# Point-contact spectroscopy of superconducting energy gap in $\rm DyNi_2B_2C$

## TL;DR

This study investigates the superconducting energy gap in DyNi2B2C using point-contact spectroscopy and finds that the gap properties are consistent with BCS theory but are influenced by magnetic order and surface conditions.

## Contribution

First application of point-contact spectroscopy to measure the superconducting gap in DyNi2B2C, revealing magnetic effects on the gap structure.

## Key findings

- The superconducting gap ratio 2Δ₀/kBTc ≈ 3.63, consistent with BCS theory.
- Superconducting gap features are suppressed by magnetic fields around 3T.
- Surface composition and structure affect the observed superconducting properties.

## Abstract

The superconducting energy gap in $\rm DyNi_2B_2C$ has been investigated using a point-contact technique based on the Andreev reflection from a normal (N)-superconductor (S) boundary, where N is Ag. The observed differential resistance $dV/dI$ is well described by the Blonder-Tinkham-Klapwijk (BTK) theory based on the BSC density of states with zero broadening parameter. Typically, the intensity of the gap structure amounts to several percentage of the normal state resistance, which is an order of magnitude less than predicted by the theory. For $\rm DyNi_2B_2C$ with $T_c<T_N$ (the Neel temperature), we found gap values satisfying the ratio of $2\Delta_0/k_BT_c=3.63\pm 0.05$ similar to other superconducting nickel-borocarbides, both nonmagnetic and magnetic with $T_c\geq T_N$. The superconducting gap nonlinearity is superimposed on the antiferromagnetic structure in $dV/dI(V)$ which is suppressed at the magnetic field of the order of 3T applied nominally in the $ab$-plane and temperature $\geq 11~K$. The observed superconducting properties depend on the exact composition and structure at the surface of the crystal.