored. We investigate the evolution of ME susceptibility in powder chromia samples for various ME field cooling protocols. A strong dependence of the functional form of α vs. T of Chromia powders on the ME field cooling protocol is observed. It provides a pathway to realize the elusive isotropic ME response. In addition, we invest the macroscopic magnetic monopole response of an isotropic ME material when excited by the electric field of an electric point charge.
Syed Q. A. Shah1, Ather Mahmood1, Allan. H. MacDonald2 and Christian Binek1
syedshah@huskers.unl.edu1, ather.mahmood@unl.edu1, macdpc@physics.utexas.edu2, cbinek@unl.edu1
1Department of Physics & Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588-0299, USA.
2Department of Physics, University of Texas at Austin, Austin, TX 78712
Abstract:
The magnetoelectric (ME) susceptibility, α , of ME materials such as Cr2O3 (Chromia) can be decomposed into a trace free tensor component and a pseudoscalar or axion piece component with isotropic ME response. Powder samples have been suggested as a pathway to fabricate isotropic ME materials which effectively only have a pseudoscalar ME response. However, activating a non-vanishing axion piece requires a ME field cooling protocol which tends to induce preferred axes. In our work we noticed shortcomings in the literature on ME powders where effects of the magnitude of the ME annealing field product on the ME response have been ignored. We investigate the evolution of ME susceptibility in powder chromia samples for various ME field cooling protocols. A strong dependence of the functional form of α vs. T of Chromia powders on the ME field cooling protocol is observed. It provides a pathway to realize the elusive isotropic ME response. In addition, we invest the macroscopic magnetic monopole response of an isotropic ME material when excited by the electric field of an electric point charge.
*Financial support by Army Research Office through MURI W911NF-16-1-0472 and by the NSF/EPSCoR RII Track-1: Emergent Quantum Materials and Technologies, OIA-2044049 is acknowledged. The research was performed in part in the NNF: NNCI and the NCMN, supported by NSF under ECCS:2025208, and the NRI.
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Presenters
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Syed Qamar Abbas Shah
- University of Nebraska - Lincoln