摘要

Strongly correlated electron systems, displaying heavy fermion (HF) behaviour, have attracted considerable attention both in theoretical and experimental condensed matter physics due to the many exotic properties they can exhibit. One of the most attractive and elusive phenomena of these HF systems is the coexistence of magnetism and superconductivity (SC), which is at the forefront of condensed matter research. Recently there has been considerable interest in studying non-centrosymmetric superconductors (NCS) due to possibility of the gap function being a mixture of spin singlet and triplet states. In particular there have been many studies looking for pressure induced unconventional superconductivity in NCS HF systems, which have strong competition between onsite Kondo effect and intersite RKKY interactions. As a result they exhibit many complex magnetic and superconducting properties, for example multiple magnetic phase transitions with the ordered state moments do not align along the easy axis of the single ion anisotropy, commensurate to incommensurate magnetic transition as well as superconductivity accompanied with a non-Fermi liquid behaviour.

Recently, we have been investigating the physical properties of non-centrosymmetric CeTX3 (T = transition metal, X = Si, Ge, Sn, Al) compounds using μSR and neutron scattering techniques, which exhibit complex magnetic properties [1-4]. In the present talk I will discuss our recent results of neutron scattering (both elastic and inelastic) and μSR on CeIrGe3, which exhibits multiple magnetic phase transitions (TN1=8.5 K, TN2=6.0 K, TN3=4.6 K) and pressure induced superconductivity with Tc=1.5 K above 22 GPa [4]. Our powder neutron diffraction (ND) data reveal an incommensurate magnetic structure with propagation vector k = (0,0,0.688) below TN1 which then locks to the commensurate propagation vector k = (0, 0, 2/3) in the ground state. The commensurate magnetic phase, taking place at TN3, couples a macroscopic ferromagnetic component and can be induced by external magnetic field above this temperature. This results in experimentally observed metamagnetic behaviour and implies magnetic-field induced lock-in transition. The single-ion CEF anisotropy predicts the moment direction in the ab-plane, but the moment direction observed from the ND is along the c-axis, indicating that anisotropic magnetic exchange interactions or transverse fluctuations are important for the observed unconventional moment direction. I will compare the present results with other CeTX3 compounds and give a brief overview of µSR and neutron scattering techniques.

[1] V. K. Anand, D. T. Adroja, D. Britz, A. M. Strydom, J. W. Taylor, and W. Kockelmann, Phys. Rev. B 94, 014440 (2016)

[2] A. D. Hillier, D. T. Adroja, P. Manuel, V. K. Anand, J. W. Taylor,K. A. McEwen, B. D. Rainford, and M. M. Koza, Phys. Rev. B 85, 134405 (2012)

[3] D. T.  Adroja, A. del Moral, C. de la Fuente, A. Fraile, E. A. Goremychkin, J. W. Taylor, A. D. Hillier, and F. Fernandez Alonso, Phys. Rev. Lett. 108, 216402 (2012)

[4] V. K. Anand, A. D. Hillier, D. T. Adroja, D. D. Khalyavin, P. Manuel, G. Andre, S. Rols and M. M. Koza, Phys. Rev. B 97, 184422 (2018)

报告人简介

Devashibhai Adroja is a senior scientist and STFC Fellow at the ISIS facility, Rutherford Appleton Laboratory, UK, and is responsible for the time of flight spectrometer MERLI. He is also a visiting professor at Johannesburg University, South Africa. Dr Adroja obtained his PhD degree in 1991 from Indian Institute of Technology, Bombay, India and then worked as a research fellow at Southampton, JSPS fellowship at Hiroshima University, research fellow at St Andrews before joining ISIS facility in 1999. His research programme is focused on strongly correlated electron systems, with a special emphasis on quantum criticality and non-Fermi-liquid behaviour, low-D and frustrated magnetism, heavy fermion superconductivity, high temperature superconductors, FeAs-based and Cr-based superconductors and caged type thermoelectric materials. He is an acknowledged expert on the magnetism of f-electron systems and he has more than 28 years of experience in neutron scattering and muon spin rotation techniques. He was the pioneer in discovering the Kondo insulator beaviour in CeRhSb. Recently he has made significant contributions to the field of spin, charge gap formation in strongly correlated electron systems and Fe- and Cr-based superconductors, and published three review papers on these topics. He has published over 300 papers in peer-review journals.