Low Frequency Nonlinear Magnetic Response of an Unconventional Superconductor

Abstract

We consider an unconventional superconductor in a low frequency harmonic magnetic field. In the Meissner regime at low T a nonlinear magnetic response arises from quasiparticle excitations near minima in the energy gap. Various physical quantities then acquire higher harmonics of the frequency of the applied field. We discuss how examination of the field and angular dependence of these harmonics allows determination of the structure of the energy gap. We show how to distinguish nodes from small finite minima ("quasinodes"). Gaps with nodal lines give rise to universal power law field dependences for the nonlinear magnetic moment and the nonlinear torque. They both have separable temporal and angular dependences. In contrast, when there are quasinodes these quantities have more complicated and nonseparable field, temporal, and angular dependences. We illustrate this on the example of an s+id gap. We discuss how to perform measurements so as to maximize the nonlinear signal and how to investigate in detail the properties of the superconducting minima, thus determining the gap function symmetry.

To appear in Phys Rev B. Ten figures, 13 text pages

References in corpus (4)

• The Order Parameter for the Superconducting Phases of UPt${}_3$
• Low Temperature Behavior of the Vortex Lattice in Unconventional Superconductors
• On the T-dependence of the magnetic penetration depth in unconventional superconductors at low temperatures: can it be linear?
• Computation of the Nonlinear Magnetic Response of a Three Dimensional Anisotropic Superconductor

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• Free Energy and Magnetic Penetration Depth of a $d$-Wave Superconductor in the Meissner State
• Probing Majorana-like states in quantum dots and quantum rings
• Comment on "Is the nonlinear Meissner effect unobservable?"
• Magnetic field effects on the density of states of orthorhombic superconductors
• Nonlinear electrodynamics of p-wave superconductors
• Angular dependence of the penetration depth in unconventional superconductors