University of California San Diego
报告人简历：2004-2008，复旦大学物理学士。2008-2014，爱荷华州立大学，物理学博士，师从Paul Canfield教授。2014-2017，加州大学圣地亚哥分校，物理学博士后，师从Brian Maple教授。研究方向为强关联电子体系的晶体生长、超导和磁性研究。
摘要：The search for the order parameter of the hidden order (HO) phase in URu2Si2 has attracted an enormous amount of attention for the past three decades. The small antiferromagnetic moment of only ~0.03 μB/U found in the HO phase is too small to account for the entropy of ~0.2Rln(2) derived from the second order mean field BCS-like specific heat anomaly associated with the HO transition that occurs below To = 17.5 K. A first order transition from the HO phase to a large moment antiferromagnetic (LMAFM) phase occurs under pressure at a critical pressure Pc that lies in the range 0.5 – 1.5 GPa. Many studies suggest that the HO and LMAFM phases are intimately related and that a comprehensive investigation of both phases will be useful in unraveling the nature of order parameter of the HO phase. We have recently demonstrated that tuning URu2Si2 by substitution of Fe for Ru offers an opportunity to study the HO and LMAFM phases at atmospheric pressure. Specifically, the substitution of the smaller Fe ions for Ru ions in URu2Si2 acts as a "chemical pressure" and reproduces the temperature vs applied pressure phase diagram as demonstrated by measurements of the electrical resistivity, specific heat, and magnetization of the URu2-xFexSi2 system. We have performed neutron diffraction measurements on single crystal samples of URu2-xFexSi2 for various values of x which show that the magnetic moment increases abruptly to a maximum value at x ≈ 0.2 above which it then decreases slowly with x, supporting the interpretation that tuning by Fe substitution acts as chemical pressure. Therefore, our results provide a unique opportunity to carry out ambient pressure experiments to study the LMAFM phase that was known to exist under high pressure. Motivated by this observation, we performed thermal expansion measurements, as well as electrical resistivity measurements in high magnetic fields, on URu2-xFexSi2 single crystals for various values of x in both the HO and LMAFM regions of the phase diagram. Interesting preliminary results have emerged from these studies that shed light on the LMAFM phase and its relationship with the elusive HO phase.
1. Sheng Ran, Christian T. Wolowiec, Inho Jeon, Naveen Pouse, Noravee Kanchanavatee, Benjamin D. White, Kevin Huang, Dinesh Martien, Tyler DaPron, David Snow, Mark Williamsen, Stefano Spagna, Peter S. Riseborough, and M. Brian Maple, "Phase diagram and thermal expansion measurements on the system URu2-xFexSi2", Proc. Natl. Acad. Sci., 113, 13348-13353 (2016).
2. Sheng Ran, Inho Jeon, Naveen Pouse, Alexander J. Breindel, Noravee Kanchanavatee, Kevin Huang, Andrew Gallagher, Kuan-Wen Chen, David Graf, Ryan E. Baumbach, John Singleton, and M. Brian Maple, "Phase diagram of URu2-xFexSi2 in high magnetic fields", Proc. Natl. Acad. Sci., published ahead of print August 28, (2017).