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Multiple correlation lengths and type-1.5 superconductivity in U(1) superconductors due to hidden competition between irreducible representations of nonlocal pairing

Anton Talkachov1,*, Paul Leask1, and Egor Babaev1,2

  • *Contact author: anton.talkachov@gmail.com
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Phys. Rev. B 113, 224520 – Published 18 June, 2026

DOI: https://doi.org/10.1103/bf2v-wtkt

Abstract

The ratio of magnetic field penetration length λ and superconducting coherence length ξ is a defining quantity that governs magnetic response and underpins the conventional type-I and type-II classification of superconductors. While multicomponent superconductors are known to exhibit multiple coherence lengths with rich and often exotic behavior, single-component superconductors are traditionally assumed to be fully characterized by a single Ginzburg-Landau parameter. Here we revisit this concept. We demonstrate that even nominally single-component superconductors are, in general, intrinsically characterized by multiple coherence lengths. Specifically, we analyze a common physical situation in which a subdominant pairing channel is fully suppressed in the ground state, yielding a nominally single-component superconducting ground state. We show that, nonetheless, proximity to a competing pairing instability generically gives rise to multiple correlation lengths with a nontrivial hierarchy. This has consequences for all inhomogeneous states. Especially near a competing pairing instability, the magnetic field penetration depth lies between two distinct coherence lengths, leading to a breakdown of the conventional type-I and type-II dichotomy and enabling the coexistence of vortex clusters and Meissner domains. More broadly, we find that superconducting states cannot, in general, be classified by a single fundamental length scale, even in ostensibly conventional single-component systems.

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Outline

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Phys. Rev. B 113, 224520– Published 18 June, 2026
  • Received 23 November 2025
  • Revised 19 March 2026
  • Accepted 11 May 2026
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