Observation of Multiple-Gap Structure in Hidden Order State of URu2Si2 from Optical Conductivity

Abstract

We have measured the far infrared reflectance of the heavy fermion compound URu${}_2$Si${}_2$ through the phase transition at T${}_{HO}$=17.5 K dubbed 'hidden order' with light polarized along both the a- and c-axes of the tetragonal structure. The optical conductivity allows the formation of the hidden order gap to be investigated in detail. We find that both the conductivity and the gap structure are anisotropic, and that the c-axis conductivity shows evidence for a double gap structure, with ${\Delta }_{1,c}=2.7$ meV and ${\Delta }_{2,c}=1.8$ meV respectively at 4 K, while the gap seen in the a-axis conductivity has a value of ${\Delta }_a=3.2$ meV at 4 K. The opening of the gaps does not follow the behaviour expected from mean field theory in the vicinity of the transition.

6 pages, 5 figures

References in corpus (4)

• Imaging the Fano Lattice to 'Hidden Order' Transition in URu2Si2
• Rotational Symmetry Breaking in the Hidden-Order Phase of URu2Si2
• Gapped itinerant spin excitations account for missing entropy in the hidden order state of URu${}_2$Si${}_2$
• Fermi surface instability at the hidden-order transition of URu2Si2

Cited by in corpus (8)

• Chirality density wave of the 'hidden order' phase in URu${}_2$Si${}_2$
• Hidden Order Behaviour in URu2Si2 (A Critical Review of the Status of Hidden Order in 2014)
• Momentum-resolved evolution of the Kondo lattice into 'hidden-order' in URu2Si2
• Symmetry of the Excitations in the Hidden Order State of URu2Si2
• Analogy between the "Hidden Order" and the Orbital Antiferromagnetism in URu${}_{2-x}$Fe${}_x$Si${}_2$
• Detailed optical spectroscopy of the hybridization gap and the hidden order transition in high quality URu${}_2$Si${}_2$ single crystals
• Optical study of hybridization and hidden order in URu${}_2$Si${}_2$
• Quasiparticle Relaxation Dynamics in URu${}_{2-x}$Fe${}_x$Si${}_2$ Single Crystals