Nodeless Versus Nodal Scenarios of Possible Triplet Superconductivity in the Quasi-One-Dimensional Layered Conductor Li\(_{0.9}\)Mo\(_6\)O\(_{17}\)

Abstract

We consider the problem of the orbital upper critical magnetic field, parallel to the most conducting axis of a quasi-one-dimensional layered superconductor. It is shown that superconductivity can be destroyed through orbital effects at fields much higher than the so-called Clogston-Chandrasekhar paramagnetic limiting field, \(H_p\), provided that superconducting pairing of electrons are of a triplet nature. We demonstrate that the superconducting state of the quasi-one-dimensional layered conductor, \(\mathrm{Li_{0.9}Mo_6O_{17}}\), is well described by the suggested theory. To this end, we consider two competing scenarios: 1: a superconducting order parameter without zeros on the Fermi surface, and 2: one with zeros on the Fermi surface - both are shown to lead to destruction of superconductivity at a magnetic field, \(H^x_{c_2}\), five times higher than \(H_p\). With recent experimental measurements on the \(\mathrm{Li_{0.9}Mo_6O_{17}}\) favoring the nodeless order parameter, we present a strong argument supporting triplet pairing in this compound.