Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN

Sachiko Nakamura, Yudai Iida, Yuta Murotani, Ryusuke Matsunaga, Hirotaka Terai, Ryo Shimano

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

The Higgs mode in superconductors, i.e., the collective amplitude mode of the order parameter, does not associate with charge nor spin fluctuations, therefore it does not couple to the electromagnetic field in the linear response regime. Contrary to this common understanding, here, we demonstrate that if the dc supercurrent is introduced into the superconductor, the Higgs mode becomes infrared active and is directly observed in the linear optical conductivity measurement. We observed a sharp resonant peak at ω=2Δ in the optical conductivity spectrum of a thin-film NbN in the presence of dc supercurrent, showing a reasonable agreement with the recent theoretical prediction. The method as proven by this work opens a new pathway to study the Higgs mode in a wide variety of superconductors.

Original languageEnglish
Article number257001
JournalPhysical review letters
Volume122
Issue number25
DOIs
Publication statusPublished - Jun 25 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

Fingerprint

Dive into the research topics of 'Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN'. Together they form a unique fingerprint.

Cite this