Pair density wave at high magnetic fields in cuprates with charge and spin orders

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Underdoped cuprates exhibit complex interplay between pseudogap, superconductivity, and charge/spin ordering.
• Exotic quantum states, such as the pair density wave (PDW), are proposed but lack conclusive evidence.
• The PDW state, characterized by an oscillatory superconducting order parameter, is crucial for understanding cuprate physics.

Purpose of the Study:

• To investigate the existence and properties of the pair density wave (PDW) state in specific underdoped cuprates.
• To test the role of interlayer frustration, a key component of the PDW theoretical model.
• To identify transport signatures of the PDW in the presence of quantum phase fluctuations that suppress superconductivity.

Main Methods:

• Transport measurements were conducted on charge- and spin-stripe-ordered La$_{1.7}$Eu$_{0.2}$Sr$_{0.1}$CuO$_{4}$ and La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$.
• Experiments utilized perpendicular magnetic fields (H⊥) and an additional in-plane field (H∥) applied parallel to CuO$_{2}$ layers.
• Analysis focused on detecting phenomena predicted by the PDW model, particularly changes in interlayer superconducting phase coherence.

Main Results:

• Observed phenomena consistent with the predictions of the pair density wave (PDW) state.
• Detected an enhancement of interlayer superconducting phase coherence as the parallel magnetic field (H∥) increased.
• Provided crucial transport signatures of the PDW in a regime where superconductivity is typically destroyed by quantum fluctuations.

Conclusions:

• The study provides compelling evidence for the existence of the pair density wave (PDW) state in the investigated cuprates.
• The results validate the importance of interlayer frustration in the PDW picture and its influence on superconductivity.
• These findings offer new insights into the complex electronic phase diagram of cuprates and the nature of exotic quantum states.