Suppression of asymmetric differential resistance in the non-Fermi-liquid system ${\text{YbCu}}_{5-x}{\text{Al}}_x$ $\left(x=1.3–1.75\right)$ in high magnetic fields

The non-Fermi-liquid system ${\text{YbCu}}_{5-x}{\text{Al}}_x$ $\left(x=1.3–1.75\right)$ has been investigated in heterocontact as well as homocontact arrangement in magnetic fields up to 22.5 T. The observed differential resistance $\left[dV/dI\left(V\right)\right]$ characteristics reveal asymmetry in heterocontact arrangement and do not agree with the model of thermal contact heating, at least close to zero-bias voltage. In the case of a heterocontact arrangement we have observed a maximum at only one voltage polarity at about 1.3 mV (for $x=1.5$) and this asymmetry is suppressed in an applied magnetic field. We show that such behavior is connected with the non-Fermi-liquid state of the studied system.

Figure 1

Characteristic magnetic-field behavior of $dV/dI\left(V\right)$ for heterocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}\text{-Pt}$ at 1.5 K.

Figure 2

Characteristic magnetic-field behavior of $dV/dI\left(V\right)$ for heterocontact ${\text{YbCu}}_{3.7}{\text{Al}}_{1.3}\text{-Cu}$ at 1.5 K.

Figure 3

Characteristic magnetic-field behavior of $dV/dI\left(V\right)$ for heterocontact ${\text{YbCu}}_{3.25}{\text{Al}}_{1.75}\text{-Cu}$ at 1.5 K.

Figure 4

Characteristic magnetic-field behavior of $dV/dI\left(V\right)$ for homocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}{\text{-YbCu}}_{3.5}{\text{Al}}_{1.5}$ at 1.5 K.

Figure 5

Characteristic $dV/dI\left(V\right)$ for heterocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}\text{-Pt}$ (dashed line) and homocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}{\text{-YbCu}}_{3.5}{\text{Al}}_{1.5}$ (solid line) arrangements at 1.5 K.

Figure 6

Comparison of calculated $dV/dI\left(V\right)$ curves at different temperatures (solid curves) and experimental data of homocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}{\text{-YbCu}}_{3.5}{\text{Al}}_{1.5}$ (dashed curve) at 1.5 K.

Figure 7

Characteristic temperature behavior of (a) symmetric and (b) asymmetric parts of $dV/dI\left(V\right)$ for heterocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}\text{-Cu}$ at $B=0\text{T}$. The inset shows the bulk resistivity $\rho \left(T\right)$ of ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}$ (Ref. 2).

Figure 8

Characteristic $dV/dI\left(V\right)$ of heterocontact ${\text{YbCu}}_{3.5}{\text{Al}}_{1.5}\text{-Pt}$ at 6 K (solid curve) and at 0.1 K (dashed curve).

Figure 9

Characteristic magnetic-field behavior of $dV/dI{\left(V\right)}^{as}$ for heterocontacts with different $x=1.3$, 1.5, and 1.75 at 1.5 K.