Publications

Group highlights

(For a full list see below or go to Google Scholar, ResearcherID)

Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc

We use our atomic-scale scanning tunneling noise setup on a disordered superconductor, and discover a state above TC that, much like an ordinary metal, has no (pseudo)gap, but carries charge via paired electrons.

KM Bastiaans, D Chatzopoulos, J-F Ge, D Cho, WO Tromp, JM van Ruitenbeek, MH Fischer, PJ de Visser, DJ Thoen, EFC Driessen, TM Klapwijk, MP Allan

arXiv:2101.08535 (2021)

Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45

We report on a peculiar, spatially dispersing YSR state in Fe(Se,Te) that can be tuned by the tip.

D Chatzopoulos, Doohee Cho, KM Bastiaans, GO Steffensen, D Bouwmeester, A Akbari, Genda Gu, J Paaske, BM Andersen, MP Allan

Nature Communications 12, 298 (2021)

Mapping local heterogeneity in open twisted bilayer graphene devices

Why is there so much variation in TBG devices? And are open devices more disordered than encapsulated ones? We introduce a new method to continuously map inhomogeneities of a moiré lattice and apply it to open-device TBG to show that twist angle variation is small over areas of hundreds of nm.

T Benschop, TA de Jong, P Stepanov*, Xiaobo Lu, V Stalman, SJ van der Molen, DK Efetov, MP Allan

arXiv:2008.13766 (2020)

Observation of flat bands in twisted bilayer graphene

A first paper from the TBG collaboration is online, with beautiful data from the Baumberger group in Geneva, and great devices from the Efetov group at ICFO. We measured STM on the device.

S Lisi, X Lu, T Benschop, TA de Jong, Petr S, JR Duran, F Margot, I Cucchi, E Cappelli, A Hunter, A Tamai, V Kandyba, A Giampietri, A Barinov, J Jobst, V Stalman, M Leeuwenhoek, K Watanabe, T Taniguchi, L Rademaker, SJ van der Molen, MP Allan, DK Efetov, F Baumberger

Nature Physics (2020)

News coverage by NRC

A strongly inhomogeneous superfluid in an iron-based superconductor

We succeeded in measuring the superfluid density with atomic resolution on an unconventional superconductor! In contrast to expectations for conventional superconductors, we find that the superfluid densisty is strongly inhomogeneous in FeTe0.55Se0.45.

D Cho* & KM Bastiaans* & D Chatzopoulos*, GD Gu, MP Allan

Nature 571, 541 (2019)

Nanofabricated tips as a platform for double-tip and device based scanning tunneling microscopy

We introduce a platform for bringing new, device-based functionality to STM, with the goal of utilizing decades of progress in device engineering for the field of scanning probe.

M Leeuwenhoek, RA Norte, KM Bastiaans, Doohee Cho, I Battisti, YaM Blanter, S Gröblacher, MP Allan

Nanotechnology 30, 335702 (2019)

See also our papers on the theoretical modeling of such measurements, and the paper about fabrication.

 

Full List

  1. Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc
    KM Bastiaans, D Chatzopoulos, J-F Ge, D Cho, WO Tromp, JM van Ruitenbeek, MH Fischer, PJ de Visser, DJ Thoen, EFC Driessen, TM Klapwijk, MP Allan
    arXiv:2101.08535 (2021)

  2. Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe0.55Se0.45
    D Chatzopoulos, Doohee Cho, KM Bastiaans, GO Steffensen, D Bouwmeester, A Akbari, Genda Gu, J Paaske, BM Andersen, MP Allan
    Nature Communications 12, 298 (2021)

  3. Multi-Atom Quasiparticle Scattering Interference for Superconductor Energy-Gap Symmetry Determination
    R Sharma, A Kreisel, MA Sulangi, J Böker, A Kostin, MP Allan, H Eisaki, AE Böhmer, PC Canfield, I Eremin, JC Davis, PJ Hirschfeld, PO Sprau
    npj Quantum Mater. 6, 7 (2021)

  4. Mapping local heterogeneity in open twisted bilayer graphene devices
    T Benschop, TA de Jong, P Stepanov*, Xiaobo Lu, V Stalman, SJ van der Molen, DK Efetov, MP Allan
    arXiv:2008.13766 (2020)

  5. Direct comparison of ARPES, STM, and quantum oscillation data for band structure determination in Sr2RhO4
    I Battisti, WO Tromp, S Riccò, RS Perry, AP Mackenzie, A Tamai, F Baumberger, MP Allan
    npj Quantum Materials 5, 91 (2020)

  6. Fabrication of on-chip probes for double-tip scanning tunneling microscopy
    M Leeuwenhoek, F Groenewoud, K van Oosten, T Benschop, MP Allan, S Gröblacher
    Microsyst Nanoeng 6, 99 (2020)

  7. Modeling Green’s functions measurements with two-tip scanning tunneling microscopy
    M Leeuwenhoek, S Gröblacher, MP Allan, YaM Blanter
    PRB 102, 115416 (2020)

  8. Observation of flat bands in twisted bilayer graphene
    S Lisi, X Lu, T Benschop, TA de Jong, Petr S, JR Duran, F Margot, I Cucchi, E Cappelli, A Hunter, A Tamai, V Kandyba, A Giampietri, A Barinov, J Jobst, V Stalman, M Leeuwenhoek, K Watanabe, T Taniguchi, L Rademaker, SJ van der Molen, MP Allan, DK Efetov, F Baumberger
    Nature Physics (2020)

  9. A strongly inhomogeneous superfluid in an iron-based superconductor
    D Cho* & KM Bastiaans* & D Chatzopoulos*, GD Gu, MP Allan
    Nature 571, 541 (2019)

  10. Nanofabricated tips as a platform for double-tip and device based scanning tunneling microscopy
    M Leeuwenhoek, RA Norte, KM Bastiaans, Doohee Cho, I Battisti, YaM Blanter, S Gröblacher, MP Allan
    Nanotechnology 30, 335702 (2019)

  11. Imaging doubled shot noise in a Josephson scanning tunneling microscope
    KM Bastiaans, D Cho, D Chatzopoulos, M Leeuwenhoek, C Koks, MP Allan
    Phys. Rev. B 100, 104506 (2019)

  12. Definition of design guidelines, construction and performance of an ultra-stable scanning tunneling microscope for spectroscopic imaging
    I Battisti, G Verdoes, K van Oosten, KM Bastiaans, and MP Allan
    Rev. Sci. Instrum. 89, 123705 (2018)

  13. Charge trapping and super-Poissonian noise centres in a cuprate superconductor
    KM Bastiaans* & D Cho*, T Benschop, I Battisti, Y Huang, MS Golden, Q Dong, Y Jin, J Zaanen, MP Allan
    Nature Physics 14, 1183 (2018)

  14. Amplifier for scanning tunneling microscopy at MHz frequencies
    KM Bastiaans, T Benschop, D Chatzopoulos, D Cho, Q Dong, Y Jin, MP Allan
    Rev. Sci. Instrum. 89, 093709 (2018)

  15. Revisiting quasiparticle scattering interference in high-temperature superconductors: the problem of narrow peaks
    MA Sulangi, MP Allan, J Zaanen
    PRB 96, 134507 (2017)

  16. Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips
    S Tewari, KM Bastiaans, MP Allan, JM van Ruitenbeek
    Beilstein J. Nanotechnol. 8, 2389 (2017)

  17. Creating better superconductors by periodic nanopatterning
    MP Allan, MH Fischer, O Ostojic, A Andringa
    SciPost Phys. 3, 010 (2017)

  18. Poor electronic screening in lightly doped Mott insulators observed with scanning tunneling microscopy
    I Battisti, V Fedoseev, KM Bastiaans, A de la Torre, RS Perry, F Baumberger, MP Allan
    Phys. Rev. B 95, 235141, Editors’ suggestion (2017)

  19. Universality of pseudo gap and emergent order in lightly doped Mott insulators
    I. Battisti* & K.M. Bastiaans*, V. Fedoseev, A. de la Torre, N. Iliopoulos, A. Tamai, E.C. Hunter, R.S. Perry, J. Zaanen, F. Baumberger, M.P. Allan
    Nature Physics 13, 21 (2017)

  20. Identifying the fingerprint of antiferromagnetic spin fluctuations in iron pnictide superconductors
    MP Allan* & Kyungmin Lee* & AW Rost*, MH Fischer, F Massee, K Kihou, C-H Lee, A Iyo, H Eisaki, T-M Chuang, AP Mackenzie, JC Davis, DJ Scalapino, E-A Kim
    Nature Physics 11, 177 (2015)

  21. Direct evidence for a magnetic f-electron mediated Cooper pairing mechanism of heavy fermion superconductivity in CeCoIn5
    J Van Dyke, F Massee, MP Allan, JC Davis, C Petrovic, and DK Morr
    PNAS 111, 11663 (2014)

  22. Imaging Cooper pairing of heavy fermions in CeCoIn5
    MP Allan* & F Massee*, DK Morr, J van Dyke, AW Rost, AP Mackenzie, C Petrovic, JC Davis
    Nature Physics 9, 468 (2013)

  23. Formation of heavy d-electron quasiparticles in Sr3Ru2O7
    MP Allan, A Tamai, E Rozbicki, MH Fischer, J Voss, PDC King, W Meevasana, S Thirupathaiah, E Rienks, J Fink, A Tennant, RS Perry, JF Mercure, MA Wang, J Lee, CJ Fennie, E-A Kim, MJ Lawler, KM Shen, AP Mackenzie, Z-X Shen, F Baumberger
    New Journal of Physics 15, 063029 (2013)

  24. Anisotropic impurity states, quasiparticle scattering and nematic transport in underdoped Ca(Fe1−xCox)2As2
    MP Allan, T-M Chuang, F Massee, Y Xie, N Ni, SL Bud’ko, GS Boebinger, Q Wang, DS Dessau, PC Canfield, MS Golden, JC Davis
    Nature Physics 9, 220 (2013)

  25. Anisotropic energy gaps of iron-based superconductivity from intraband quasiparticle interference in LiFeAs
    MP Allan⋆ & AW Rost⋆, AP Mackenzie, Y Xie, JC Davis, K Kihou, CH Lee, A Iyo, H Eisaki, T-M Chuang
    Science 336, 563 (2012)

  26. How Kondo-holes create intense nanoscale heavy-fermion hybridization disorder
    MH Hamidian, AR Schmidt, IA Firmo, MP Allan, P Bradley, JD Garrett, TJ Williams, GM Luke, Y Dubi, AV Balatsky, JC Davis
    PNAS 108, 18233 (2011)

  27. Nematic electronic structure in the “parent” state of the iron-based superconductor Ca(Fe1−xCox)2As2
    T-M Chuang* & MP Allan*, J Lee, Y Xie, N Ni, SL Bud’ko, GS Boebinger PC Canfield, JC Davis
    Science 327, 181 (2010)

  28. Heavy d-electron quasiparticle interference and real-space electronic structure of Sr3Ru2O7
    Jinho Lee* & M. P. Allan*, M. A.Wang, J. Farrell, S. A. Grigera, F. Baumberger, J. C. Davis and A. P. Mackenzie
    Nature Physics 5, 800 (2009)

  29. Fermi surface and van Hove singularities in the itinerant metamagnet Sr3Ru2O7
    A Tamai, MP Allan, JF Mercure, W Meevasana, R Dunkel, DH Lu, RS Perry, AP Mackenzie, David J Singh, Z-X Shen, F Baumberger
    Phys. Rev. Lett. 101, 026407 (2008)

  30. Tunable self-assembly of one-dimensional nanostructures with orthogonal directions
    MP Allan, S Berner, M Corso, T Greber, J Osterwalder
    Nanoscale Research Letters 2, 94 (2007)

  31. Photoelectron Diffraction for a Look inside Nanostructures
    J Osterwalder, A Tamai, W Auwärter; MP Allan, T Greber
    CHIMIA 11, 759 (2006)