Superconducting ground state of quasi-one-dimensional K2Cr3As3 investigated using μSR measurements

Abstract

The superconducting state of the newly discovered superconductor K2Cr3As3, with a quasi-one-dimensional crystal structure (Tc∼6K), is investigated using magnetization and muon-spin relaxation or rotation (μSR) measurements. Our analysis shows that the temperature dependence of the superfluid density obtained from transverse-field μSR measurements fits either to an isotropic s-wave character for the superconducting gap or to a d-wave model with line nodes. Furthermore, the goodness-of-fit (χ2) values indicate that our data fit better to the d-wave model (χ2∼1) than the s-wave model (χ2∼1.38). Therefore our μSR analysis is more consistent with having line nodes than being fully gapped, which is in agreement with the results of the penetration depth measured using a tunnel diode oscillator technique. Our zero-field μSR measurements do reveal very weak evidence of the spontaneous appearance of an internal magnetic field below the transition temperature, which might indicate that the superconducting state is not conventional. This observation suggests that the electrons are paired via unconventional channels such as spin fluctuations, as proposed on the basis of theoretical models of K2Cr3As3. Furthermore, from our transverse-field μSR study the magnetic penetration depth λL, superconducting carrier density ns, and effective-mass enhancement m* have been estimated to be λL(0)=432(4) nm, ns=2.7×1027carriers/m3, and m*=1.75me, respectively.

Source-reported materials — not catalogue approval

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