Effect of C additives with 0.5% in weight on structural, optical and superconducting properties of Ta-Nb-Hf-Zr-Ti high entropy alloy films

Tien Le; Yeonkyu Lee; Dzung T. Tran; Woo Seok Choi; Won Nam Kang; Jinyoung Yun; Jeehoon Kim; Jaegu Song; Yoonseok Han; Tuson Park; Duc H. Tran; Soon-Gil Jung; Jungseek Hwang

arXiv · 2509.20650

Effect of C additives with 0.5% in weight on structural, optical and superconducting properties of Ta-Nb-Hf-Zr-Ti high entropy alloy films

Tien Le·Yeonkyu Lee·Dzung T. Tran·Woo Seok Choi·Won Nam Kang·Jinyoung Yun·Jeehoon Kim·Jaegu Song·Yoonseok Han·Tuson Park·Duc H. Tran·Soon-Gil Jung·Jungseek Hwang

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Abstract

We investigated the superconducting (SC) properties of Ta-Nb-Hf-Zr-Ti high-entropy alloy (HEA) thin films with 0.5% weight C additives. The C additives stabilize the structural properties and enhance the SC critical properties, including $\mu_0$Hc$_2$ (13.45 T) and Tc (7.5 K). The reflectance of the C-added HEA film is enhanced in the low-energy region, resulting in a higher optical conductivity, which is consistent with the lower electrical resistivity. In addition, we observed SC vortices in the C-added HEA film using magnetic force microscopy. The magnetic penetration depths ($\lambda$) of the pure HEA and C-added HEA films were estimated from their Meissner force curves by comparing them with those of a reference Nb film. At 4.2 K, the {\lambda} of the C-added film is 360 nm, shorter than that of the pure HEA film (560 nm), indicating stronger superconductivity against an applied magnetic field.

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Tien Le, Yeonkyu Lee, Dzung T. Tran, Woo Seok Choi, Won Nam Kang, Jinyoung Yun, Jeehoon Kim, Jaegu Song, Yoonseok Han, Tuson Park, Duc H. Tran, Soon-Gil Jung, Jungseek Hwang. 2025-09-25. Effect of C additives with 0.5% in weight on structural, optical and superconducting properties of Ta-Nb-Hf-Zr-Ti high entropy alloy films. https://arxiv.org/abs/2509.20650

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