ELFT HÍRADÓ

[tcsaba <tcsaba AT eik.bme.hu>]

                 M E G H Í V Ó - I N V I T A T I O N

    Seminar Series of the Department of Theoretical Physics at the
           Budapest University of Technology and Economics


                       Guo-qing Zheng

         (Department of Physics, Okayama University, Japan, and
   Institute of Physics, Chinese Academy of Sciences, Beijing, China)

        Quest for topological superconductivity

Topological Insulators (TIs) are materials in which the bulk is 
insulating but the surface hosts metallic states due to non-zero 
topological invariants of the bulk band structure. A topological 
superconductor is analogous to a TI in that the superconducting gap 
function has a nontrivial topological invariant. Although a great 
success has been achieved in the study of topological insulators, 
progress in establishing bulk topological superconductivity has been 
slow until recently. In this talk, I will introduce our efforts in the 
quest of topological superconductivity in doped topological insulators 
CuxBi2Se3 [1] and Sn1-xInxTe [2,3], as well as in strongly 
electron-correlated superconductor Rb2Cr3As3 [4].
In Cu0.3Bi2Se3,  our 77Se nuclear magnetic resonance measurements showed 
that spin rotation symmetry is spontaneously broken in the hexagonal 
plane below the superconducting transition temperature Tc=3.4 K [1]. 
This is the first evidence for such symmetry breaking found in any 
superconductors. Our results not only establish spin-triplet (odd 
parity) superconductivity in this compound, but also show that it is a 
topological superconductor belonging to DIII class. We will also report 
the doping mechanism and superconductivity in Sn1-xInxTe [2,3]. In 
Rb2Cr3As3  (Tc=4.8 K ), we found strong ferromagnetic spin fluctuations 
in the normal state and point nodes in the superconducting gap [4], 
which suggest that this compound is a solid-state analogue of superfluid 
3He.

[1] K. Matano, M. Kriener, K. Segawa, Y. Ando and G.-q.Zheng, Nature 
Physics 12, 852 (2016).
[2] S. Maeda, S. Katsube, and G.-q.Zheng, J. Phys. Soc. Jpn. 86, 024702 
(2017)
[3] S. Maeda, et al, in preparation.
[4] J. Yang, Z. T. Tang, G. H. Cao and G.-q.Zheng, PRL 115, 147002 
(2015).


Időpont: 2017. május 5. péntek, 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba