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<span class="normaltextrun"><b><span style="font-size:26.0pt;font-family:"Times New Roman",serif;color:#006FC0">Physics & Astronomy Colloquium<o:p></o:p></span></b></span></p>
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<span class="normaltextrun"><i><span style="font-size:26.0pt;font-family:"Times New Roman",serif">Magnetooptical Infrared Spectroscopy of Magnetic Topological Materials</span></i></span><o:p></o:p></p>
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<span class="normaltextrun"><b><i><span style="font-size:28.0pt;font-family:"Times New Roman",serif">Dr. Badih A. Assaf</span></i></b></span><o:p></o:p></p>
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<span class="normaltextrun"><span style="font-size:26.0pt;font-family:"Times New Roman",serif">University of Notre Dame</span></span><span style="font-size:9.0pt;font-family:"Segoe UI",sans-serif"><o:p></o:p></span></p>
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<span class="normaltextrun"><b><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:black;background:white">Abstract:
</span></b></span><span class="normaltextrun"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:black;background:white">Magnetic topological materials have primarily been studied to realize the quantization of the Hall effect at zero magnetic
field which was discovered in 2013 [1]. The optical properties of these materials remain, however, nearly unharnessed. The gapless nature of topological states, combined with magnetic exchange opens interesting avenues for the development of polarization sensitive
sensing devices, at long wavelengths. In this context, my talk will discuss our recent magnetooptical infrared spectroscopy measurements on two types of topological insulators subjected to magnetism through the proximity effect and intrinsically. First, I
will discuss our observation of a strong infrared magnetic circular dichroism in the optical absorption of the intrinsic magnetic topological insulator MnBi2Te4 under applied magnetic field. The dichroism reaches 1.8% at 30T for a 40nm film, survives down
to 5T and likely originates from the splitting of the valence and conduction bands in the presence of a finite out-of-plane magnetization [2]. Second, I will present our scheme to artificially introduce magnetic exchange [3] into the high mobility topological
material Pb1-xSnxSe to realize a polarization sensitive response from surface states down to the far-infrared. The results that I will show motivate a deeper investigation of the infrared response of topological materials, which I argue can be relevant for
sensing devices.<o:p></o:p></span></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span class="normaltextrun"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:black;background:white">[1] Chang et al. Science 340 6129 (2013). [2] Bac et al. Npj Quantum Materials
7 46 (2022). [3] Wang et al. arxiv2207.07685<o:p></o:p></span></span></p>
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<span class="normaltextrun"><b><span style="font-size:18.0pt;font-family:"Times New Roman",serif;color:#2F5496">Thursday, October 20, 2022</span></b></span><span style="font-size:18.0pt;font-family:"Segoe UI",sans-serif;color:black"><o:p></o:p></span></p>
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<span class="normaltextrun"><b><span style="font-size:18.0pt;font-family:"Times New Roman",serif;color:#2F5496">3:40 PM in Winston Chung Hall (Room 138)</span></b></span><span style="font-size:18.0pt;font-family:"Segoe UI",sans-serif;color:black"><o:p></o:p></span></p>
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<span class="normaltextrun"><b><span style="font-size:18.0pt;font-family:"Times New Roman",serif;color:#2F5496">Coffee will be served at 3:10 PM in the Barkas Lounge (3049 Physics)</span></b></span><span style="font-size:18.0pt;font-family:"Segoe UI",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal">Heather McDermott<o:p></o:p></p>
<p class="MsoNormal">Travel & Events Coordinator<o:p></o:p></p>
<p class="MsoNormal">Physics & Astronomy Dept.<o:p></o:p></p>
<p class="MsoNormal">UC Riverside<o:p></o:p></p>
<p class="MsoNormal">3401 Watkins Dr.<o:p></o:p></p>
<p class="MsoNormal">Riverside, CA 92521<o:p></o:p></p>
<p class="MsoNormal">P: 951-827-5330<o:p></o:p></p>
<p class="MsoNormal"><span style="color:black">Available via Zoom Link: </span><span style="font-size:10.5pt;color:black;background:white"><a href="https://ucr.zoom.us/my/heathermcdermott">https://ucr.zoom.us/my/<span style="font-size:11.0pt">heathermcdermott</span></a></span><span style="color:black"><o:p></o:p></span></p>
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