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[论文解读] Nematic-fluctuation-mediated superconductivity in CuxTiSe2

Xingyu Lv, Yang Fu|arXiv (Cornell University)|Jan 2, 2026
2D Materials and Applications被引用 0
一句话总结

本论文通过弹性电阻率研究Cu掺杂TiSe2中的向列涨落，显示Curie-Weiss型温度依赖，并将向列特征温度T*与CDW抑制及超导增强联系起来。

ABSTRACT

The interplay among electronic nematicity, charge density wave, and superconductivity in correlated electronic systems has induced extensive research interest. Here, we discover the existence of nematic fluctuations in TiSe2 single crystal and investigate its evolution with Cu intercalation. It is observed that the elastoresistivity coefficient mEg exhibits a divergent temperature dependence following a Curie-Weiss law at high temperature. Upon Cu intercalation, the characteristic temperature T* of nematic fluctuation is progressively suppressed and becomes near zero when the superconductivity is optimized. Further intercalation of Cu leads to the sign change of T* and the suppression of superconductivity. These results strongly indicate that nematic phase transition may play a vital role in enhancing superconductivity in CuxTiSe2. Therefore, CuxTiSe2 provides a unique material platform to explore the nematic-fluctuation-mediated superconductivity.

研究动机与目标

  • 研究TiSe2与Cu_xTiSe2中电子向列涨落的存在与演化。
  • 理解Cu插层如何影响向列性、CDW有序及超导性。
  • 确定向列涨落是否与Cu_xTiSe2中的超导岛形（dome）形成相关。

提出的方法

  • 对TiSe2与Cu_xTiSe2单晶进行改良的Montgomery方法的弹性电阻率测量。
  • 将弹性电阻率分解为A1g与Eg对称通道，以探测电子向列性。
  • 通过m_Eg提取向列敏感性，并拟合其高温行为为Curie-Weiss型：-m_Eg = λ/[a(T - T*)] + m_Eg^0。
  • 随着Cu含量x的变化，跟踪表征性向列温度T*的温度依赖。
  • 绘制相图，显示T*、TCDW和Tc随Cu含量x的关系。
  • 参考结构与CDW转变，并将其与向列涨落联系起来。
Figure 1: (a) XRD pattern of a Cu x TiSe 2 single crystal. Inset: crystal structure of Cu x TiSe 2 . The small blue, large red and medium orange balls represent Cu, Ti and Se atoms, respectively. (b) Temperature dependence of $\rho_{xx}(T)$ for different Cu content $x$ . Inset: enlarged view of $\rh
Figure 1: (a) XRD pattern of a Cu x TiSe 2 single crystal. Inset: crystal structure of Cu x TiSe 2 . The small blue, large red and medium orange balls represent Cu, Ti and Se atoms, respectively. (b) Temperature dependence of $\rho_{xx}(T)$ for different Cu content $x$ . Inset: enlarged view of $\rh

实验结果

研究问题

  • RQ1TiSe2是否通过Eg通道的弹性电阻率证据表现出向列涨落？
  • RQ2Cu插层如何改变向列涨落温度T*及其与CDW和超导性的关系？
  • RQ3向列相变（或涨落）是否与Cu_xTiSe2中Tc的增强相关？
  • RQ4Curie-Weiss型向列敏感性是否能描述这些材料中m_Eg的高温行为？

主要发现

  • TiSe2的弹性电阻率显示Eg通道系数-m_Eg在接近TCDW的温度下降时发散，指示向列涨落。
  • 高温下的m_Eg(T)符合Curie-Weiss形式，TiSe2的拟合魏斯温标T*约为181.6 K。
  • Cu插层将向列涨落峰移至更低温度并降低其幅值，T*在接近最优超导（x≈0.08）时趋近于0。
  • 超过最优掺杂（x ≳ 0.1）时向列涨落减弱，CDW进一步抑制，而超导在1.6 K以上消失。
  • 相图显示T*、TCDW和Tc随Cu含量x的关系，表明向列跃迁/涨落与Cu_xTiSe2中Tc的增强密切相关。
Figure 2: Relative changes in resistivity (a) ( $\Delta\rho/\rho)_{xx}$ and (b) ( $\Delta\rho/\rho)_{yy}$ of TiSe 2 single crystal at various temperatures above $T_{\rm CDW}$ as a function of strain $\epsilon_{xx}$ applied via an attached piezoelectric actuator. Inset of (b) shows a schematic experi
Figure 2: Relative changes in resistivity (a) ( $\Delta\rho/\rho)_{xx}$ and (b) ( $\Delta\rho/\rho)_{yy}$ of TiSe 2 single crystal at various temperatures above $T_{\rm CDW}$ as a function of strain $\epsilon_{xx}$ applied via an attached piezoelectric actuator. Inset of (b) shows a schematic experi

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