Signature of hidden order and evidence for periodicity modification in ${\text{URu}}_2{\text{Si}}_2$

The detail of electronic structures near the Fermi level in ${\text{URu}}_2{\text{Si}}_2$ has been investigated employing state-of-art laser angle-resolved photoemission spectroscopy. The observation of a narrow dispersive band near the Fermi level in the ordered state as well as its absence in a Rh-substituted sample strongly suggest that the emergence of the narrow band is a clear signature of the hidden-order transition. The temperature dependence of the narrow band, which appears at the onset of the hidden-order transition, invokes the occurrence of periodicity modification in the ordered state, which is shown for the first time by any spectroscopic probe. We compare our data to other previous studies and discuss possible implications.

Figure 1

(Color online) Wide scan measured at 25 K for [100] direction: (left panel) ARPES intensity plot, (right panel) corresponding energy-distribution curves. In the right panel, the bold curve corresponds to the cut at $0{\text{Å}}^{-1}$, and the broken lines are guide for the eyes. The maxima of a concave-up dispersive band is clearly seen at around $E_{\text{B}}\sim 300\text{meV}$.

Figure 2

(Color online) Laser ARPES data obtained at 7 K for ${\text{URu}}_2{\text{Si}}_2$ (a) ARPES intensity plot for [110] direction and (b) for [100] direction, (c) energy-distribution curves, and (d) momentum- distribution curves for [110] direction. The bold curves in (c) corresponds to the spectra at $k_{\text{F}}$, and the broken lines in (d) are guide for the eyes.

Figure 3

(Color online) Intensity mapping at $E_{\text{F}}$ performed for ${\text{URu}}_2{\text{Si}}_2$ at 25 K. Positions of $k_{\text{F}}$ obtained from MDC analysis are also plotted for three data sets. Note that fitting data have been fourfold symmetrized.

Figure 4

(Color online) ARPES intensity plots for $\text{U}{\left({\text{Ru}}_{1-x}{\text{Rh}}_x\right)}_2{\text{Si}}_2\left(x\sim 0.03\right)$ measured for [100] direction with $s$-polarized light (a) at 7 K and (b) at 26 K. Momentum- distribution curves taken at 26 K are shown in Fig. 4c and describes the existence of a holelike dispersive band. Note that the broken lines in (c) are guide for the eyes. Figure 4d shows EDCs taken at $k_{\parallel }=0.14{\text{Å}}^{-1}$. EDCs are normalized to the area.

Figure 5

(Color online) [(a)–(g)] Temperature evolution of ARPES intensity plots for ${\text{URu}}_2{\text{Si}}_2$ measured along [100] over the temperature range of 7–25 K, (h) EDCs for the above data taken at $k_{\parallel }=0{\text{Å}}^{-1}$ (cut A) and (i) EDCs at $k_{\parallel }=-0.12{\text{Å}}^{-1}$ (cut B). (j) angle-integrated spectra for [100] ARPES intensity plots, and (k) angle-integrated spectra for [110] ARPES intensity plots obtained with $s$ polarization. Note that spectra are normalized by the intensity at $E_{\text{B}}=12\text{meV}$.