Directly visualizing nematic superconductivity driven by the pair density wave in NbSe${}_2$

Abstract

Pair density wave (PDW) is a distinct superconducting state characterized by a periodic modulation of its order parameter in real space. Its intricate interplay with the charge density wave (CDW) state is a continuing topic of interest in condensed matter physics. While PDW states have been discovered in cuprates and other unconventional superconductors, the understanding of diverse PDWs and their interactions with different types of CDWs remains limited. Here, utilizing scanning tunneling microscopy, we unveil the subtle correlations between PDW ground states and two distinct CDW phases -- namely, anion-centered-CDW (AC-CDW) and hollow-centered-CDW (HC-CDW) -- in 2H-NbSe${}_2$. In both CDW regions, we observe coexisting PDWs with a commensurate structure that aligns with the underlying CDW phase. The superconducting gap size, $\Delta (r)$, related to the pairing order parameter is in phase with the charge density in both CDW regions. Meanwhile, the coherence peak height, $H(r)$, qualitatively reflecting the electron-pair density, exhibits a phase difference of approximately $2\pi /3$ relative to the CDW. The three-fold rotational symmetry is preserved in the HC-CDW region but is spontaneously broken in the AC-CDW region due to the PDW state, leading to the emergence of nematic superconductivity.

21 pages, 5 figures

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Cited by in corpus (10)

• Twisted Bogoliubov quasiparticles in the superconducting NbSe${}_2$ monolayer on graphene
• Vestigial $d$-wave charge-$4e$ Superconductivity from Bidirectional Pair Density Waves
• Switchable chiral 2x2 pair density wave in pure CsV3Sb5
• Phase-sensitive evidence for pair density waves in a kagome superconductor
• Modulation of superconducting properties by the charge density wave at the surface of 2H-NbSe2
• Pressure induced magnetic-field-free superconducting diode effect in NbSe2 flake
• Visualizing Pair-breaking Scattering Interference in Bulk FeSe
• Supercurrent effect in a charge density wave intertwined superconductor
• Probing Quantum Geometric Phases via Scanning Tunneling Microscopy
• Evidence of intertwined pair density and charge density wave orders in UTe2