위상양자물성 연구실에서 프랑스 파리대학의 Yann Gallais교수님을 초청하여 세미나를 개최합니다.

학과 구성원 여러분의 많은 참여를 부탁 드립니다.

○ Date/Time: July 25(Thur.) 4:30 pm

○ Place: Natural Science 1,  Room No. 31355
○ Speaker: Prof. Yann Gallais (MPQ, Université Paris Cité, Paris, France)
○ Title: Anisotropic strain control of Quantum Materials
○ Abstract: With their rich landscape of competing and intertwined electronic orders, quantum materials harbor a plethora of exotic electronic and magnetic phases. As such they offer a fertile platform to tune their properties via external parameters. An emerging tuning parameter to probe and control quantum materials is anisotropic strain. During the last decade, it has played a pivotal role to reveal spontaneous or incipient anisotropic electronic states, often dubbed nematicity. An applied anisotropic strain acts as a conjugate field of the nematic order in analogy to an applied magnetic field to a ferromagnet.
In the first part of my presentation I will discuss polarization-resolved Raman scattering measurements that aims at probing the evolution of nematic fluctuations under tunable strain in the normal and superconducting states of the paradigmatic iron-based superconductor Co-doped BaFe2As2. In the non-superconducting parent compound BaFe2As2 the strain-induced suppression of the nematic susceptibility follows the expected behavior of an Ising order parameter under a symmetry breaking field. For the superconducting compound, the suppression of the nematic susceptibility correlates with the decrease of the superconducting critical temperature Tc. The results indicate a significant contribution of nematic fluctuations to electron pairing and validate theoretical scenarios of enhanced Tc near a nematic quantum critical point [1,2].
Finally, at the end of my presentation, I will present very recent measurements on the tritelluride charge density wave (CDW) compound ErTe3. Here I will show that anisotropic strain can re-orient the direction of the CDW ordering vector. Furthermore our results reveal an initimate link between CDW order and a hitherto overlooked monoclinic lattice distortion.

[1] J. C. Philippe et al. Phys. Rev. Lett 129, 187002 (2022).
[2] J. C. Philippe et al. Phys. Rev. B 105, 024518 (2022).