Roton pair density wave in a strong-coupling kagome superconductor

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Superconductivity

Background:

• Transition metal kagome lattices exhibit complex quantum phenomena.
• Vanadium-based kagome metals (AV3Sb5) display topological band structures.
• These materials undergo charge density wave transitions and exhibit superconductivity.

Purpose of the Study:

• To investigate unconventional superconductivity in CsV3Sb5.
• To identify and characterize novel quantum states, specifically a pair density wave (PDW).
• To explore the relationship between PDW, charge order, and superconductivity.

Main Methods:

• Scanning tunnelling microscopy/spectroscopy (STM/STS).
• Josephson scanning tunnelling spectroscopy.
• Probing electronic states under applied magnetic fields and varying temperatures.

Main Results:

• Observation of unconventional superconductivity with a V-shaped pairing gap (Δ ~ 0.5 meV) in CsV3Sb5.
• Coexistence of superconductivity with charge order (4a0 unidirectional and 2a0 × 2a0).
• Discovery of a 3Q pair density wave (PDW) with unique spatial modulations, termed a 'roton PDW'.
• Identification of the PDW as a primary state responsible for emergent pseudogap and intertwined electronic order.

Conclusions:

• CsV3Sb5 hosts a novel quantum state, the roton PDW, intertwined with superconductivity.
• The PDW state is fundamental to the observed electronic order and pseudogap phenomena.
• Findings offer insights into correlated electronic states and superconductivity in kagome metals, with parallels to high-Tc cuprates.