- Hironori Sakai: Anisotropic antiferromagnetic spin fluctuations near the quantum critical point of Ising-type antiferromagnet CeRh2Si2
- 15. 10. 2014, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
The need to determine the nature of spin fluctuations and their possible relationship to unconventional superconductivity in heavy fermion systems has posed a long-standing problem. The heavy fermion superconductors CeCoIn5 (Tc = 2.3 K) and PuCoGa5 (Tc=18.5 K) provide interesting case studies for this problem. Both compounds can be classified as members of a 115 family with the layered HoCoGa5-type crystal structure. Systematic NMR investigations [1-4] have suggested that XY-type antiferromagnetic (AFM) spin fluctuations are favorable for d-wave superconductivity in 115 compounds. Recently, this working hypothesis is now being examined in several other systems. In this talk, the relation of superconducting TC and the anisotropy of AFM spin fluctuations will be summarized briefly, and the results in an Ising-type antiferromagnet CeRh2Si2 will be presented.
Heavy fermion antiferromagnet CeRh2Si2 shows the successive AFM transitions at TN1=36 K and TN2=25 K, which are suppressed by pressures [5]. The quantum critical point (QCP) by pressure is estimated to be P~1 GPa and the superconductivity is also found near the QCP [6-8]. Indeed, in the paramagnetic (PM) state of CeRh2Si2 under ambient pressure, Ising-type AFM spin fluctuations are confirmed by means of our NMR result. By applying pressures, the anisotropy of AFM spin fluctuations in the PM state is found to change to XY-type AFM fluctuations near QCP.
References
1) S. Kambe et al., Phys. Rev. B 75, 140509(R) (2007).
2) H. Sakai et al., in: “Basic Actinide Science and Materials for Nuclear Applications” (Mater. Res. Soc. Symp. Proc., 2010) p. 1264.
3) S.-H. Baek et al., Phys. Rev. Lett. 105, 217002 (2010).
4) H. Sakai et al., Phys. Rev. Lett. 107, 137001 (2011).
5) S. Kawarazaki et al., Phys. Rev. B 61, 4167 (2000).
6) R. Movshovich et al, Phys. Rev. B 53, 8241 (1996).
7) T. C. Kobayashi et al, Physica B 281-282, 7 (2000).
8) S. Araki et al, J. Phys. :Condens. Matter 14, L377 (2002).