CMSA Strongly Correlated Quantum Materials and High-Temperature Superconductors Series: Signatures of anomalous symmetry breaking in the cuprates

CMSA EVENTS

Speaker:

David Hsieh - Caltech

The temperature versus doping phase diagram of the cuprate high-T_c superconductors features an enigmatic pseudogap region whose microscopic origin remains a subject of intensive study. Experimentally resolving its symmetry properties is imperative for narrowing down the list of possible explanations. In this talk I will give an overview of how optical second harmonic generation (SHG) can be used as a sensitive probe of symmetry breaking, and recap the ways it has been used to solve outstanding problems in condensed matter physics. I will then describe how we have been applying SHG polarimetry and spectroscopy to interrogate the cuprate pseudogap. In particular, I will discuss our data on YBa₂Cu₃O_y [1], which show an order parameter-like increase in SHG intensity below the pseudogap temperature T* across a broad range of doping levels. I will then focus on our more recent results on a model parent cuprate Sr₂CuO₂Cl₂ [2], where evidence of anomalous broken symmetries surprisingly also exists. Possible connections between these observations will be speculated upon.

[1] L. Zhao, C. A. Belvin, R. Liang, D. A. Bonn, W. N. Hardy, N. P. Armitage and D. Hsieh, “A global inversion-symmetry-broken phase inside the pseudogap region of YBa₂Cu₃O_y,” Nature Phys. 13, 250 (2017).

[2] A. de la Torre, K. L. Seyler, L. Zhao, S. Di Matteo, M. S. Scheurer, Y. Li, B. Yu, M. Greven, S. Sachdev, M. R. Norman and D. Hsieh. “Anomalous mirror symmetry breaking in a model insulating cuprate Sr₂CuO₂Cl₂,” Preprint at https://arxiv.org/abs/2008.06516.

Zoom: https://harvard.zoom.us/j/977347126