First Order Phase Transition in IrTe<sub>2</sub> Studied by Optical Second Harmonic Generation
ORAL
Abstract
Optical second harmonic generation (SHG) is a powerful and versatile technique used to study the electronic symmetry of surfaces and interfaces. Transition metal compounds, such as IrTe2, are ideal candidates for broken symmetry studies. X-ray diffraction measurements of IrTe2 reveal that when cooling below Tc,bulk ~ 280 K a first order structural bulk phase transition from 1x1x1 (at high temperatures) to 5x1x5 (at low temperatures) occurs. On the surface electron diffraction shows 1x1 to 5x1 phase change at Tc,surface ~ 270 K. To understand the nature of this transition, SHG coupled with azimuthal sample rotation is used to probe the phase change across Tc,surface. We observe the hysteresis loop of SHG intensity with a ΔT of ~ 3K, in agreement with the previous electron diffraction measurement. Four polarization combinations are utilized allowing sensitivity to both the in-plane (Te-Te bonds) and out-of-plane (Ir-Te bonds) surface responses. In addition, rotational anisotropy SHG measurements above and below Tc,surface yield distinct surface symmetry patterns. Comparing the results of SHG to bulk properties, key insight into the nature of the phase transition is obtained.
*Supported by U.S. NSF through grant No. DMR-1504226
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Presenters
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Joel Taylor
- Department of Physics and Astronomy, Louisiana State University