Coherent Superconductivity with a Large Gap Ratio from Incoherent Metals

Area of Science:

• Condensed Matter Physics
• Quantum Materials

Background:

• The incoherent metallic (IM) normal state, characterized by T-linear resistivity, is a common feature in strongly correlated superconductors.
• Understanding the transition from this mysterious IM state to superconductivity is crucial for advancing the field.

Purpose of the Study:

• To investigate new microscopic models exhibiting direct transitions into a superconducting state from an IM state.
• To explore the properties of superconductivity emerging from an IM normal state using connected Sachdev-Ye-Kitaev (SYK) quantum dots.

Main Methods:

• Utilizing a theoretical framework based on connected Sachdev-Ye-Kitaev quantum dots.
• Performing explicit calculations to analyze the transport properties and superconducting characteristics.

Main Results:

• Demonstrated that despite the absence of quasiparticles in the IM normal state, coherent superfluid transport emerges in the superconducting state.
• Observed a significant enhancement in the ratio of the superconducting gap to the transition temperature (2Δ/T_{SC}), exceeding the Bardeen-Cooper-Schrieffer (BCS) value.

Conclusions:

• The study provides a microscopic model for superconductivity directly from an IM state.
• The findings highlight unique features of superconductivity in strongly correlated systems, including enhanced gap ratios and coherent transport from a non-quasiparticle normal state.