Facilities
Large-scale facilities

APE Low-Energy

General informations

Location
Trieste, Elettra Synchrotron light source
Main techniques and methods
ARPES, Spin-ARPES, PLD, STM-STS
Key instumentation
- Scienta-Omicron DA30 ARPES analyzer
- VESPA integrated spin ARPES polarimeter
- beamline APE-LE (variable photon polarization: 8-90 eV photon energy range)
- home-built PLD
- home-built STM

APE-LE is a beamline within Elettra dedicated to high resolution angle-resolved photoemission spectroscopy (ARPES) with Spin-resolution (Spin-ARPES), and thus employed in the investigation of electronic and spin properties of highly correlated electronic systems.

APE-LE is part of the APE-NFFA complex that is based on a state-of-the-art surface science laboratory as a support facility for advanced spectroscopies at two distinct beamline end-stations (APE-LE and APE-HE) using polarized synchrotron radiation in the ultraviolet and soft X-ray range from the Elettra storage ring.

Technical description

APE-LE is part of the APE-NFFA complex (http://trieste.nffa.eu/) that is based on a state-of-the-art surface science laboratory as a support facility for advanced spectroscopies at two distinct beamlines (APE-LE and APE-HE) using polarized synchrotron radiation in the ultraviolet and soft X-ray range from the Elettra storage ring. The sample preparation and survey represent crucial and integral part of our experiments. For this reason the interconnected set of UHV chambers within the APE-NFFA complex allows for state-of-the-art sample growth by in situ pulsed laser deposition (PLD),  advanced surface preparation (Ar ion sputtering, annealing, controlled evaporation, LEED/Auger characterization, Kerr magnetometry) and characterization by atomic resolution scanning tunneling microscope (STM) and also by XPS/XAS (at APE-HE), prior to spectroscopic studies of the electronic band structures and related spin textures (ARPES and Spin-ARPES).

Detailed technical description of all apparatuses operating within APE-LE (ARPES / Spin ARPES, PLD, Surface and Nano Science Lab and STM/S facilities) are available at:

http://trieste.nffa.eu/areas/spectroscopy/arpes-and-spin-arpes/; http://trieste.nffa.eu/areas/growth/pld/;

http://trieste.nffa.eu/areas/characterization/surface-and-nano-science-lab/;

http://trieste.nffa.eu/areas/characterization/stmsts/.

Development of new methods, instrumentation, software

APE-LE hosts VESPA, a unique facility for Spin-ARPES at Elettra, fully developed, built and commissioned within NFFA. Its operation is based on the exchange coupling between the photoelectron spin and a ferromagnetic target in a reflectometry setup (VLEED concept). VESPA is integrated with a dedicated Scienta-Omicron DA30 ARPES analyzer allowing for distinct measurements over the selected Brillouin zone areas that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the corresponding spin texture. The discovery of new topological phases characterized by peculiar spin textures contributed to the extremely high request for Spin-ARPES (APE-LE oversubscription ratio ~4).

A second PLD chamber is currently being developed at APE-LE. It will be optimized for deposition of metallic layers (Nd:YAG as opposed to present KrF excimer, currently adapted to oxides and semimetallic (topological) materials). The second PLD will be UHV connected to the rest of the APE complex through also in-house developed and built UHV transfer system.

Research Activity

The research at the APE-LE beamline exploits angle resolved photoemission (ARPES) and ARPES with spin resolution (Spin-ARPES) in the investigation of electronic properties of materials, in particular the electronic band structures, related spin textures, Fermi surfaces and Fermi surface instabilities. APE-LE is dedicated to the investigation of highly correlated electronic systems, spintronic materials: topological insulators and systems with strong spin-orbit interaction in general, transition metal oxides, low-dimensional electronic systems, superconducting materials, surfaces, molecular films on solid surfaces and magnetic materials. Recently developed in-situ PLD facility (and also UHV transfer through a vacuum suitcase from oxide MBE)  allows us to investigate the materials where the electronic properties are finely tuned through material nano-engineering. The research at APE-LE is further substantiated by the complementary in-situ STM characterization of the surface structural and electronic properties.

All APE-LE facilities have been implemented with the support of the NFFA research infrastructure projects that aim at continuously developing and operating an integrated users access infrastructure along with APE-HE, NFFA-SPRINT and with partial involvement of other IOM (S/TEM, MBE-nanowires) and SPIN (PLD, Theory) activities, using dedicated resources from national and EU grants under the responsibility and coordination of Giorgio Rossi (Università di Milano and IOM-CNR).

Projects

MIUR-FOE, NFFA , 2013-present
MIUR, Eurofel-APE (former Ab Nanotech), 2014-present

ICTP TRIL PROGRAM, ICTP, 2016-present

Main collaborations

  • CNR-SPIN, Chieti
  • Politecnico di Milano
  • University of St. Andrews, UK
  • Princeton University, USA
  • University of Wuerzburg, Germany

Key publications

Physical Review Letters, 125-21, 2020 doi:10.1103/PhysRevLett.125.216402

Radial Spin Texture of the Weyl Fermions in Chiral Tellurium

Gatti G., Gosálbez-Martínez D., Tsirkin S.S., Fanciulli M., Puppin M., Polishchuk S., Moser S., Testa L., Martino E., Roth S., Bugnon P., Moreschini L., Bostwick A., Jozwiak C., Rotenberg E., Di Santo G., Petaccia L., Vobornik I., Fujii J., Wong J., Jariwala D., Atwater H.A., Rønnow H.M., Chergui M., Yazyev O.V., Grioni M., Crepaldi A.
Advanced Functional Materials, 30-22, 2020 doi:10.1002/adfm.202000915

Transition-Metal Dichalcogenide NiTe<inf>2</inf>: An Ambient-Stable Material for Catalysis and Nanoelectronics

Nappini S., Boukhvalov D.W., D'Olimpio G., Zhang L., Ghosh B., Kuo C.-N., Zhu H., Cheng J., Nardone M., Ottaviano L., Mondal D., Edla R., Fuji J., Lue C.S., Vobornik I., Yarmoff J.A., Agarwal A., Wang L., Zhang L., Bondino F., Politano A.
Physical Review Materials, 4-2, 2020 doi:10.1103/PhysRevMaterials.4.025801

Distinct behavior of localized and delocalized carriers in anatase TiO2 (001) during reaction with O2

Bigi C., Tang Z., Pierantozzi G.M., Orgiani P., Das P.K., Fujii J., Vobornik I., Pincelli T., Troglia A., Lee T.-L., Ciancio R., Drazic G., Verdini A., Regoutz A., King P.D.C., Biswas D., Rossi G., Panaccione G., Selloni A.
Physical Review Materials, 4-2, 2020 doi:10.1103/PhysRevMaterials.4.025006

Direct insight into the band structure of SrNbO3

Bigi C., Orgiani P., Sławińska J., Fujii J., Irvine J.T., Picozzi S., Panaccione G., Vobornik I., Rossi G., Payne D., Borgatti F.
Nature Communications, 10-1, 2019 doi:10.1038/s41467-019-13464-z

Weyl-like points from band inversions of spin-polarised surface states in NbGeSb

Marković I., Hooley C.A., Clark O.J., Mazzola F., Watson M.D., Riley J.M., Volckaert K., Underwood K., Dyer M.S., Murgatroyd P.A.E., Murphy K.J., Fèvre P.L., Bertran F., Fujii J., Vobornik I., Wu S., Okuda T., Alaria J., King P.D.C.
Nano Letters, 18-5:2751-2758, 2018 doi:10.1021/acs.nanolett.7b04829

Ferroelectric Control of the Spin Texture in GeTe

Rinaldi C., Varotto S., Asa M., Sławińska J., Fujii J., Vinai G., Cecchi S., Di Sante D., Calarco R., Vobornik I., Panaccione G., Picozzi S., Bertacco R.
Nature Materials, 17-1:21-27, 2018 doi:10.1038/NMAT5031

Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides

Bahramy M.S., Clark O.J., Yang B.-J., Feng J., Bawden L., Riley J.M., Markovic I., Mazzola F., Sunko V., Biswas D., Cooil S.P., Jorge M., Wells J.W., Leandersson M., Balasubramanian T., Fujii J., Vobornik I., Rault J.E., Kim T.K., Hoesch M., Okawa K., Asakawa M., Sasagawa T., Eknapakul T., Meevasana W., King P.D.C.
Nature, 549-7673:492-496, 2017 doi:10.1038/nature23898

Maximal Rashba-like spin splitting via kinetic-energy-coupled inversion-symmetry breaking

Sunko V., Rosner H., Kushwaha P., Khim S., Mazzola F., Bawden L., Clark O.J., Riley J.M., Kasinathan D., Haverkort M.W., Kim T.K., Hoesch M., Fujii J., Vobornik I., Mackenzie A.P., King P.D.C.
Journal of Synchrotron Radiation, 24-4:750-756, 2017 doi:10.1107/S1600577517006907

Very efficient spin polarization analysis (VESPA): New exchange scattering-based setup for spin-resolved ARPES at APE-NFFA beamline at Elettra

Bigi C., Das P.K., Benedetti D., Salvador F., Krizmancic D., Sergo R., Martin A., Panaccione G., Rossi G., Fujii J., Vobornik I.
Nature Communications, 7, 2016 doi:10.1038/ncomms10847

Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe<inf>2</inf>

Das P.K., Di Sante D., Vobornik I., Fujii J., Okuda T., Bruyer E., Gyenis A., Feldman B.E., Tao J., Ciancio R., Rossi G., Ali M.N., Picozzi S., Yadzani A., Panaccione G., Cava R.J.