One of the most remarkable phenomena in condensed matter science is the sudden, total disappearance of electrical resistance of many metals, alloys, and compounds as the temperature is lowered through a material-specific critical temperature (TC). Currently, cuprate and iron-based systems were recognized as the two systems having high-Tc superconductivity. Pressure plays an essential role in inducing or tuning superconductivity as well as shedding insight on the mechanism of superconductivity in unconventional superconductors. Finding ways to control the quantum coherence properties to have a higher critical temperature TC than the material has remains a challenge. There has not been an agreement regarding the underlying mechanism of high temperature superconductivity. Here I would like to talk about our efforts in exploring superconductivity in both directions. I will show how to enhance remarkably Tc through the pressure tuning of competing electronic order in cuprates[1] and how to use the electronic Raman spectra to identify the mechanism of superconductivity in high-Tc cuprates[2]. I also will introduce ordering tuning of superconductivity in two distinct regimes in newly discovered iron-based superconductors[3,4]. Our results have important implications for designing and engineering superconductors with much higher TC’s at ambient conditions.
[1] X. J. Chen, V. V. Struzhkin, Y. Yu, A. F. Goncharov, C. T. Lin, H. K. Mao, and R. J. Hemley, Nature 466, 950-953 (2010).
[2] X. J. Chen, J. X. Zhu, A. F. Goncharov, V. V. Struzhkin, J. S. Wen, Z. J. Xu, G. D. Gu, C. T. Lin, R. J. Hemley, and H. K. Mao, Distinguishing underlying mechanisms of superconductivity in cuprates (2012).
[3] L. L. Sun*, X. J. Chen*, J. Guo, P. W. Gao, H. D. Wang, M. H. Fang, X. L. Chen, G. F. Chen, Q. Wu, C. Zhang, D. C. Gu, X. L. Dong, K. Yang, A. G. Li, X. Dai, H. K. Mao, and Z. X. Zhao, Nature 483, 67-69 (2012) (*equal contribution).
[4] X. J. Chen, Q. Huang, S. B. Wang, J. X. Zhu, W. Bao, M. H. Fang, J. B. Zhang, L. Y. Tang, Y. M. Xiao, P. Chaw, J. Shu, W. L. Mao, V. V. Struzhkin, R. J. Hemley, and H. K. Mao, Ordering modulation of superconductivity in an alkaline iron selenide (2012).
