Z. Q. Mao
Department of Physics and Engineering Physics, Tulane University

日期：6月26日（周四）上午 10:30
地点：唐仲英楼B501

摘要：
The interplay between magnetism and superconductivity in Fe-based superconductor systems is currently a subject of intense studies. The iron chalcogenide Fe1+y(Te1-xSex) is of particular interest due to its unique magnetic properties. While the parent compound Fe1+yTe shows antiferromagnetism with (,0) in-plane magnetic wave vector [1], the optimally doped sample displays superconductivity with (p,p) spin resonance [2]. This contrasts with iron pnictides in which both the parent compound's antiferromagnetism [3-4] and the doped samples' superconducting (SC) spin resonance [5-7] are characterized by the in-plane Fermi surface nesting wave vector Qn = (p,p). The evolution from (,0) magnetism to superconductivity with (,) spin resonance in iron chalcogenides is associated with coexistence of magnetic correlations at (,0) and (,) [8]. The other remarkable difference between iron chalcogenide and iron pnictide superconductors is their phase diagrams. In iron pnictides, bulk superconductivity either emerges immediately following suppression of long-range (p,p) antiferromagnetic (AFM) order [9-10], or coexists with it in a particular composition range [11-14]. In contrast, in iron chalcogenides, bulk superconductivity does not appear immediately following the suppression of long-range (p,0) AFM order. Instead, an intermediate phase with weak charge carrier localization appears between AFM order and bulk superconductivity for 0.09 < x < 0.3 [8]. In this talk, I will first present an overview on the results summarized above and then introduce our recent studies on the coupling between electronic and magnetic properties in this system [8,15]. I will show the doping dependences of Sommerfeld coefficient , Hall coefficient RH and Hall angle as well as their relations with superconductivity [15]. The origin of superconductivity suppression and charge carrier localization in the underdoped region will be discussed in terms of these experimental results.
References:
[1] W. Bao et al., Phys. Rev. Lett 102, 247001 (2009).
[2] Y. Qiu et al., Phys. Rev. Lett 103, 067008 (2009).
[3] C. de la Cruz et al., Nature 453, 899 (2008).
[4] Q. Huang et al., Phys. Rev. Lett 101, 257003 (2008).
[5] A. D. Christianson et al., Nature 456, 930 (2008).
[6] M. D. Lumsden et al., Phys. Rev. Lett 102, 107005 (2009).
[7] S. Chi et al., Phys. Rev. Lett 102, 107006 (2009).
[8] T. J. Liu et al., Nat. Mater. 9, 718 (2010).
[9] J. Zhao et al., Nat. Mater. 7, 953 (2008).
[10] H. Luetkens et al., Nat. Mater. 8, 305 (2009).
[11] A. J. Drew et al., Nat. Mater. 8, 310 (2009).
[12] H. Chen et al., Europhys. Lett. 85, 17006 (2009).
[13] J.-H. Chu et al., Phys. Rev. B 79, 014506 (2009).
[14] S. Nandi et al., Phys. Rev. Lett 104, 057006 (2010).
[15] J. Hu et al., Phys. Rev. B 88, 094505 (2013).

报告人简介：毛志强，1987年毕业于南京师范大学获得学士学位，1992年于中国科学技术大学获得物理学博士学位后留校工作。1997年到2002年先后在日本京都大学和美国宾州州立大学从事博士后研究。2002年加入杜兰大学物理系。 现为杜兰大学物理系主任，Nicholas J. Altiero 名誉教授。他的研究领域主要包括强关联体系钙钛矿结构钌氧化物的奇异量子效应以及铁基超导体。发表包括Nature, Science, Nature materials, PRL 等重要文章234篇，H因子36。毛志强教授2005年获Tulane大学校长奖（此奖授予每年度最杰出的在Tulane大学工作的青年学者，每年度仅一名），同年获美国Research Corporation基金会Cottrell学者奖（全美每年13人），2007年获美国自然科学基金委员会Career奖。2011年获得Nicholas J. Altiero荣誉教授。