2 research outputs found
Two-gap to single-gap superconducting transition on a honeycomb lattice in Ca1−xSrxAlSi
We report on the structural and microscopic superconducting properties of the Ca1−xSrxAlSi solid solution. Specifically, we have realized the continuous solid solution, which for all members, other than x=0 (CaAlSi), crystallizes in the AlB2-type structure. For CaAlSi, we present an improved structural model where all Al/Si layers are buckled, leading to a 6-folded structure along the crystallographic c direction. We, furthermore, find indications for the structural instability in the parent compound CaAlSi to enhance the superconductivity across the solid solution. Our investigation of the magnetic penetration depths by means of muon-spin rotation experiments reveals that CaAlSi is a two-gap superconductor, that SrAlSi is a single-gap superconductor, and that there is a continuous transition from one electronic state to the other across the solid solution. Hence, we show that the Ca1−xSrxAlSi solid solution is a highly tunable two-gap to single-gap superconducting system on a honeycomb lattice, where the superconductivity is strongly connected to a structural instability, i.e., the buckling of the Al/Si layers
Structural Phase Transition and Superconductivity in 2H-BaGaGe with Buckled Honeycomb Layers
We report on the structural and superconducting properties of the
intermetallic compound BaGaGe. We find that this material undergoes a
structural second-order phase transition from the distorted AlB-type
structure (1H, = 4.3254(2) \r{A}, = 5.1078(3) \r{A}, P6/mmm) into the
CaIn-type structure (2H, = 4.3087(3) \r{A}, = 10.2117(6) \r{A},
P6/mmc) at a transition temperature of = 253 K. We find that
the structural phase-transition corresponds to a coherent buckling of the
honeycomb layers, which we can interpret as a disorder-to-order transition of
the atoms located within this layer. We show that the 2H-BaGaGe phase becomes
superconducting at a critical temperature of = 2.1 K. The bulk
nature of the superconductivity in 2H-BaGaGe is confirmed by means of specific
heat measurements, where we determine a value of /
= 1.59, which is close to the expected BCS value in the weak coupling limit