Fig. 4: Hybridized g-factor spectroscopy.
From: A quantum dot in germanium proximitized by a superconductor
a–c, Bias spectroscopy displayed in logarithmic scale at magnetic field strengths of 50 mT, 250 mT and 350 mT, respectively, with the barrier gates set to VRB = −1.4100 V, VLB = −0.8070 V and VHG = −0.9575 V. Sub-gap energy splitting is visible in b and c. The superimposed orange markers in a–c serve as a qualitative comparison between the measured transport data and calculations using a ZBW model, inputting Δ = 71 μeV, hybridization energy ΓS = 110 μeV and charging energy U = 1.6 meV, as well as a Zeeman energy (EZ) of \({E}_{\mathrm{Z}}^{{\mathrm{SC}}}=4\,\upmu {\mathrm{eV}}\) on the SC and \({E}_{{\mathrm{Z}}}^{{\mathrm{QD}}}=4\,\upmu {\rm{eV}}\) on the QD; \({E}_{{\mathrm{Z}}}^{{\mathrm{SC}}}=44\,\upmu {\rm{eV}}\) on the SC and \({E}_{{\mathrm{Z}}}^{{\mathrm{QD}}}=44\,\upmu {\rm{eV}}\) on the QD; and \({E}_{{\mathrm{Z}}}^{{\mathrm{SC}}}=56\,\upmu {\rm{eV}}\) on the SC and \({E}_{{\mathrm{Z}}}^{{\mathrm{QD}}}=56\,\upmu {\rm{eV}}\) on the QD, respectively for a through c. d, Magnetic field sweep at VRB = −1.4100 V, VLB = −0.8070 V, VHG = −0.9575 V and VPG = −1.8027 V tuned within the singlet ground state, as indicated by the red notch in a. We extract a g-factor for the out-of-plane magnetic field splitting g⊥ = 1.5 ± 0.2. e–g, Bias spectroscopy of rotating magnetic field at total magnetic field strength ∣B∣ = 420 mT and VPG = −1.8028 V, also tuned to the singlet ground state. Strong g-tensor anisotropy is observed between out-of-plane and in-plane magnetic field orientations (Bx and By), as defined by the coordinate system in Fig. 1a.
