Particle physics in a superconductor

Abstract

The recent discovery of the Higgs boson has created a lot of excitement among scientists. Celebrated as one of the most fundamental results in experimental physics (1), the observation of this particle confirms the existence of the associated Higgs field that plays a pivotal role in the Standard Model of particle physics. Because of the Higgs boson's large mass (about 125 GeV), it could be detected only in the world's largest and most powerful accelerator—the Large Hadron Collider at CERN, Geneva. Although it sounds strange, the theoretical proposal of the Higgs mechanism was actually inspired by ideas from condensed matter physics, which typically works at much lower energies (a few electron volts or less). In 1958, Anderson discussed the appearance of a coherent excited state in superconducting condensates with spontaneously broken symmetry (2). Later, this approach was advanced by Nambu (3). The existence of superconducting condensates has been firmly established. In contrast, unambiguous experimental evidence for the coherent excited state (called the Higgs mode) had been missing. On page 1145 of this issue, Matsunaga et al. (4) report direct observation of the Higgs mode in the conventional superconductor niobium nitride (NbN) excited by intense electric field transients.