Magnetic field induced criticality in superconducting two-leg ladders

TL;DR

This paper investigates how magnetic fields induce quantum critical behavior in the superconducting phase of doped two-leg ladders, revealing distinct singularities compared to undoped Mott insulators.

Contribution

It demonstrates that magnetic fields cause logarithmic singularities in thermodynamic quantities in doped ladders, contrasting with the square root singularities in undoped systems.

Findings

Logarithmic singularities in specific heat and susceptibility in doped ladders.

Different critical behavior between doped and undoped ladder systems.

Magnetic field effects depend on the quantum numbers of low-energy excitations.

Abstract

We study critical singularities in the d-wave-like superconducting phase of the hole-doped Hubbard model of repulsively interacting electrons, defined on a two-leg ladder, induced by a magnetic field applied parallel to the ladder plane. We argue that, provided the lowest energy spin excitations in doped ladders carry as well charge quantum numbers, the low temperature thermodynamic quantities, such as specific heat coefficient and magnetic susceptibility will show logarithmic singularities in quantum critical regime. This behavior is in drastic contrast with the magnetic field induced criticality in undoped Mott insulator ladders, which is governed by the zero scle-factor universality with its hallmark square root singularities.