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[Paper Review] Nematic-fluctuation-mediated superconductivity in CuxTiSe2

Xingyu Lv, Yang Fu|arXiv (Cornell University)|Jan 2, 2026
2D Materials and Applications0 citations
TL;DR

The paper demonstrates nematic fluctuations in Cu-intercalated TiSe2 via elastoresistivity, shows a Curie-Weiss temperature dependence, and links the nematic characteristic temperature T* to CDW suppression and the enhancement of superconductivity.

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.

Motivation & Objective

  • Investigate the presence and evolution of electronic nematic fluctuations in TiSe2 and Cu_xTiSe2.
  • Understand how Cu intercalation affects nematicity, CDW order, and superconductivity.
  • Determine whether nematic fluctuations correlate with superconducting dome formation in Cu_xTiSe2.

Proposed method

  • Perform elastoresistivity measurements on TiSe2 and Cu_xTiSe2 single crystals using a modified Montgomery technique.
  • Decompose elastoresistivity into A1g and Eg symmetry channels to probe electronic nematicity.
  • Extract nematic susceptibility from elastoresistivity via m_Eg and fit its high-temperature behavior to a Curie-Weiss form: -m_Eg = λ/[a(T - T*)] + m_Eg^0.
  • Track the temperature dependence of the characteristic nematic temperature T* as Cu content x is varied.
  • Construct a phase diagram showing T*, TCDW, and Tc versus Cu content x.
  • Reference structural and CDW transitions and relate them to nematic fluctuations.
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

Experimental results

Research questions

  • RQ1Does TiSe2 exhibit nematic fluctuations as evidenced by elastoresistivity in the Eg channel?
  • RQ2How does Cu intercalation modify the nematic fluctuation temperature T* and its relation to CDW and superconductivity?
  • RQ3Is there a correlation between the nematic phase transition (or fluctuations) and the enhancement of Tc in Cu_xTiSe2?
  • RQ4Can Curie-Weiss-like nematic susceptibility describe the high-temperature behavior of m_Eg in these materials?

Key findings

  • Elastoresistivity in TiSe2 shows a divergent Eg channel coefficient -m_Eg with decreasing temperature near TCDW, indicating nematic fluctuations.
  • The high-temperature m_Eg(T) follows a Curie-Weiss form, with a fitted Weiss temperature T* ≈ 181.6 K for TiSe2.
  • Cu intercalation shifts the nematic fluctuation peak to lower temperatures and reduces its magnitude, with T* approaching zero near optimal superconductivity (x ≈ 0.08).
  • Beyond optimal doping (x ≳ 0.1), nematic fluctuations weaken and CDW is further suppressed, while superconductivity vanishes above 1.6 K.
  • A phase diagram shows T*, TCDW, and Tc versus Cu content x, illustrating that nematic transitions/fluctuations are intimately linked to Tc enhancement in Cu_xTiSe2.
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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This review was created by AI and reviewed by human editors.