@unpublished{13312,
  abstract     = {Superconductor/semiconductor hybrid devices have attracted increasing
interest in the past years. Superconducting electronics aims to complement
semiconductor technology, while hybrid architectures are at the forefront of
new ideas such as topological superconductivity and protected qubits. In this
work, we engineer the induced superconductivity in two-dimensional germanium
hole gas by varying the distance between the quantum well and the aluminum. We
demonstrate a hard superconducting gap and realize an electrically and flux
tunable superconducting diode using a superconducting quantum interference
device (SQUID). This allows to tune the current phase relation (CPR), to a
regime where single Cooper pair tunneling is suppressed, creating a $ \sin
\left( 2 \varphi \right)$ CPR. Shapiro experiments complement this
interpretation and the microwave drive allows to create a diode with $ \approx
100 \%$ efficiency. The reported results open up the path towards monolithic
integration of spin qubit devices, microwave resonators and (protected)
superconducting qubits on a silicon technology compatible platform.},
  author       = {Valentini, Marco and Sagi, Oliver and Baghumyan, Levon and Gijsel, Thijs de and Jung, Jason and Calcaterra, Stefano and Ballabio, Andrea and Servin, Juan Aguilera and Aggarwal, Kushagra and Janik, Marian and Adletzberger, Thomas and Souto, Rubén Seoane and Leijnse, Martin and Danon, Jeroen and Schrade, Constantin and Bakkers, Erik and Chrastina, Daniel and Isella, Giovanni and Katsaros, Georgios},
  booktitle    = {arXiv},
  keywords     = {Mesoscale and Nanoscale Physics},
  title        = {{Radio frequency driven superconducting diode and parity conserving  Cooper pair transport in a two-dimensional germanium hole gas}},
  doi          = {10.48550/arXiv.2306.07109},
  year         = {2023},
}

@article{10025,
  abstract     = {Ferromagnetism is most common in transition metal compounds but may also arise in low-density two-dimensional electron systems, with signatures observed in silicon, III-V semiconductor systems, and graphene moiré heterostructures. Here we show that gate-tuned van Hove singularities in rhombohedral trilayer graphene drive the spontaneous ferromagnetic polarization of the electron system into one or more spin- and valley flavors. Using capacitance measurements on graphite-gated van der Waals heterostructures, we find a cascade of density- and electronic displacement field tuned phase transitions marked by negative electronic compressibility. The transitions define the boundaries between phases where quantum oscillations have either four-fold, two-fold, or one-fold degeneracy, associated with a spin and valley degenerate normal metal, spin-polarized `half-metal', and spin and valley polarized `quarter metal', respectively. For electron doping, the salient features are well captured by a phenomenological Stoner model with a valley-anisotropic Hund's coupling, likely arising from interactions at the lattice scale. For hole filling, we observe a richer phase diagram featuring a delicate interplay of broken symmetries and transitions in the Fermi surface topology. Finally, by rotational alignment of a hexagonal boron nitride substrate to induce a moiré superlattice, we find that the superlattice perturbs the preexisting isospin order only weakly, leaving the basic phase diagram intact while catalyzing the formation of topologically nontrivial gapped states whenever itinerant half- or quarter metal states occur at half- or quarter superlattice band filling. Our results show that rhombohedral trilayer graphene is an ideal platform for well-controlled tests of many-body theory and reveal magnetism in moiré materials to be fundamentally itinerant in nature.},
  author       = {Zhou, Haoxin and Xie, Tian and Ghazaryan, Areg and Holder, Tobias and Ehrets, James R. and Spanton, Eric M. and Taniguchi, Takashi and Watanabe, Kenji and Berg, Erez and Serbyn, Maksym and Young, Andrea F.},
  issn         = {1476-4687},
  journal      = {Nature},
  keywords     = {condensed matter - mesoscale and nanoscale physics, condensed matter - strongly correlated electrons, multidisciplinary},
  publisher    = {Springer Nature},
  title        = {{Half and quarter metals in rhombohedral trilayer graphene}},
  doi          = {10.1038/s41586-021-03938-w},
  year         = {2021},
}

@article{9928,
  abstract     = {There are two elementary superconducting qubit types that derive directly from the quantum harmonic oscillator. In one, the inductor is replaced by a nonlinear Josephson junction to realize the widely used charge qubits with a compact phase variable and a discrete charge wave function. In the other, the junction is added in parallel, which gives rise to an extended phase variable, continuous wave functions, and a rich energy-level structure due to the loop topology. While the corresponding rf superconducting quantum interference device Hamiltonian was introduced as a quadratic quasi-one-dimensional potential approximation to describe the fluxonium qubit implemented with long Josephson-junction arrays, in this work we implement it directly using a linear superinductor formed by a single uninterrupted aluminum wire. We present a large variety of qubits, all stemming from the same circuit but with drastically different characteristic energy scales. This includes flux and fluxonium qubits but also the recently introduced quasicharge qubit with strongly enhanced zero-point phase fluctuations and a heavily suppressed flux dispersion. The use of a geometric inductor results in high reproducibility of the inductive energy as guaranteed by top-down lithography—a key ingredient for intrinsically protected superconducting qubits.},
  author       = {Peruzzo, Matilda and Hassani, Farid and Szep, Gregory and Trioni, Andrea and Redchenko, Elena and Zemlicka, Martin and Fink, Johannes M},
  issn         = {2691-3399},
  journal      = {PRX Quantum},
  keywords     = {quantum physics, mesoscale and nanoscale physics},
  number       = {4},
  pages        = {040341},
  publisher    = {American Physical Society},
  title        = {{Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction}},
  doi          = {10.1103/PRXQuantum.2.040341},
  volume       = {2},
  year         = {2021},
}