Detailed optical spectroscopy of hybridization gap and hidden-order transition in high-quality URu(2)S(i)2 single crystals

作者：Bachar N^*; Stricker D; Muleady S; Wang K; Mydosh J A; Huang Y K; van der Marel D

来源：Physical Review B, 2016, 94(23): 235101.

DOI：10.1103/PhysRevB.94.235101

We present a detailed temperature and frequency dependence of the optical conductivity measured on clean high-quality single crystals of URu2Si2 of ac- and ab-plane surfaces. Our data demonstrate the itinerant character of the narrow 5f bands, becoming progressively coherent as the temperature is lowered below a crossover temperature T* similar to 75 K. T* is higher than in previous reports as a result of a different sample preparation, which minimizes residual strain. We furthermore present the density-response (energy-loss) function of this compound, and determine the energies of the heavy-fermion plasmons with a-and c-axis polarization. Our observation of a suppression of optical conductivity below 50 meV along both the a and c axes, along with a heavy-fermion plasmon at 18 meV, points toward the emergence of a band of coherent charge carriers crossing the Fermi energy and the emergence of a hybridization gap on part of the Fermi surface. The evolution towards coherent itinerant states is accelerated below the hidden order temperature T-HO = 17.5 K. In the hidden order phase the low-frequency optical conductivity shows a single gap at similar to 6.5 meV, which closes at T-HO .

• 出版日期2016-12-1