{ "meta": { "api_type": "NWO Projects API", "version": "1.0.2", "licence": { "name": "CC0 1.0 Universal", "url": "https://creativecommons.org/publicdomain/zero/1.0", "description": "To the extent possible under law, all copyright and related or neighbouring rights have been waived worldwide to the data made available through this API." }, "documentation": "https://doi.org/10.5281/zenodo.14918287", "release_date": "2025-08-20T00:00:00", "funder": "https://doi.org/10.13039/501100003246", "ror_id": "https://ror.org/04jsz6e67", "date": "2026-11-05T00:00:00", "count": 1, "per_page": 100, "pages": 1, "page": 1 }, "projects": [ { "project_id": "040.11.707", "title": "Living at the edge: the quantum spin Hall effect in germanene", "funding_scheme_id": 3438, "funding_scheme": "Bezoekersbeurs Bezoekersbeurs 2018 VW", "department": "Sociale en Geesteswetenschappen", "sub_department": "Sociale en Geesteswetenschappen", "start_date": "2019-06-01T00:00:00", "end_date": "2021-11-29T00:00:00", "reporting_year": 2018, "summary_nl": "The quantum spin Hall effect, a novel nontrivial topological quantum state of matter, has been proposed in 2005 for graphene. In contrast to the conventional quantum Hall effect, the quantum spin Hall effect (QSHE) does not require an external magnetic field. The spin-orbit coupling in graphene opens a band gap at the K and K’ points in the Brillouin zone. The spin-orbit gap in graphene is, however, very small (20 eV) and therefore the QSHE in graphene can only be observed at extremely low temperatures (< 0.3 K). Germanene, i.e. the Ge analogue of graphene, has a spin-orbit gap that is 1000 times larger than that of graphene. This means that the QSHE for this two-dimensional material would be observable at experimentally accessible temperatures. The QSHE is characterized by topologically protected gapless helical edges states, whereas the interior of material exhibits an energy gap. The topologically protected edges states are chiral, have a vanishing charge Hall conductance and a quantized spin Hall conductance.\n\nRecently we have successfully synthesized germanene on several substrates. Scanning tunneling spectroscopy of germanene grown on molybdenum disulfide (a band gap material) as well as germanene synthesized on Ge2Pt microcrystals revealed a well-defined V-shaped density of states, which is reminiscent for a 2D Dirac system. Carolien Castenmiller (the PhD student of the NWO FOM16PR3237 project) has studied the electronic properties of the edges of germanene (density of states) as well as the intervalley/intravalley scattering processes at the edges using low-temperature scanning tunneling spectroscopy. \n\nIn addition to a detailed study of the electronic properties of the edges of germanene we also need to scrutinize the electronic properties of the interior –i.e. far away from the edges- of the germanene sheet. This visitor grant proposal deals with a study of the electronic properties of the interior as well as the transition from the interior to the edges of the germanene sheet. In order to go beyond the standard scanning tunneling spectroscopy (IV) measurements we have various tricks on our sleeve. Firstly, we want to determine the exact value of the local work function and its spatial variations from the edge towards the interior of germanene sheets by measuring the field-emission resonances of germanene (also referred to as Gundlach oscillations) using scanning tunneling microscopy. Dr. Bogdana Borca has ample experience with this technique, used for studies on graphene. Secondly, near defects, adsorbates and/or edges we want to perform quasi particle interference measurements in order to extract more information on the spatial variation of the electronic properties in germanene.", "summary_en": "The quantum spin Hall effect, a novel nontrivial topological quantum state of matter, has been proposed in 2005 for graphene. In contrast to the conventional quantum Hall effect, the quantum spin Hall effect (QSHE) does not require an external magnetic field. The spin-orbit coupling in graphene opens a band gap at the K and K’ points in the Brillouin zone. The spin-orbit gap in graphene is, however, very small (20 eV) and therefore the QSHE in graphene can only be observed at extremely low temperatures (< 0.3 K). Germanene, i.e. the Ge analogue of graphene, has a spin-orbit gap that is 1000 times larger than that of graphene. This means that the QSHE for this two-dimensional material would be observable at experimentally accessible temperatures. The QSHE is characterized by topologically protected gapless helical edges states, whereas the interior of material exhibits an energy gap. The topologically protected edges states are chiral, have a vanishing charge Hall conductance and a quantized spin Hall conductance.\n\nRecently we have successfully synthesized germanene on several substrates. Scanning tunneling spectroscopy of germanene grown on molybdenum disulfide (a band gap material) as well as germanene synthesized on Ge2Pt microcrystals revealed a well-defined V-shaped density of states, which is reminiscent for a 2D Dirac system. Carolien Castenmiller (the PhD student of the NWO FOM16PR3237 project) has studied the electronic properties of the edges of germanene (density of states) as well as the intervalley/intravalley scattering processes at the edges using low-temperature scanning tunneling spectroscopy. \n\nIn addition to a detailed study of the electronic properties of the edges of germanene we also need to scrutinize the electronic properties of the interior –i.e. far away from the edges- of the germanene sheet. This visitor grant proposal deals with a study of the electronic properties of the interior as well as the transition from the interior to the edges of the germanene sheet. In order to go beyond the standard scanning tunneling spectroscopy (IV) measurements we have various tricks on our sleeve. Firstly, we want to determine the exact value of the local work function and its spatial variations from the edge towards the interior of germanene sheets by measuring the field-emission resonances of germanene (also referred to as Gundlach oscillations) using scanning tunneling microscopy. Dr. Bogdana Borca has ample experience with this technique, used for studies on graphene. Secondly, near defects, adsorbates and/or edges we want to perform quasi particle interference measurements in order to extract more information on the spatial variation of the electronic properties in germanene.", "award_amount": 5750, "grant_id": "https://doi.org/10.61686/CMFJA70390", "project_members": [ { "role": "Main Applicant", "member_id": 183382, "last_name": "Zandvliet", "degree_pre_nominal": "prof. dr. ir.", "initials": "H.J.W.", "first_name": "Harold", "organisation": "Universiteit Twente||Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS)||MESA+ Research Institute for Nanotechnology", "organisation_id": 62027, "ror": "https://ror.org/006hf6230", "active": true }, { "role": "Project leader", "member_id": 183382, "last_name": "Zandvliet", "degree_pre_nominal": "prof. dr. ir.", "initials": "H.J.W.", "first_name": "Harold", "organisation": "Universiteit Twente||Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS)||MESA+ Research Institute for Nanotechnology", "organisation_id": 62027, "ror": "https://ror.org/006hf6230", "active": true } ], "products": [ { "title": "Spectroscopic signature of surfaces states anc bunching of bulk sub-bands in topological insulator (Bi0.4Sb0.6)2Te3 thin films", "year": 2022, "edition": "105", "start": 35122, "end": 35122, "type": "Wetenschappelijk artikel", "url_open_access": "doi.org/10.1103/PhysRevB.105.035122", "journal_title": "Physical Review B", "authors": [ { "last_name": "Brinkman", "initials": "A.", "role": "Auteur" }, { "last_name": "Castenmiller", "initials": "C.", "role": "Auteur" }, { "last_name": "Witmans", "initials": "F.J.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Mulder", "initials": "L.", "role": "Auteur" }, { "last_name": "Golden", "initials": "M.S.", "role": "Auteur" }, { "last_name": "Boeij", "initials": "P.L.", "prefix": "de", "role": "Auteur" }, { "last_name": "Smit", "initials": "S.", "role": "Auteur" } ] }, { "title": "Image potential states of germanene", "year": 2020, "edition": "7", "start": 35021, "end": 35021, "type": "Wetenschappelijk artikel", "url_open_access": "ttps://doi.org/10.1088/2053-1583/ab96cf", "journal_title": "2D Materials", "authors": [ { "last_name": "Rudenko", "initials": "A.N.", "role": "Auteur" }, { "last_name": "Borca", "initials": "B", "role": "Auteur" }, { "last_name": "Castenmiller", "initials": "C", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Sotthewes", "initials": "K", "role": "Auteur" }, { "last_name": "Tsvetanova", "initials": "M", "role": "Auteur" } ] }, { "title": "Quantum spin Hall states and topological phase transition in germanene", "year": 2023, "edition": "130", "start": 196401, "end": 196401, "type": "Wetenschappelijk artikel", "url_open_access": "doi.org/10.1103/PhysRevLett.130.196401", "journal_title": "Physical Review Letters", "authors": [ { "last_name": "Rudenko", "initials": "A.N.", "role": "Auteur" }, { "last_name": "Castenmiller", "initials": "C", "role": "Auteur" }, { "last_name": "Liu", "initials": "C.-C.", "role": "Auteur" }, { "last_name": "KLaassen", "initials": "D.J.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Mil", "initials": "J", "prefix": "van", "role": "Auteur" }, { "last_name": "Ezawa", "initials": "M.", "role": "Auteur" }, { "last_name": "Bampoulis", "initials": "P", "role": "Auteur" }, { "last_name": "Liu", "initials": "Y", "role": "Auteur" }, { "last_name": "Yao", "initials": "Y.", "role": "Auteur" } ] }, { "title": "Charge localization induced by pentagons on Ge(110)", "year": 2023, "edition": "127", "start": 599, "end": 605, "type": "Wetenschappelijk artikel", "url_open_access": "doi.org/10.1021/acs.jpcc.2c06399", "journal_title": "Jounral of Phys. Chem. C", "authors": [ { "last_name": "Castenmiller", "initials": "C.", "role": "Auteur" }, { "last_name": "KLaassen", "initials": "D.J.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Bampoulis", "initials": "P.", "role": "Auteur" } ] }, { "title": "Dual modulation STM:\nSimultaneous high resolution mapping of the differential conductivity and local tunnel barrier height\ndemonstrated on Au(111)", "sub_title": "Simultaneous high resolution mapping of the differential conductivity and local tunnel barrier height\n\ndemonstrated on Au(111)", "year": 2021, "edition": "129", "start": 225301, "end": 225301, "type": "Wetenschappelijk artikel", "url_open_access": "doi.org/10.1063/5.0051403", "journal_title": "Journal of Applied Physics", "authors": [ { "last_name": "Castenmiller", "initials": "C.", "role": "Auteur" }, { "last_name": "Witmans", "initials": "F.J.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Sturm", "initials": "J.M.", "role": "Auteur" }, { "last_name": "Sotthewes", "initials": "K.", "role": "Auteur" }, { "last_name": "Ackermann", "initials": "M.D.", "role": "Auteur" }, { "last_name": "Siekman", "initials": "M.H.", "role": "Auteur" }, { "last_name": "Boeij", "initials": "P.L.", "prefix": "de", "role": "Auteur" }, { "last_name": "Oldenkotte", "initials": "V.J.S.", "role": "Auteur" } ] }, { "title": "Combined I(V) and dI(V)/dz scanning tunneling spectroscopy", "year": 2018, "edition": "8", "start": 75013, "end": 75013, "type": "Wetenschappelijk artikel", "url_open_access": "doi.org/10.1063/1.5034422", "journal_title": "AIP ADVANCES", "authors": [ { "last_name": "Castenmiller", "initials": "C.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" }, { "last_name": "Sotthewes", "initials": "K.", "role": "Auteur" }, { "last_name": "Siekman", "initials": "M.H.", "role": "Auteur" }, { "last_name": "Bremen", "initials": "R.", "prefix": "van", "role": "Auteur" } ] }, { "title": "On the mystery of the absence of a spin-orbit gap in scanning\ntunneling microscopy spectra of germanene", "year": 2020, "edition": "41", "start": 82003, "end": 82003, "type": "Wetenschappelijk artikel", "url_open_access": "doi: 10.1088/1674-4926/41/8/082003", "journal_title": "Journal of Semiconductors", "authors": [ { "last_name": "Castenmiller", "initials": "C.", "role": "Auteur" }, { "last_name": "Zandvliet", "initials": "H.J.W.", "role": "Auteur" } ] } ] } ] }