Description:

Abstract:

In this talk, we will present our recent study of electromagnetic responses in 3D topological superconductors and Weyl superconductors originating from Majorana surface states. In the first part, we will discuss the temperature dependence of the penetration depth in a 3D topological superconductor (TSC), incorporating the paramagnetic current due to the Majorana surface state [1]. We consider “solid-state 3He-B” (a class DIII p-wave TSC) and compute its response to an external magnetic field. Interestingly, our calculation shows that there is a  non-trivial T^3 power law temperature dependence of the penetration depth due to the surface states in the low temperature limit. Our system is fully gapped in the bulk, and our result should be compared to bulk nodal superconductivity, which also exhibits power-law behavior. Our results imply that power-law temperature dependence of the penetration depth can be one indicator of topological superconductivity, in addition to the standard one-particle probes (STM, ARPES).
 
In the second part, we will discuss the optical absorption in a 3D Weyl superconductor (WSC) due to transitions between the surface and bulk states [2]. For concreteness, we consider “solid-state 3He-A” (a class D p_x + ip_y single band WSC) which possesses chiral Majorana surface states. In the clean limit, the optical absorption purely from the bulk or purely from the surface is vanishing. The only non-trivial response is from the surface-bulk transition which gives rise to a characteristic absorption peak. We close by briefly discussing the effect of disorder on the response. Our results are relevant for the recently proposed chiral superconductor candidate UTe2 .

[1] T.C. Wu, H.K. Pal, P. Hosur, M.S. Foster, “Power-Law Temperature Dependence of the
Penetration Depth in a Topological Superconductor Due to Surface States”, Phys. Rev. Lett.
124, 067001 (2020).
[2] Tsz Chun Wu, Hridis K. Pal, and Matthew S. Foster, “Topological anomalous skin effect in
Weyl superconductors”, Phys. Rev. B 103, 104517 (2021).

Speaker: Dr. Tsz Chun Wu, Rice University 

Host: Professor James Sauls