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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif"">The CME Seminar this week is presented by Adrian Gozar from Brookhaven National Laboratory on Thursday, October 4<sup>th</sup> at 11:30am in the Smith Seminar room.</span>
<br>
<br>
<span style="font-size:12.0pt;font-family:"Georgia","serif"">TITLE: <b>“Gapped sliding phononic modes in the incommensurate structure of the ladder-chain system Sr<sub>14</sub>Cu<sub>24</sub>O<sub>41</sub>”<o:p></o:p></b></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif"">ABSTRACT: I will discuss low energy Raman and infrared (IR) excitations in Sr<sub>14</sub>Cu<sub>24</sub>O<sub>41</sub>. Two modes are observed in the 1-2 meV range starting
from room temperature: one Raman and one IR active. A new IR excitation around 1 meV develops below the charge-ordering temperature T<sub>C</sub> ~ 150 K. We associate these modes with the gapped sliding motions of the charged CuO<sub>2</sub> chain and Sr<sub>2</sub>Cu<sub>2</sub>O<sub>3</sub>
ladder layers. This approach is able to quantitatively explain the range and relative energies of these resonances which are sensitive probes of the charge and spin ordering in the '14-24-41' systems.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif"">In the second part of the talk I will present my current research interests which are related to optical spectroscopy at the nano-scale. I will discuss what motivated us to develop
a variable-temperature scanning near-field spectroscopy system, what we did so far and where we want to go in the future.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif"">Thank you,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Georgia","serif"">Trisch<o:p></o:p></span></p>
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