Northwestern Events Calendar

Oct
31
2019

CMP Seminar: Dr. Joshua Wiman: New approaches to the conventional Higgs mode

When: Thursday, October 31, 2019
4:00 PM - 5:30 PM Central

Where: Technological Institute, F160, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students

Contact: Cristian Pennington  

Group: Physics and Astronomy Condensed Matter Physics Seminars

Category: Academic

Description:

The collective modes of superconductors draw considerable interest as they are fundamental products of spontaneous symmetry breaking and the superconducting state. The amplitude mode, or Higgs mode, lies at the gap energy of $2\Delta$ and is therefore a potential tool for  directly probing the underlying condensate. Actually detecting the Higgs mode, however, proves to be difficult. It does not couple to the EM field at first order, and exciting it typically involves a strong pairbreaking pulse. Recently, Moor, Volkov, and Efetov[1] have noted that an applied DC supercurrent bias allows the Higgs mode to couple to an EM field in the linear response regime. Following them, Nakamura et al[2] have claimed experimental detection of the Higgs mode in NbN using this technique. We consider this problem in quasiclassical Keldysh theory across a range of applied supercurrent and impurity strengths to see whether the Higgs mode can plausibly be recovered in the optical conductivity response of the superconductor.

[1] A. Moor, A. F. Volkov, and K. B. Efetov. Amplitude Higgs mode and admittance in superconductors with a moving condensate. Phys. Rev. Lett. 118, 047001 (2017). 
[2] S. Nakamura, Y. Iida, Y. Murotani, R. Matsunaga, H. Terai, and R. Shimano. Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN. Phys. Rev. Lett. 122, 257001 (2019).

Dr. Joshua Wiman, Chalmers University

Host: James Sauls

Keywords: Physics, Astronomy, Condensed Matter

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