Related papers: Hybridization gap versus hidden order gap in URu$_…
We summarize existing optical data of URu$_2$Si$_2$ to clarify the nature of the hidden order transition in this heavy fermion metal. Hybridization develops between 50 K and 17.5 K, and a coherent Drude peak emerges which mirrors the…
We present a detailed temperature and frequency dependence of the optical conductivity measured on clean high quality single crystals of URu$_{2}$Si$_{2}$ of $ac$- and $ab$-plane surfaces. Our data demonstrate the itinerant character of the…
We measured the polarized optical conductivity of URu$_2$Si$_2$ from room temperature down to 5 K, covering the Kondo state, the coherent Kondo liquid regime, and the hidden-order phase. The normal state is characterized by an anisotropic…
We performed far-infrared optical spectroscopy measurements on the heavy fermion compound URu 2 Si 2 as a function of temperature. The light's electric-field was applied along the a-axis or the c-axis of the tetragonal structure. We show…
A phenomenological model for the 'hidden order' transition in the heavy Fermion material URu$_2$Si$_2$ is introduced. The 'hidden order' is identified as an incommensurate, momentum-carrying hybridization between the light hole band and the…
We address two long-standing questions regarding the hidden order in URu2Si2: Is it associated with the hybridization process, and what are the distinct roles played by the localized and itinerant electrons? Our quasiparticle scattering…
The nature of the second order phase transition that occurs in URu2Si2 at 17.5 K remains puzzling despite intensive research over the past two and half decades. A key question emerging in the field is whether a hybridization gap between the…
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.…
Through an analysis and modeling of data from various experimental techniques, we present clear evidence for the presence of a hidden order pseudogap in \U in the temperature range between 25 K and 17.5 K. Considering fluctuations of the…
Temperature-dependent reflectivity measurements in the frequency range 85 - 7000 cm$^{-1}$ were performed on BaFe$_2$As$_2$ single crystals under pressure up to $\sim$5 GPa. The corresponding pressure- and temperature-dependent optical…
We study, using high-resolution angle-resolved photoemission spectroscopy, the evolution of the electronic structure in URu2Si2 at the Gamma, Z and X high-symmetry points from the high-temperature Kondo-screened regime to the…
The detailed optical properties have been determined for the iron-based materials $A$Fe$_2$As$_2$, where $A=\,$Ca, Sr, and Ba, for light polarized in the iron-arsenic ($a-b$) planes over a wide frequency range, above and below the magnetic…
URu2Si2 presents superconductivity at temperatures below 1.5 K, and a hidden order (HO) at about 17.5 K, both electronic phenomena are in uenced by Fano and Kondo resonances. At 17.5 K the HO was related in the past to a Peierls distortion…
We perform an in-plane optical spectroscopy measurement on high quality FeSe single crystals grown by a vapor transport technique. Below the structural transition at $T_{\rm s}\sim$90 K, the reflectivity spectrum clearly shows a gradual…
We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd$_2$Al$_3$: conductance spectra are taken from single crystals with two major surface orientations as a function of temperature and…
A dramatic increase in the total thermal conductivity (k) is observed in the Hidden Order (HO) state of single crystal URu2Si2. Through measurements of the thermal Hall conductivity, we explicitly show that the electronic contribution to k…
Using a large-N approach, we demonstrate that the differential conductance and quasi-particle interference pattern measured in recent scanning tunneling spectroscopy experiments (A.R. Schmidt et al. Nature 465, 570 (2010); P. Aynajian et…
In this article we present high-resolution angle-resolved photoemission (ARPES) spectra of the heavy-fermion superconductor URu$_2$Si$_2$. Measurements as a function of both excitation energy and temperature allow us to disentangle a…
The hidden order developing below 17.5K in the heavy fermion material URu2Si2 has eluded identification for over twenty five years. This paper will review the recent theory of ``hastatic order,'' a novel two-component order parameter…
Hidden order in URu$_2$Si$_2$ has remained a mystery now entering its 4th decade. The importance of resolving the nature of the hidden order has stimulated extensive research. Here we present a detailed characterization of different surface…