Two-dimensional nature of superconductivity in the intercalated layered systems LixHfNCl and LixZrNCl: Muon spin relaxation and magnetization measurements

Ito T.

Fukaya A.

Gat-Malureanu I. M.

Larkin M. I.

Russo P. L.

Savici A.

Uemura Y. J.

Groves K.

Breslow R.

Hotehama K.

Yamanaka Shoji

Kyriakou P.

Rovers M.

Luke G. M.

Kojima K. M.

Physical Review B - Condensed Matter and Materials Physics

We report muon spin relaxation (μSR) and magnetization measurements, together with synthesis and characterization, of the Li-intercalated layered superconductors LixHfNCl and LixZrNCl with/without cointercalation of THF (tetrahydrofuran) or propylene carbonate. The three-dimensional superfluid density ns/m* (superconducting carrier density/effective mass) as well as the two-dimensional superfluid density ns2D/m*ab [two-dimensional (2D) area density of superconducting carriers/ab-plane effective mass] have been derived from the μSR results of the magnetic-field penetration depth λ ab observed with external magnetic field applied perpendicular to the 2D honeycomb layer of HfN/ZrN. In a plot of Tc versus n s2D/m*ab, most of the results lie close to the linear relationship found for underdoped high-Tc cuprate (HTSC) and layered organic BEDT (bis(ethylenedithio)) superconductors. In Li xZrNCl without THF intercalation, the superfluid density and T c for x = 0.17 and 0.4 do not show much difference, reminiscent of μSR results for some overdoped HTSC systems. Together with the absence of dependence of Tc on average interlayer distance among ZrN/HfN layers, these results suggest that the 2D superfluid density ns2D/m* ab is a dominant determining factor for Tc in the intercalated nitride-chloride systems. We also report μSR and magnetization results on depinning of flux vortices, and the magnetization results for the upper critical field Hc2 and the penetration depth λ. A reasonable agreement was obtained between μSR and magnetization estimates of λ. We discuss the two-dimensional nature of superconductivity in the nitride-chloride systems based on these results.

Physics [ 420 ]

eng

American Physical Society

[NCID] AA11187113

[ISSN] 1098-0121

[DOI] 10.1103/PhysRevB.69.134522

[DOI] http://dx.doi.org/10.1103/PhysRevB.69.134522