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本文研究了两相重费米子超导体CeRh2As2在不同磁场下的电热输运行为。零场电阻率显示，CeRh2As2在临界温度Tc=0.34 K发生超导转变。在外加磁场1 T时，电阻率在T0≈0.42 K附近出现极小值，该特征可能源于费米面嵌套引发的能隙部分打开，标志着体系进入磁有序态，但在零场条件下我们没有观察到这一现象。在T0至2 K的温区，体系表现出ρ~T0.44的非费米液体行为，暗示其靠近量子临界点。当外加磁场达到7 T时，超导转变被完全压制，电阻率在低温下恢复费米液体行为。CeRh2As2的零场热导率在Tc附近未观测到显著异常，这一现象可能与样品较高的剩余电阻率以及伴随超导转变和T0相变发生的载流子浓度下降相关，需要优化样品的制备从而减小晶格缺陷或化学无序对热输运测量的影响。施加磁场后，热导率曲线相较零场小幅上移。当温度为0.15 K时，热导率随磁场增加而升高，随着外场升至5 T以上，热导率趋于饱和。在7 T的正常态，我们发现电阻率和热导率满足Wiedemann-Franz定律，表明电荷输运与热输运均由同一类准粒子主导，这与该磁场下电阻率呈现的费米液体行为相吻合。As a recently discovered Ce-based 122-type heavy-fermion superconductor, CeRh2As2 has attracted significant attention due to its non-Fermi-liquid behavior and two-phase superconductivity. The tetragonal crystal structure of CeRh2As2 maintains global centrosymmetry which allows even-parity and odd-parity superconducting states to be distinct rather than mixed. The Ce site exhibits local inversion symmetry breaking which enables staggered Rashba spin-orbit coupling. This may lead to the c axis field-induced transition between two superconducting phases and high critical field. Given the novel physics in CeRh2As2, including a possible quantum critical point and a spin-fluctuation-mediated superconducting pairing mechanism, this work investigates the ultra-low-temperature electrical and thermal transport properties of CeRh2As2 under various magnetic fields. The zero-field resistivity reveals a superconducting transition at the critical temperature Tc = 0.34 K. Under 1 T magnetic field, a resistivity minimum emerges near T0≈0.42 K, likely arising from partial gap opening due to Fermi surface nesting, indicating the system enters into a magnetically ordered state, while this feature isn’t observed in zero field. In the temperature range from T0 to 2 K, the system exhibits non-Fermi-liquid behavior ρ~T0.44, suggesting proximity to a quantum critical point. The superconducting transition is fully suppressed at 7 T, with resistivity recovering Fermi-liquid behavior at low temperature. No significant anomaly is observed near Tc in the zero-field thermal conductivity of CeRh2As2. This absence of anomaly may be attributed to the high residual resistivity of the sample, and the reduction in carrier density during the superconducting transition and the T0 phase transition. It requirs optimizing single crystal growth to reduce the effects of lattice defects or chemical disorder on thermal transport. Upon applying magnetic field, the thermal conductivity curve exhibits a small upward shift relative to its zero-field curve. At 0.15 K, thermal conductivity rises with increasing magnetic field and saturates at higher fields above 5 T. In the normal state at 7 T, we find that the electrical resistivity and thermal conductivity satisfy the Wiedemann-Franz law, indicating that the charge and heat transport are governed by the same quasiparticles, consistent with the Fermi-liquid behavior observed in resistivity under this field.
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Keywords:
- Heavy-fermion superconductor /
- CeRh2As2 /
- Electrical resistivity /
- Ultra-low-temperature thermal conductivity
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