Symmetries of the Kondo gap and excitations within the hidden order state of URu2Si2

Datum

08.03.2017

Zeit

09:00 - 10:30

Sprecher

Dr. Jonathan Buhot

Zugehörigkeit

Radboud University, Nijmegen, The Netherlands

Sprache

en

Hauptthema

Materialien

Andere Themen

Chemie, Physik, Materialien

Host

Prof. Dr. L.H. Tjeng, Dr. A. Severing

Beschreibung

For three decades, the identity of the ordered phase, the so-called hidden order (HO), found in URu2Si2 at temperature below T0 = 17.5 K has eluded researchers despite intense experimental and theoretical investigations. Using Raman spectroscopy, we address here the question of the symmetries of both the novel excitations emerging from the HO state as well as the Kondo gap opening below ̴ 100 K, crucial information to solve the long-standing question of the microscopic nature of the hidden order. Polarized electronic Raman scattering were performed on URu2Si2 single crystals from 320 K to 8 K in order to explore both the Kondo liquid regime below ̴100 K and the enigmatic hidden order state below 17.5 K. The hidden order state is characterized by a sharp excitation at 1.7 meV and a gap in the electronic continuum below 6.8 meV. Both Raman signatures are of pure A2g symmetry. By comparing the behavior of the sharp Raman excitation and the neutron resonance at Q0 = (0, 0, 1), we provide new evidence, constrained by selection rules of the two probes, that the hidden order state breaks translational symmetry along the c-axis resulting in a folding of the Brillouin zone. The crossover to the Kondo coherent regime is identified through a gap - only in the Eg symmetry - that develops smoothly over a broad temperature range (70 – 120 K). Moreover, the electronic continuum in both Eg and A1g symmetries shows a linear depletion from at least 320 K. The origin of this depletion remains open. No depletion is observed in other symmetries, revealing a strong Kondo anisotropy in k-space. In the Eg symmetry, we report also the presence of a large excitation at 100 meV that we have assigned to a crystal electric field excitation on the Uranium site. In the light of these results, we will discuss the possible symmetries of the f electron ground state and excited states within the hidden order. J. Buhot et al., Phys. Rev. Lett. 113 266405 (2014) J. Buhot et al., Physica B: Condensed Matter, 10.1016/j.physb.2016.10.034 (2016)

Links

• MPI CPfS

Letztmalig verändert: 08.03.2017, 08:41:37