Two-gap superconductivity in Cu$_{\mathrm{0.09}}$TiSe$_{\mathrm{2}}$ via penetration depth measurements

TiSe$_{\mathrm{2}}$ is an example of a transition-metal dichalcogenide, in which Cu intercalation systematically suppresses the charge-density-wave transition temperature and gives rise to superconductivity. We report magnetic penetration depth measurements of Cu$_{\mathrm{0.09}}$TiSe$_{\mathrm{2}}$ (from 350 mK to T$_{\mathrm{C}}=$ 3 K), using a self-made high sensitivity tunnel-diode-based oscillator setup. Our analysis of the normalized superfluid density data points to a two-gap isotropic s-wave scenario, with the smaller gap $\Delta _{\mathrm{1}}$(0) $=$ 1.2k$_{\mathrm{B}}$T$_{\mathrm{C}}$, and the larger gap $\Delta_{\mathrm{2}}$(0) $=$ 2.0k$_{\mathrm{B}}$T$_{\mathrm{C}}$. Our proposed two-gap scenario is supported by ARPES (that clearly shows two Fermi sheets for Cu$_{\mathrm{x}}$TiSe$_{\mathrm{2}})$ and muon spin rotation data.