Anisotropy of point-contact characteristics of URu2Si2 in the normal state

Differential resistance dV/dI(V) of point contacts based on the heavy-fermion compound (HFC) URu2Si2 is measured in the temperature range 1.5–20 K along two principal crystallographic directions. A distinguishing feature of dV/dI(V) measured below the Néel temperature TN = 17.5 K for URu2Si2 point contacts is a peak located asymmetrically with respect to zero voltage (V = 0). On the symmetric part of the dependence dV/dI(V) for homojunctions, such a peak is observed for currents directed at right angles to the c-axis, while the peak is suppressed or missing along the c-axis. The existence of such a peak is associated with anisotropic energy gap in the ab-plane, which is attributed to the spin-density waves (SDW) and appears on a part of the Fermi surface at temperatures below TN. The magnitude of the gap, estimated from the width of the peak in the symmetric part of dV/dI(V) for V = 0, was found to be equal to 10±l mV. The reproducible asymmetry of the differential resistance of heterojunctions between URu2Si2 and simple metals is studied and attributed to the effect of the peak of the high-density electron states, located asymmetrically with respect to the Fermi level in the HFC.

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