---
_id: '13312'
abstract:
- lang: eng
  text: "Superconductor/semiconductor hybrid devices have attracted increasing\r\ninterest
    in the past years. Superconducting electronics aims to complement\r\nsemiconductor
    technology, while hybrid architectures are at the forefront of\r\nnew ideas such
    as topological superconductivity and protected qubits. In this\r\nwork, we engineer
    the induced superconductivity in two-dimensional germanium\r\nhole gas by varying
    the distance between the quantum well and the aluminum. We\r\ndemonstrate a hard
    superconducting gap and realize an electrically and flux\r\ntunable superconducting
    diode using a superconducting quantum interference\r\ndevice (SQUID). This allows
    to tune the current phase relation (CPR), to a\r\nregime where single Cooper pair
    tunneling is suppressed, creating a $ \\sin\r\n\\left( 2 \\varphi \\right)$ CPR.
    Shapiro experiments complement this\r\ninterpretation and the microwave drive
    allows to create a diode with $ \\approx\r\n100 \\%$ efficiency. The reported
    results open up the path towards monolithic\r\nintegration of spin qubit devices,
    microwave resonators and (protected)\r\nsuperconducting qubits on a silicon technology
    compatible platform."
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
acknowledgement: "The authors acknowledge Alexander Brinkmann, Alessandro Crippa,
  Andrew Higginbotham, Andrea Iorio, Giordano\r\nScappucci and Christian Schonenberger
  for helpful discussions. We thank Marcel Verheijen for the support in the\r\nTEM
  analysis. This research and related results were made\r\npossible with the support
  of the NOMIS Foundation. It was\r\nsupported by the Scientific Service Units of
  ISTA through resources provided by the MIBA Machine Shop and the\r\nnanofabrication
  facility, the European Union’s Horizon 2020\r\nresearch and innovation programme
  under Grant Agreement\r\nNo 862046, the HORIZON-RIA 101069515 project and the\r\nFWF
  Projects #P-32235, #P-36507 and #F-8606. R.S.S.\r\nacknowledges Spanish CM “Talento
  Program” Project No.\r\n2022-T1/IND-24070."
article_number: '2306.07109'
article_processing_charge: No
arxiv: 1
author:
- first_name: Marco
  full_name: Valentini, Marco
  id: C0BB2FAC-D767-11E9-B658-BC13E6697425
  last_name: Valentini
- first_name: Oliver
  full_name: Sagi, Oliver
  id: 71616374-A8E9-11E9-A7CA-09ECE5697425
  last_name: Sagi
- first_name: Levon
  full_name: Baghumyan, Levon
  last_name: Baghumyan
- first_name: Thijs de
  full_name: Gijsel, Thijs de
  last_name: Gijsel
- first_name: Jason
  full_name: Jung, Jason
  id: 4C9ACE7A-F248-11E8-B48F-1D18A9856A87
  last_name: Jung
- first_name: Stefano
  full_name: Calcaterra, Stefano
  last_name: Calcaterra
- first_name: Andrea
  full_name: Ballabio, Andrea
  last_name: Ballabio
- first_name: Juan Aguilera
  full_name: Servin, Juan Aguilera
  last_name: Servin
- first_name: Kushagra
  full_name: Aggarwal, Kushagra
  id: b22ab905-3539-11eb-84c3-fc159dcd79cb
  last_name: Aggarwal
  orcid: 0000-0001-9985-9293
- first_name: Marian
  full_name: Janik, Marian
  id: 396A1950-F248-11E8-B48F-1D18A9856A87
  last_name: Janik
- first_name: Thomas
  full_name: Adletzberger, Thomas
  id: 38756BB2-F248-11E8-B48F-1D18A9856A87
  last_name: Adletzberger
- first_name: Rubén Seoane
  full_name: Souto, Rubén Seoane
  last_name: Souto
- first_name: Martin
  full_name: Leijnse, Martin
  last_name: Leijnse
- first_name: Jeroen
  full_name: Danon, Jeroen
  last_name: Danon
- first_name: Constantin
  full_name: Schrade, Constantin
  last_name: Schrade
- first_name: Erik
  full_name: Bakkers, Erik
  last_name: Bakkers
- first_name: Daniel
  full_name: Chrastina, Daniel
  last_name: Chrastina
- first_name: Giovanni
  full_name: Isella, Giovanni
  last_name: Isella
- first_name: Georgios
  full_name: Katsaros, Georgios
  id: 38DB5788-F248-11E8-B48F-1D18A9856A87
  last_name: Katsaros
  orcid: 0000-0001-8342-202X
citation:
  ama: Valentini M, Sagi O, Baghumyan L, et al. Radio frequency driven superconducting
    diode and parity conserving  Cooper pair transport in a two-dimensional germanium
    hole gas. <i>arXiv</i>. doi:<a href="https://doi.org/10.48550/arXiv.2306.07109">10.48550/arXiv.2306.07109</a>
  apa: Valentini, M., Sagi, O., Baghumyan, L., Gijsel, T. de, Jung, J., Calcaterra,
    S., … Katsaros, G. (n.d.). Radio frequency driven superconducting diode and parity
    conserving  Cooper pair transport in a two-dimensional germanium hole gas. <i>arXiv</i>.
    <a href="https://doi.org/10.48550/arXiv.2306.07109">https://doi.org/10.48550/arXiv.2306.07109</a>
  chicago: Valentini, Marco, Oliver Sagi, Levon Baghumyan, Thijs de Gijsel, Jason
    Jung, Stefano Calcaterra, Andrea Ballabio, et al. “Radio Frequency Driven Superconducting
    Diode and Parity Conserving  Cooper Pair Transport in a Two-Dimensional Germanium
    Hole Gas.” <i>ArXiv</i>, n.d. <a href="https://doi.org/10.48550/arXiv.2306.07109">https://doi.org/10.48550/arXiv.2306.07109</a>.
  ieee: M. Valentini <i>et al.</i>, “Radio frequency driven superconducting diode
    and parity conserving  Cooper pair transport in a two-dimensional germanium hole
    gas,” <i>arXiv</i>. .
  ista: Valentini M, Sagi O, Baghumyan L, Gijsel T de, Jung J, Calcaterra S, Ballabio
    A, Servin JA, Aggarwal K, Janik M, Adletzberger T, Souto RS, Leijnse M, Danon
    J, Schrade C, Bakkers E, Chrastina D, Isella G, Katsaros G. Radio frequency driven
    superconducting diode and parity conserving  Cooper pair transport in a two-dimensional
    germanium hole gas. arXiv, 2306.07109.
  mla: Valentini, Marco, et al. “Radio Frequency Driven Superconducting Diode and
    Parity Conserving  Cooper Pair Transport in a Two-Dimensional Germanium Hole Gas.”
    <i>ArXiv</i>, 2306.07109, doi:<a href="https://doi.org/10.48550/arXiv.2306.07109">10.48550/arXiv.2306.07109</a>.
  short: M. Valentini, O. Sagi, L. Baghumyan, T. de Gijsel, J. Jung, S. Calcaterra,
    A. Ballabio, J.A. Servin, K. Aggarwal, M. Janik, T. Adletzberger, R.S. Souto,
    M. Leijnse, J. Danon, C. Schrade, E. Bakkers, D. Chrastina, G. Isella, G. Katsaros,
    ArXiv (n.d.).
date_created: 2023-07-26T11:17:20Z
date_published: 2023-06-13T00:00:00Z
date_updated: 2024-02-07T07:52:32Z
day: '13'
ddc:
- '530'
department:
- _id: GeKa
- _id: M-Shop
doi: 10.48550/arXiv.2306.07109
ec_funded: 1
external_id:
  arxiv:
  - '2306.07109'
keyword:
- Mesoscale and Nanoscale Physics
language:
- iso: eng
license: https://creativecommons.org/licenses/by/4.0/
main_file_link:
- open_access: '1'
  url: https://doi.org/10.48550/arXiv.2306.07109
month: '06'
oa: 1
oa_version: Preprint
project:
- _id: 237E5020-32DE-11EA-91FC-C7463DDC885E
  call_identifier: H2020
  grant_number: '862046'
  name: TOPOLOGICALLY PROTECTED AND SCALABLE QUANTUM BITS
- _id: 237B3DA4-32DE-11EA-91FC-C7463DDC885E
  call_identifier: FWF
  grant_number: P32235
  name: Towards scalable hut wire quantum devices
- _id: bd8bd29e-d553-11ed-ba76-f0070d4b237a
  grant_number: P36507
  name: Merging spin and superconducting qubits in planar Ge
- _id: 34a66131-11ca-11ed-8bc3-a31681c6b03e
  grant_number: F8606
  name: Conventional and unconventional topological superconductors
- _id: bd5b4ec5-d553-11ed-ba76-a6eedb083344
  name: Protected states of quantum matter
publication: arXiv
publication_status: submitted
related_material:
  record:
  - id: '13286'
    relation: dissertation_contains
    status: public
status: public
title: Radio frequency driven superconducting diode and parity conserving  Cooper
  pair transport in a two-dimensional germanium hole gas
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: preprint
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2023'
...
---
_id: '10025'
abstract:
- lang: eng
  text: 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.
acknowledgement: "The authors acknowledge discussions with A. Macdonald, L. Fu, F.
  Wang and M. Zaletel. AFY acknowledges support of the National Science Foundation
  under DMR1654186, and the Gordon and Betty Moore Foundation under award GBMF9471.
  The authors acknowledge the use of the research facilities within the California
  NanoSystems Institute, supported by the University of California, Santa Barbara
  and the University of California, Office of the President.\r\nK.W. and T.T. acknowledge
  support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant
  Number JPMXP0112101001 and JSPS KAKENHI, Grant Number JP20H00354. EB and TH were
  supported by the European Research Council (ERC) under grant HQMAT (Grant Agreement
  No. 817799). A.G. acknowledges support by the European Unions Horizon 2020 research
  and innovation program under the Marie Sklodowska-Curie Grant Agreement\r\nNo. 754411.\r\n"
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Haoxin
  full_name: Zhou, Haoxin
  last_name: Zhou
- first_name: Tian
  full_name: Xie, Tian
  last_name: Xie
- first_name: Areg
  full_name: Ghazaryan, Areg
  id: 4AF46FD6-F248-11E8-B48F-1D18A9856A87
  last_name: Ghazaryan
  orcid: 0000-0001-9666-3543
- first_name: Tobias
  full_name: Holder, Tobias
  last_name: Holder
- first_name: James R.
  full_name: Ehrets, James R.
  last_name: Ehrets
- first_name: Eric M.
  full_name: Spanton, Eric M.
  last_name: Spanton
- first_name: Takashi
  full_name: Taniguchi, Takashi
  last_name: Taniguchi
- first_name: Kenji
  full_name: Watanabe, Kenji
  last_name: Watanabe
- first_name: Erez
  full_name: Berg, Erez
  last_name: Berg
- first_name: Maksym
  full_name: Serbyn, Maksym
  id: 47809E7E-F248-11E8-B48F-1D18A9856A87
  last_name: Serbyn
  orcid: 0000-0002-2399-5827
- first_name: Andrea F.
  full_name: Young, Andrea F.
  last_name: Young
citation:
  ama: Zhou H, Xie T, Ghazaryan A, et al. Half and quarter metals in rhombohedral
    trilayer graphene. <i>Nature</i>. 2021. doi:<a href="https://doi.org/10.1038/s41586-021-03938-w">10.1038/s41586-021-03938-w</a>
  apa: Zhou, H., Xie, T., Ghazaryan, A., Holder, T., Ehrets, J. R., Spanton, E. M.,
    … Young, A. F. (2021). Half and quarter metals in rhombohedral trilayer graphene.
    <i>Nature</i>. Springer Nature. <a href="https://doi.org/10.1038/s41586-021-03938-w">https://doi.org/10.1038/s41586-021-03938-w</a>
  chicago: Zhou, Haoxin, Tian Xie, Areg Ghazaryan, Tobias Holder, James R. Ehrets,
    Eric M. Spanton, Takashi Taniguchi, et al. “Half and Quarter Metals in Rhombohedral
    Trilayer Graphene.” <i>Nature</i>. Springer Nature, 2021. <a href="https://doi.org/10.1038/s41586-021-03938-w">https://doi.org/10.1038/s41586-021-03938-w</a>.
  ieee: H. Zhou <i>et al.</i>, “Half and quarter metals in rhombohedral trilayer graphene,”
    <i>Nature</i>. Springer Nature, 2021.
  ista: Zhou H, Xie T, Ghazaryan A, Holder T, Ehrets JR, Spanton EM, Taniguchi T,
    Watanabe K, Berg E, Serbyn M, Young AF. 2021. Half and quarter metals in rhombohedral
    trilayer graphene. Nature.
  mla: Zhou, Haoxin, et al. “Half and Quarter Metals in Rhombohedral Trilayer Graphene.”
    <i>Nature</i>, Springer Nature, 2021, doi:<a href="https://doi.org/10.1038/s41586-021-03938-w">10.1038/s41586-021-03938-w</a>.
  short: H. Zhou, T. Xie, A. Ghazaryan, T. Holder, J.R. Ehrets, E.M. Spanton, T. Taniguchi,
    K. Watanabe, E. Berg, M. Serbyn, A.F. Young, Nature (2021).
date_created: 2021-09-19T22:01:25Z
date_published: 2021-09-01T00:00:00Z
date_updated: 2023-08-14T07:04:06Z
day: '01'
department:
- _id: MaSe
- _id: MiLe
doi: 10.1038/s41586-021-03938-w
ec_funded: 1
external_id:
  arxiv:
  - '2104.00653'
  isi:
  - '000706977400002'
isi: 1
keyword:
- condensed matter - mesoscale and nanoscale physics
- condensed matter - strongly correlated electrons
- multidisciplinary
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2104.00653
month: '09'
oa: 1
oa_version: Preprint
project:
- _id: 260C2330-B435-11E9-9278-68D0E5697425
  call_identifier: H2020
  grant_number: '754411'
  name: ISTplus - Postdoctoral Fellowships
publication: Nature
publication_identifier:
  eissn:
  - 1476-4687
  issn:
  - 0028-0836
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
  link:
  - relation: erratum
    url: https://doi.org/10.1038/s41586-021-04181-z
scopus_import: '1'
status: public
title: Half and quarter metals in rhombohedral trilayer graphene
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
year: '2021'
...
---
_id: '9928'
abstract:
- lang: eng
  text: 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.
acknowledged_ssus:
- _id: NanoFab
- _id: M-Shop
acknowledgement: We thank W. Hughes for analytic and numerical modeling during the
  early stages of this work, J. Koch for discussions and support with the scqubits
  package, R. Sett, P. Zielinski, and L. Drmic for software development, and G. Katsaros
  for equipment support, as well as the MIBA workshop and the Institute of Science
  and Technology Austria nanofabrication facility. We thank I. Pop, S. Deleglise,
  and E. Flurin for discussions. This work was supported by a NOMIS Foundation research
  grant, the Austrian Science Fund (FWF) through BeyondC (F7105), and IST Austria.
  M.P. is the recipient of a Pöttinger scholarship at IST Austria. E.R. is the recipient
  of a DOC fellowship of the Austrian Academy of Sciences at IST Austria.
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Matilda
  full_name: Peruzzo, Matilda
  id: 3F920B30-F248-11E8-B48F-1D18A9856A87
  last_name: Peruzzo
  orcid: 0000-0002-3415-4628
- first_name: Farid
  full_name: Hassani, Farid
  id: 2AED110C-F248-11E8-B48F-1D18A9856A87
  last_name: Hassani
  orcid: 0000-0001-6937-5773
- first_name: Gregory
  full_name: Szep, Gregory
  last_name: Szep
- first_name: Andrea
  full_name: Trioni, Andrea
  id: 42F71B44-F248-11E8-B48F-1D18A9856A87
  last_name: Trioni
- first_name: Elena
  full_name: Redchenko, Elena
  id: 2C21D6E8-F248-11E8-B48F-1D18A9856A87
  last_name: Redchenko
- first_name: Martin
  full_name: Zemlicka, Martin
  id: 2DCF8DE6-F248-11E8-B48F-1D18A9856A87
  last_name: Zemlicka
- first_name: Johannes M
  full_name: Fink, Johannes M
  id: 4B591CBA-F248-11E8-B48F-1D18A9856A87
  last_name: Fink
  orcid: 0000-0001-8112-028X
citation:
  ama: 'Peruzzo M, Hassani F, Szep G, et al. Geometric superinductance qubits: Controlling
    phase delocalization across a single Josephson junction. <i>PRX Quantum</i>. 2021;2(4):040341.
    doi:<a href="https://doi.org/10.1103/PRXQuantum.2.040341">10.1103/PRXQuantum.2.040341</a>'
  apa: 'Peruzzo, M., Hassani, F., Szep, G., Trioni, A., Redchenko, E., Zemlicka, M.,
    &#38; Fink, J. M. (2021). Geometric superinductance qubits: Controlling phase
    delocalization across a single Josephson junction. <i>PRX Quantum</i>. American
    Physical Society. <a href="https://doi.org/10.1103/PRXQuantum.2.040341">https://doi.org/10.1103/PRXQuantum.2.040341</a>'
  chicago: 'Peruzzo, Matilda, Farid Hassani, Gregory Szep, Andrea Trioni, Elena Redchenko,
    Martin Zemlicka, and Johannes M Fink. “Geometric Superinductance Qubits: Controlling
    Phase Delocalization across a Single Josephson Junction.” <i>PRX Quantum</i>.
    American Physical Society, 2021. <a href="https://doi.org/10.1103/PRXQuantum.2.040341">https://doi.org/10.1103/PRXQuantum.2.040341</a>.'
  ieee: 'M. Peruzzo <i>et al.</i>, “Geometric superinductance qubits: Controlling
    phase delocalization across a single Josephson junction,” <i>PRX Quantum</i>,
    vol. 2, no. 4. American Physical Society, p. 040341, 2021.'
  ista: 'Peruzzo M, Hassani F, Szep G, Trioni A, Redchenko E, Zemlicka M, Fink JM.
    2021. Geometric superinductance qubits: Controlling phase delocalization across
    a single Josephson junction. PRX Quantum. 2(4), 040341.'
  mla: 'Peruzzo, Matilda, et al. “Geometric Superinductance Qubits: Controlling Phase
    Delocalization across a Single Josephson Junction.” <i>PRX Quantum</i>, vol. 2,
    no. 4, American Physical Society, 2021, p. 040341, doi:<a href="https://doi.org/10.1103/PRXQuantum.2.040341">10.1103/PRXQuantum.2.040341</a>.'
  short: M. Peruzzo, F. Hassani, G. Szep, A. Trioni, E. Redchenko, M. Zemlicka, J.M.
    Fink, PRX Quantum 2 (2021) 040341.
date_created: 2021-08-17T08:14:18Z
date_published: 2021-11-24T00:00:00Z
date_updated: 2023-09-07T13:31:22Z
day: '24'
ddc:
- '530'
department:
- _id: JoFi
- _id: NanoFab
- _id: M-Shop
doi: 10.1103/PRXQuantum.2.040341
ec_funded: 1
external_id:
  arxiv:
  - '2106.05882'
  isi:
  - '000723015100001'
file:
- access_level: open_access
  checksum: 36eb41ea43d8ca22b0efab12419e4eb2
  content_type: application/pdf
  creator: cchlebak
  date_created: 2022-01-18T11:29:33Z
  date_updated: 2022-01-18T11:29:33Z
  file_id: '10641'
  file_name: 2021_PRXQuantum_Peruzzo.pdf
  file_size: 4247422
  relation: main_file
  success: 1
file_date_updated: 2022-01-18T11:29:33Z
has_accepted_license: '1'
intvolume: '         2'
isi: 1
issue: '4'
keyword:
- quantum physics
- mesoscale and nanoscale physics
language:
- iso: eng
month: '11'
oa: 1
oa_version: Published Version
page: '040341'
project:
- _id: 26927A52-B435-11E9-9278-68D0E5697425
  call_identifier: FWF
  grant_number: F07105
  name: Integrating superconducting quantum circuits
- _id: 2564DBCA-B435-11E9-9278-68D0E5697425
  call_identifier: H2020
  grant_number: '665385'
  name: International IST Doctoral Program
- _id: 2622978C-B435-11E9-9278-68D0E5697425
  name: Hybrid Semiconductor - Superconductor Quantum Devices
publication: PRX Quantum
publication_identifier:
  eissn:
  - 2691-3399
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
related_material:
  record:
  - id: '13057'
    relation: research_data
    status: public
  - id: '9920'
    relation: dissertation_contains
    status: public
scopus_import: '1'
status: public
title: 'Geometric superinductance qubits: Controlling phase delocalization across
  a single Josephson junction'
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 2
year: '2021'
...