Publications

Gianmarco Gatti, Christophe Berthod, Julia Issing, Michael Straub, Salony Mandloi, Yann Alexanian, J. Avila, P. Dudin, T. K. Kim, M. D. Watson, C. Cacho, K. Watanabe, T. Taniguchi, W. Wang, N. Clark, R. Gorbachev, Nicolas Ubrig, Ignacio Gutierrez Lezama, Alberto Morpurgo, Anna Tamai and Felix Baumberger

Preprint (2026)

Many-body interactions can couple electronic states in one layer with collective excitations in the adjacent layer, providing a route to tailor properties of heterostructures. However, detecting and quantifying interlayer many-body interactions proved a major challenge. Here, we demonstrate that…

Michael Straub

Thèse, 113 (2026)

Recent advances in microfocused angle-resolved photoemission (micro-ARPES) enable the investigation of momentum-resolved electronic structure on micron length scales. This thesis uses these capabilities to study three different quantum materials: bulk 1T-TaSe₂, strained…

Honey Boban, Tanguy François Jean Prongué, Amarjyoti Choudhury, Dario Marchiani, Andres Felipe Bareño Prieto, Félix Eder, Enrico Giannini, Fabian von Rohr, Alberto Morpurgo, Marco Gibertini, Anna Tamai and Felix Baumberger

Preprint (2026)

Recent transport experiments reported a quantum spin Hall insulator phase in monolayer 1T-TaIrTe₄ gated away from charge neutrality. This phase is not predicted by band structure calculations and has been attributed to an electronic instability induced by strong correlations at a…

Salony Mandloi

Thèse (2026)

Two-dimensional Janus transition metal dichalcogenides are a unique class of materials with broken inversion symmetry and an intrinsic electric field across the layer. In this thesis, we investigate RhSeCl, a newly synthesized Janus semiconductor with exceptionally low chalcogen mixing. Using…

Yann Alexanian, A. de la Torre, Siobhan Mckeown Walker, Michael Straub, Gianmarco Gatti, Andrew Scott Hunter, Salony Mandloi, Edoardo Cappelli, Sara Ricco, Flavio Yair Bruno, M. Radovic, N. C. Plumb, M. Shi, J. Osiecki, C. Polley, T. K. Kim, P. Dudin, M. Hoesch, R. S. Perry, Anna Tamai and Felix Baumberger

npj quantum materials 10, 100 (2025)

The fate of the Fermi surface in bulk electron-doped Sr$_{2}$IrO$_{4}$ remains elusive, as does the origin and extension of its pseudogap phase. Here, we use high-resolution angle-resolved photoelectron spectroscopy (ARPES) to investigate the electronic structure of Sr$_{2-x}$La$_{x}$IrO$_{4}$ up…

Michael Straub, Francesco Petocchi, Catherine Witteveen, F. B. Kugler, Andrew Scott Hunter, Yann Alexanian, Gianmarco Gatti, Salony Mandloi, C. Polley, G. Carbone, J. Osiecki, Fabian von Rohr, Antoine Georges, Felix Baumberger and Anna Tamai

Physical review letters 135, 096501 (2025)

We study the electronic structure of bulk 1T-TaSe$_2$ in the charge density wave phase at low temperature. Our spatially and angle resolved photoemission (ARPES) data show insulating areas coexisting with metallic regions characterized by a chiral Fermi surface and moderately correlated…

Sandy Adhitia Ekahana, Satoshi Okamoto, Jan Dreiser, Loïc Roduit, Igor Plokhikh, Dariusz Jakub Gawryluk, Andrew Scott Hunter, Anna Tamai and Yona Soh

Communications materials 6 1, 235 (2025)

Co₃ Sn₂ S₂ has been reported to be a Weyl semimetal with c -axis ferromagnetism below a Curie temperature of 177 K. Despite the large interest in Co₃ Sn₂ S₂ , the magnetic structure is still unclear. Recent studies have challenged…

Andrew Scott Hunter, C. Putzke, F. B. Kugler, S. Beck, Edoardo Cappelli, Florian Margot, Michael Straub, Yann Alexanian, Jérémie Teyssier, A. de la Torre, K. W. Plumb, M. D. Watson, T. K. Kim, C. Cacho, N. C. Plumb, M. Shi, M. Radovic, J. Osiecki, C. Polley, D. A. Sokolov, A. P. Mackenzie, E. Berg, Antoine Georges, P. J. W. Moll, Anna Tamai and Felix Baumberger

Preprint (2025)

Interacting electrons can form metallic states beyond the Fermi liquid paradigm, a conceptual frontier of many-body physics mainly explored via bulk thermodynamics and transport. In contrast, the microscopics of anomalous single-particle excitations underlying non-Fermi liquid properties have…

Julia Issing

Thèse (2024)

Thinning a bulk material down to a few atomic layers or even to a monolayer influences its physical properties considerably. Such two-dimensional materials can also be used to engineer new correlated phases by stacking them on top of each other. In the present thesis, I present my work on twisted…

Andrew Scott Hunter, C. Putzke, Iaroslav Gaponenko, Anna Tamai, Felix Baumberger and P. J. W. Moll

Review of scientific instruments 95, 033905 (2024)

Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). Both require atomically clean and flat crystal surfaces…

Sandy Adhitia Ekahana, Y. Soh, Anna Tamai, Daniel Gosálbez-Martínez, Mengyu Yao, Andrew Scott Hunter, Wenhui Fan, Yihao Wang, Junbo Li, Armin Kleibert, C. A. F. Vaz, Junzhang Ma, Yimin Xiong, Oleg V. Yazyev, Felix Baumberger, Ming Shi and Gabriel Aeppli

Nature 627, 67-72 (2024)

Ordinary metals contain electron liquids within well-defined ‘Fermi’ surfaces at which the electrons behave as if they were non-interacting. In the absence of transitions to entirely new phases such as insulators or superconductors, interactions between electrons induce scattering that is…

Florian Margot

Thèse, 136 (2023)

2D semiconducting materials represent an interesting opportunity for the desired scaling of electronic devices. Black phosphorus (PB) is a promising candidate because of its direct gap in the range of telecommunications wavelengths and a comparatively high room-temperature mobility that compares…

Sandy Adhitia Ekahana, Genta Indra Winata, Y. Soh, Anna Tamai, Milan Radovic, Gabriel Aeppli and Ming Shi

Machine learning: science and technology (2023)

There is a growing recognition that electronic band structure is a local property of materials and devices, and there is steep growth in capabilities to collect the relevant data. New photon sources, from small-laboratory-based lasers to free electron lasers, together with focussing beam optics and …

Florian Margot, Simone Lisi, Irène Cucchi, Edoardo Cappelli, Andrew Scott Hunter, Ignacio Gutierrez Lezama, KeYuan Ma, Fabian von Rohr, Christophe Berthod, Francesco Petocchi, Samuel Poncé, Nicola Marzari, Marco Gibertini, Anna Tamai, Alberto Morpurgo and Felix Baumberger

Nano letters 23, 6433 (2023)

Black phosphorus (BP) stands out among two-dimensional (2D) semiconductors because of its high mobility and thickness dependent direct band gap. However, the quasiparticle band structure of ultrathin BP has remained inaccessible to experiment thus far. Here we use a recently developed laser-based…

Andrew Scott Hunter, S. Beck, Edoardo Cappelli, Florian Margot, Michael Straub, Yann Alexanian, Gianmarco Gatti, M. D. Watson, T. K. Kim, C. Cacho, N. C. Plumb, M. Shi, M. Radović, D. A. Sokolov, A. P. Mackenzie, M. Zingl, J. Mravlje, Antoine Georges, Felix Baumberger and Anna Tamai

Physical review letters 131, 236502 (2023)

We study the temperature evolution of quasiparticles in the correlated metal Sr$_2$RuO$_4$. Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200~K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy we demonstrate that the…

Andrew Scott Hunter

Thèse (2023)

In its normal state, Sr₂RuO₄ is a prototypical Fermi liquid below ∼ 25 K. At ∼ 1.5 K it undergoes a superconducting transition, but it has long remained challenging to determine the symmetry or order parameter of the superconducting state. Recent experiments have shown…

Gianmarco Gatti, Julia Issing, Louk Rademaker, Florian Margot, Tobias A. de Jong, Sense Jan van der Molen, Jérémie Teyssier, Timur K. Kim, Matthew D. Watson, Cephise Cacho, Pavel Dudin, José Avila, Kumara Cordero Edwards, Patrycja Paruch, Nicolas Ubrig, Ignacio Gutierrez Lezama, Alberto Morpurgo, Anna Tamai and Felix Baumberger

Physical review letters 131 4, 046401 (2023)

The recent observation of correlated phases in transition metal dichalcogenide moir\’e systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space…

Siobhan Mckeown Walker, Margherita Boselli, Emanuel A. Martínez, Stefano Gariglio, Flavio Y. Bruno and Felix Baumberger

Advanced electronic materials, 2101376 (2022)

We have measured the electronic structure of the two-dimensional electron system (2DES) found at the Al/SrTiO3 (Al/STO) and LaAlO3/SrTiO3 (LAO/STO) interfaces by means of laser angle resolved photoemission spectroscopy, taking advantage of the large photoelectron escape depth at low photon energy…

M. Caputo, J. Jandke, Edoardo Cappelli, S.K. Chaluvadi, E. Bonini Guedes, M. Naamneh, G. Vinai, J. Fujii, P. Torelli, I. Vobornik, A. Goldoni, P. Orgiani, Felix Baumberger, M. Radovic and G. Panaccione

Applied surface science 574, 151608 (2022)

Edoardo Cappelli, A. Hampel, A. Chikina, E. Bonini Guedes, Gianmarco Gatti, Andrew Scott Hunter, Julia Issing, N. Biskup, M. Varela, Cyrus E. Dreyer, Anna Tamai, Antoine Georges, F. Y. Bruno, M. Radovic and Felix Baumberger

Physical review materials 6, 075002 (2022)

We use angle-resolved photoemission to map the Fermi surface and quasiparticle dispersion of bulk-like thin films of SrMoO$_3$ grown by pulsed laser deposition. The electronic self-energy deduced from our data reveals weak to moderate correlations in SrMoO$_3$, consistent with our observation of…

Xiang Li, S. E. Cooper, A. Krishnadas, A. de la Torre, R. S. Perry, Felix Baumberger, D. M. Silevitch, D. Hsieh, T. F. Rosenbaum and Yejun Feng

Physical review. B. 104 20, L201111 (2021)

Edoardo Cappelli

Thèse (2021)

In this thesis, I present my research work on epitaxial thin films of LaNiO3 and SrMoO3, investigated by angle-resolved photoemission spectroscopy (ARPES), which yields a direct measurement of the interacting electronic structure. Thin films of the correlated transition-metal oxide LaNiO3 undergo a …

Irène Cucchi, Simone Lisi, Florian Margot, Hugo Henck, Anna Tamai and Felix Baumberger

Comptes rendus. Physique. 22 S4 (2021)

L. S. I. Veiga, M. Etter, Edoardo Cappelli, H. Jacobsen, J. G. Vale, C. D. Dashwood, D. Le, Felix Baumberger, D. F. McMorrow and R. S. Perry

Physical review materials 4 9, 094202 (2020)

Irène Cucchi

Thèse (2020)

Van der Waals materials can be exfoliated down to atomically thin crystals, offering potential to explore physics in lower dimensionality. In this thesis, I investigated their topological electronic structure with ARPES. I studied mono-, bi- and few-layer Td-WTe2. The small size of exfoliated…

I. Battisti, W. O. Tromp, Sara Ricco, R. S. Perry, A. P. Mackenzie, Anna Tamai, Felix Baumberger and M. P. Allan

npj Quantum Materials 5 1, 91 (2020)

Discrepancies in the low-energy quasiparticle dispersion extracted from angle-resolved photoemission, scanning tunneling spectroscopy, and quantum oscillation data are common and have long haunted the field of quantum matter physics. Here, we directly test the consistency of results from these…

Edoardo Cappelli, Willem O. Tromp, Siobhan Mckeown Walker, Anna Tamai, Marta Gibert Gutierrez, Felix Baumberger and Flavio Yair Bruno

APL Materials 8 5, 051102 (2020)

Irène Cucchi, A. Marrazzo, Edoardo Cappelli, Sara Ricco, F. Y. Bruno, Simone Lisi, M. Hoesch, T. K. Kim, C. Cacho, Céline Besnard, Enrico Giannini, N. Marzari, Marco Gibertini, Felix Baumberger and Anna Tamai

Physical Review Letters 124 106402 (2020)

Simone Lisi, Xiaobo Lu, Tjerk Benschop, Tobias A. de Jong, Petr Stepanov, Jose R. Duran, Florian Margot, Irène Cucchi, Edoardo Cappelli, Andrew Scott Hunter, Anna Tamai, Viktor Kandyba, Alessio Giampietri, Alexei Barinov, Johannes Jobst, Vincent Stalman, Maarten Leeuwenhoek, Kenji Watanabe, Takashi Taniguchi, Louk Rademaker, Sense Jan van der Molen, Milan P. Allan, Dmitri K. Efetov and Felix Baumberger

Nature physics 17 2, 189-193 (2020)

We combine different imaging techniques and angle-resolved photoemission with simultaneous real- and momentum-space resolution (nano-ARPES) to directly map the band dispersion in twisted bilayer graphene devices near charge neutrality. Our experiments reveal large areas with a homogeneous twist…

C.D. Dashwood, H. Miao, J.G. Vale, D. Ishikawa, D.A. Prishchenko, V.V. Mazurenko, V.G. Mazurenko, R.S. Perry, G. Cao, Alberto De La Torre, Felix Baumberger, A.Q.R. Baron, D.F. McMorrow and M.P.M. Dean

Physical Review. B, Condensed Matter 100 085131, 1-8 (2019)

The mixing of orbital and spin character in the wave functions of the 5d iridates has led to predictions of strong couplings among their lattice, electronic, and magnetic degrees of freedom. As well as realizing a novel spin-orbit assisted Mott-insulating ground state, the perovskite iridate…

Diogo C. Vaz, Paul Noël, Annika Johansson, Börge Göbel, Flavio Yair Bruno, Gyanendra Singh, Siobhan Mckeown Walker, Felix Trier, Luis M. Vicente-Arche, Anke Sander, Sergio Valencia, Pierre Bruneel, Manali Vivek, Marc Gabay, Nicolas Bergeal, Felix Baumberger, Hanako Okuno, Agnès Barthélémy, Albert Fert, Laurent Vila, Ingrid Mertig, Jean-Philippe Attané and Manuel Bibes

Nature Materials (2019)

While spintronics has traditionally relied on ferromagnetic metals as spin generators and detectors, spin–orbitronics exploits the efficient spin–charge interconversion enabled by spin–orbit coupling in non-magnetic systems. Although the Rashba pic- ture of split parabolic bands is often used …

Anna Tamai, M. Zingl, E. Rozbicki, Edoardo Cappelli, Sara Ricco, Alberto De La Torre, Siobhan Mckeown Walker, Flavio Yair Bruno, P.D.C. King, W. Meevasana, M. Shi, M. Radovic, N.C. Plumb, A.S. Gibbs, A.P. Mackenzie, Christophe Berthod, Hugo Strand, M. Kim, Antoine Georges and Felix Baumberger

Physical Review X 9 021048, 1-18 (2019)

We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals…

Flavio Yair Bruno, Siobhan Mckeown Walker, Sara Ricco, Alberto De La Torre, Zhiming Wang, Anna Tamai, Timur K. Kim, Moritz Hoesch, Mohammad S. Bahramy and Felix Baumberger

Advanced Electronic Materials 5 1800860, 1-7 (2019)

2D electron gases (2DEGs) in oxides show great potential for the discovery of new physical phenomena and at the same time hold promise for electronic applications. In this work, angle-resolved photoemission is used to determine the electronic structure of a 2DEG stabilized in the (111)-oriented…

Kai Wang, Nimrod Bachar, Jérémie Teyssier, Weiwei Luo, Willem Rischau, Gernot Scheerer, Alberto De La Torre, R. S. Perry, Felix Baumberger and Dirk Van Der Marel

Physical Review. B, Condensed Matter 98 045107, 1-12 (2018)

We studied the in-plane dynamic and static charge conductivity of electron doped Sr2IrO4 using optical spectroscopy and DC transport measurements. The optical conductivity indicates that the pristine material is an indirect semiconductor with a direct Mott gap of 0.55 eV. Upon substitution of 2% La …

Davide Pincini, S. Boseggia, R. Perry, M. J. Gutmann, Sara Ricco, L. S. I. Veiga, C. D. Dashwood, S. P. Collins, G. Nisbet, A. Bombardi, D. G. Porter, Felix Baumberger, A. T. Boothroyd and D. F. McMorrow

Physical Review. B, Condensed Matter 98 014429, 1-9 (2018)

The chemical and magnetic structures of the series of compounds Ca2−xLaxRuO4 [x = 0, 0.05(1), 0.07(1), 0.12(1)] have been investigated using neutron diffraction and resonant elastic x-ray scattering. Upon La doping, the low-temperature S-Pbca space group of the parent compound is retained in all…

Pan He, Siobhan Mckeown Walker, Steven S.-L. Zhang, Flavio Yair Bruno, M. S. Bahramy, Jong Min Lee, Rajagopalan Ramaswamy, Kaiming Cai, Olle Heinonen, Giovanni Vignale, Felix Baumberger and Hyunsoo Yang

Physical Review Letters 120 266802, 1-5 (2018)

We explore the second order bilinear magnetoelectric resistance (BMER) effect in the d-electron-based two-dimensional electron gas (2DEG) at the SrTiO3 (111) surface. We find evidence of a spin-split band structure with the archetypal spin-momentum locking of the Rashba effect for the in-plane…

Siobhan Mckeown Walker, Flavio Yair Bruno and Felix Baumberger

Spectroscopy of Complex Oxide Interfaces, 55-85 (2018)

Sara Ricco

Thèse (2018)

Ca2RuO4 is a multi-band Mott transition system with a ground state that is known to be sensitive to external perturbations, such as chemical substitution, pressure, strain and electric fields. In this work I utilize such sensitivity to determine its electronic structure evolution by angle-resolved…

Irène Cucchi, Ignacio Gutierrez Lezama, Edoardo Cappelli, Siobhan Mckeown Walker, Flavio Yair Bruno, Giulia Tenasini, Lin Wang, Nicolas Ubrig, Céline Barreteau, Enrico Giannini, Marco Gibertini, Anna Tamai, Alberto Morpurgo and Felix Baumberger

Nano Letters (2018)

Two-dimensional crystals of semi-metallic van der Waals materials hold much potential for the realization of novel phases, as exemplified by the recent discoveries of a polar metal in few-layer 1T′-WTe2 and of a quantum spin Hall state in monolayers of the same material. Understanding these…

Sara Ricco, M. Kim, Anna Tamai, Siobhan Mckeown Walker, Flavio Yair Bruno, Irène Cucchi, Edoardo Cappelli, Céline Besnard, T. K. Kim, P. Dudin, M. Hoesch, M. J. Gutmann, Antoine Georges, R. S. Perry and Felix Baumberger

Nature Communications 9 1, 4535 (2018)

Pressure plays a key role in the study of quantum materials. Its application in angle resolved photoemission (ARPES) studies, however, has so far been limited. Here, we report the evolution of the k-space electronic structure of bulk Ca2RuO4, lightly doped with Pr, under uniaxial strain. Using…

D. Pincini, J. G. Vale, C. Donnerer, Alberto De La Torre, E. C. Hunter, R. Perry, M. Moretti Sala, Felix Baumberger and D. F. McMorrow

Physical Review. B, Condensed Matter 96 7 (2017)

The collective magnetic excitations in the spin-orbit Mott insulator (Sr1−xLax)2IrO4 (x=0,0.01,0.04,0.1) were investigated by means of resonant inelastic x-ray scattering. We report significant magnon energy gaps at both the crystallographic and antiferromagnetic zone centers at all doping…

Z. Wang, Z. Zhong, Siobhan Mckeown Walker, Z. Ristic, J.-Z. Ma, Flavio Yair Bruno, Sara Ricco, G. Sangiovanni, G. Eres, N. C. Plumb, L. Patthey, M. Shi, J. Mesot, Felix Baumberger and M. Radovic

Nano Letters 17 4, 2561-2567 (2017)

Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL…

I. Battisti, V. Fedoseev, K. M. Bastiaans, Alberto De La Torre, R. S. Perry, Felix Baumberger and M. P. Allan

Physical Review. B, Condensed Matter 95 23 (2017)

The effective Mott gap measured by scanning tunneling microscopy (STM) in the lightly doped Mott insulator (Sr1−xLax)2IrO4 differs greatly from values reported by photoemission and optical experiments. Here we show that this is a consequence of the poor electronic screening of the tip-induced…

Flavio Yair Bruno, Marta Gibert Gutierrez, Siobhan Mckeown Walker, Oleg Peil, Alberto De La Torre, Sara Ricco, Zhe Wang, Sara Catalano, Anna Tamai, F. Bisti, V.N. Strocov, Jean-Marc Triscone and Felix Baumberger

APL Materials 5 1, 016101 (2017)

M. Hoesch, T. K. Kim, P. Dudin, H. Wang, S. Scott, P. Harris, S. Patel, M. Matthews, D. Hawkins, S. G. Alcock, T. Richter, J. J. Mudd, M. Basham, L. Pratt, P. Leicester, E. C. Longhi, Anna Tamai and Felix Baumberger

Review of Scientific Instruments 88 1, 013106 (2017)

A synchrotron radiation beamline in the photon energy range of 18-240 eV and an electron spectroscopy end station have been constructed at the 3 GeV Diamond Light Source storage ring. The instrument features a variable polarisation undulator, a high resolution monochromator, a re-focussing system…

Siobhan Mckeown Walker

Thèse (2016)

In this thesis I have investigated the electronic structure of two-dimensional electron liquids (2DEL) induced at different surfaces of the transition metal oxide band insulators SrTiO3, KTaO3 and anatase TiO2 by angle-resolved photoemission spectroscopy (ARPES). I present high-resolution ARPES…

I. Battisti, K. M. Bastiaans, V. Fedoseev, Alberto De La Torre, N. Iliopoulos, Anna Tamai, E. C. Hunter, R. S. Perry, J. Zaanen, Felix Baumberger and M. P. Allan

Nature physics 13 1, 21-25 (2016)

Z. Wang, Siobhan Mckeown Walker, Anna Tamai, Y. Wang, Z. Ristic, Flavio Yair Bruno, Alberto De La Torre, Sara Ricco, N. C. Plumb, M. Shi, P. Hlawenka, J. Sánchez-Barriga, A. Varykhalov, T. K. Kim, M. Hoesch, P. D. C. King, W. Meevasana, U. Diebold, J. Mesot, B. Moritz, T. P. Devereaux, M. Radovic and Felix Baumberger

Nature materials 15 8, 835-839 (2016)

Anna Tamai, Q. S. Wu, Irène Cucchi, Flavio Yair Bruno, Sara Ricco, T. K. Kim, M. Hoesch, Céline Barreteau, Enrico Giannini, Céline Besnard, A. A. Soluyanov and Felix Baumberger

Physical review. X 6, 031021 (2016)

Flavio Yair Bruno, Anna Tamai, Q. S. Wu, Irène Cucchi, Céline Barreteau, Alberto De La Torre, Siobhan Mckeown Walker, Sara Ricco, Z. Wang, T. K. Kim, M. Hoesch, M. Shi, N. C. Plumb, Enrico Giannini, A. A. Soluyanov and Felix Baumberger

Physical review. B, Condensed matter and materials physics 94, 121112(R) (2016)

Siobhan Mckeown Walker, Sara Ricco, Flavio Yair Bruno, Alberto De La Torre, Anna Tamai, E. Golias, A. Varykhalov, D. Marchenko, M. Hoesch, M. S. Bahramy, P. D. C. King, J. Sánchez-Barriga and Felix Baumberger

Physical review. B, Condensed matter and materials physics 93, 245143 (2016)

Alberto De La Torre

Thèse (2015)

This thesis reports the doping evolution of the electronic structure of the single and bilayer idridates Sr2IrO4 and Sr3Ir2O7 from angle resolved photoemission (ARPES) experiments.

Alberto De La Torre, Siobhan Mckeown Walker, Flavio Yair Bruno, Sara Ricco, Z. Wang, Ignacio Gutierrez Lezama, Gernot Scheerer, Gaétan Giriat, Didier Jaccard, Christophe Berthod, T. K. Kim, M. Hoesch, E. C. Hunter, R. S. Perry, Anna Tamai and Felix Baumberger

Physical review letters 115, 176402 (2015)

We report angle resolved photoemission experiments on the electron doped Heisenberg antiferromagnet Sr1−xLax2IrO4. For a doping level of x 1⁄4 0.05, we find an unusual metallic state with coherent nodal excitations and an antinodal pseudogap bearing strong similarities with underdoped cuprates. …

Siobhan Mckeown Walker, Flavio Yair Bruno, Zhiming Wang, Alberto De La Torre, Sara Ricco, Anna Tamai, Timur K. Kim, Moritz Hoesch, Ming Shi, Mohammad Saeed Bahramy, Phil D. C. King and Felix Baumberger

Advanced materials 27 26, 3894-3899 (2015)

The origin of the 2D electron gas (2DEG)stabilized at the bare surface of SrTiO3 (001) is investigated. Using high-resolution angle-resolved photoemission and core-level spectroscopy, it is shown conclusively that this 2DEG arises from light-induced oxygen vacancies. The dominant mechanism driving…

T. Eknapakul, P. D. C. King, M. Asakawa, P. Buaphet, R.-H. He, S.-K. Mo, H. Takagi, K. M. Shen, Felix Baumberger, T. Sasagawa, S. Jungthawan and W. Meevasana

Nano letters 14 3, 1312-1316 (2014)

Several transition-metal dichalcogenides exhibit a striking crossover from indirect to direct band gap semiconductors as they are thinned down to a single monolayer. Here, we demonstrate how an electronic structure characteristic of the isolated monolayer can be created at the surface of a bulk…

Siobhan Mckeown Walker, Alberto De La Torre, Flavio Yair Bruno, Anna Tamai, T. K. Kim, M. Hoesch, M. Shi, M. S. Bahramy, P. D. C. King and Felix Baumberger

Physical review letters 113 17, 177601 (2014)

We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a sixfold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of…

P. D. C. King, Siobhan Mckeown Walker, Anna Tamai, Alberto De La Torre, T. Eknapakul, P. Buaphet, S.-K. Mo, W. Meevasana, M. S. Bahramy and Felix Baumberger

Nature communications 5 3414, 5 (2014)

Two-dimensional electron gases (2DEGs) in SrTiO3 have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here we demonstrate that angle-resolved photoemission…

Alberto De La Torre, E. C. Hunter, A. Subedi, Siobhan Mckeown Walker, Anna Tamai, T. K. Kim, M. Hoesch, R. S. Perry, Antoine Georges and Felix Baumberger

Physical review letters 113, 256402 (2014)

We characterize the electron doping evolution of (Sr1−xLax)3Ir2O7 by means of angle-resolved photoemission. Concomitant with the metal insulator transition around x≈0.05 we find the emergence of coherent quasiparticle states forming a closed small Fermi surface of volume 3x/2, where x is the…

Anna Tamai, W. Meevasana, P. D. C. King, C. W. Nicholson, Alberto De La Torre, E. Rozbicki and Felix Baumberger

Physical review. B, Condensed matter and materials physics 87 07, 075113 (2013)

We present angle-resolved photoemission data from Cu(111). Using a focused 6 eV continuous-wave laser for photoexcitation, we achieve a high effective momentum resolution, enabling detection of the Rashba spin splitting in the Shockley surface state on Cu(111). The magnitude of the spin splitting…

M. P. Allan, Anna Tamai, E. Rozbicki, M. H. Fischer, J. Voss, P. D. C. King, W. Meevasana, S. Thirupathaiah, E. Rienks, J. Fink, D. A. Tennant, R. S. Perry, J. F. Mercure, M. A. Wang, Jinho Lee, C. J. Fennie, E.-A. Kim, M. J. Lawler, K. M. Shen, A. P. Mackenzie, Z.-X. Shen and Felix Baumberger

New journal of physics 15 6, 063029 (2013)

The phase diagram of Sr3Ru2O7 shows hallmarks of strong electron correlations despite the modest Coulomb interaction in the Ru 4d shell. We use angle-resolved photoelectron spectroscopy measurements to provide microscopic insight into the formation of the strongly renormalized heavy d-electron…

P. D. C. King, T. Takayama, Anna Tamai, E. Rozbicki, Siobhan Mckeown Walker, M. Shi, L. Patthey, R. G. Moore, D. Lu, K. M. Shen, H. Takagi and Felix Baumberger

Physical review. B, Condensed matter and materials physics 87 24 (2013)

We investigate the bilayer Ruddlesden-Popper iridate Sr3Ir2O7 by temperature-dependent angle-resolved photoemission. At low temperatures, we find a fully gapped correlated insulator, characterized by a small charge gap and narrow bandwidths. The low-energy spectral features show a pronounced…

M.S. Bahramy, P.D.C King, Alberto De La Torre, J. Chang, M. Shi, L. Patthey, G. Balakrishnan, Ph. Hofmann, R. Arita, N. Nagaosa and Felix Baumberger

Nature communications 3 1159 (2012)

Bismuth-chalchogenides are model examples of three-dimensional topological insulators. Their ideal bulk-truncated surface hosts a single spin-helical surface state, which is the simplest possible surface electronic structure allowed by their non-trivial Z2 topology. However, real surfaces of such…

P. D. C. King, R. H. He, T. Eknapakul, P. Buaphet, S.-K. Mo, Y. Kaneko, S. Harashima, Y. Hikita, M. S. Bahramy, C. Bell, Z. Hussain, Y. Tokura, Z.-X. Shen, H. Y. Hwang, Felix Baumberger and W. Meevasana

Physical review letters 108 11, 117602 (2012)

We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of…

D. O. Scanlon, P. D. C. King, R. P. Singh, Alberto De La Torre, Siobhan Mckeown Walker, G. Balakrishnan, Felix Baumberger and C. R. A. Catlow

Advanced materials 24 16, 2154-2158 (2012)

Intrinsic topological insulators are realized by alloying Bi2Te3 with Bi2Se3. Angle-resolved photoemission and bulk transport measurements reveal that the Fermi level is readily tuned into the bulk bandgap. First-principles calculations of the native defect landscape highlight the key role of…

P. D. C. King, R. C. Hatch, M. Bianchi, R. Ovsyannikov, C. Lupulescu, G. Landolt, B. Slomski, J. H. Dil, D. Guan, J. L. Mi, E. D. L. Rienks, J. Fink, A. Lindblad, S. Svensson, S. Bao, G. Balakrishnan, B. B. Iversen, J. Osterwalder, W. Eberhardt, Felix Baumberger and Ph. Hofmann

Physical review letters 107 09, 096802 (2011)

We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi2Se3 from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger…

P. D. C. King, J. A. Rosen, W. Meevasana, Anna Tamai, E. Rozbicki, R. Comin, G. Levy, D. Fournier, Y. Yoshida, H. Eisaki, K. M. Shen, N. J. C. Ingle, A. Damascelli and Felix Baumberger

Physical review letters 106 12, 127005 (2011)

We observe apparent hole pockets in the Fermi surfaces of single-layer Bi-based cuprate superconductors from angle-resolved photoemission. From detailed low-energy electron diffraction measurements and an analysis of the angle-resolved photoemission polarization dependence, we show that these…

W. Meevasana, P. D. C. King, R. H. He, S-K. Mo, M. Hashimoto, Anna Tamai, P. Songsiriritthigul, Felix Baumberger and Z-X. Shen

Nature materials 10 2, 114-118 (2011)

Many-body interactions in transition-metal oxides give rise to a wide range of functional properties, such as high-temperature superconductivity1, colossal magnetoresistance2 or multiferroicity 3. The seminal recent discovery of a two-dimensional electron gas (2DEG) at the interface of the…

W Meevasana, X J Zhou, B Moritz, C-C Chen, R H He, S-I Fujimori, D H Lu, S-K Mo, R G Moore, Felix Baumberger, T P Devereaux, Dirk Van Der Marel, N Nagaosa, J Zaanen and Z-X Shen

New journal of physics 12 2, 023004 (2010)

Anna Tamai, Felix Baumberger, M. Hengsberger, J. Lobo-Checa, M. Muntwiler, M. Corso, C. Cirelli, L. Patthey, Z.-X. Shen, T. Greber and J. Osterwalder

Physical review. B, Condensed matter and materials physics 81 04, 045423 (2010)

The low-energy single-particle excitations of highly ordered C60 chains adsorbed on a vicinal copper substrate are investigated by angle-resolved photoemission spectroscopy. The interface state previously identified on C60/Cu(111) shows a one-dimensional dispersion on Cu(553). In contrast, no…

Anna Tamai, A. Y. Ganin, E. Rozbicki, J. Bacsa, W. Meevasana, P. D. C. King, M. Caffio, R. Schaub, S. Margadonna, K. Prassides, M. J. Rosseinsky and Felix Baumberger

Physical review letters 104 09, 097002 (2010)

We investigate the normal state of the “11” iron-based superconductor FeSe0.42Te0.58 by angle-resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between…

Jinho Lee, M. P. Allan, M. A. Wang, J. Farrell, S. A. Grigera, Felix Baumberger, J. C. Davis and A. P. Mackenzie

Nature physics 5 11, 800-804 (2009)

The intriguing idea that strongly interacting electrons can generate spatially inhomogeneous electronic liquid-crystalline phases is over a decade old1, 2, 3, 4, 5, but these systems still represent an unexplored frontier of condensed-matter physics. One reason is that visualization of the…

Michael Straub

Thèse, 113 (2026)

Recent advances in microfocused angle-resolved photoemission (micro-ARPES) enable the investigation of momentum-resolved electronic structure on micron length scales. This thesis uses these capabilities to study three different quantum materials: bulk 1T-TaSe₂, strained…

Salony Mandloi

Thèse (2026)

Two-dimensional Janus transition metal dichalcogenides are a unique class of materials with broken inversion symmetry and an intrinsic electric field across the layer. In this thesis, we investigate RhSeCl, a newly synthesized Janus semiconductor with exceptionally low chalcogen mixing. Using…

Julia Issing

Thèse (2024)

Thinning a bulk material down to a few atomic layers or even to a monolayer influences its physical properties considerably. Such two-dimensional materials can also be used to engineer new correlated phases by stacking them on top of each other. In the present thesis, I present my work on twisted…

Florian Margot

Thèse, 136 (2023)

2D semiconducting materials represent an interesting opportunity for the desired scaling of electronic devices. Black phosphorus (PB) is a promising candidate because of its direct gap in the range of telecommunications wavelengths and a comparatively high room-temperature mobility that compares…

Andrew Scott Hunter

Thèse (2023)

In its normal state, Sr₂RuO₄ is a prototypical Fermi liquid below ∼ 25 K. At ∼ 1.5 K it undergoes a superconducting transition, but it has long remained challenging to determine the symmetry or order parameter of the superconducting state. Recent experiments have shown…

Edoardo Cappelli

Thèse (2021)

In this thesis, I present my research work on epitaxial thin films of LaNiO3 and SrMoO3, investigated by angle-resolved photoemission spectroscopy (ARPES), which yields a direct measurement of the interacting electronic structure. Thin films of the correlated transition-metal oxide LaNiO3 undergo a …

Irène Cucchi

Thèse (2020)

Van der Waals materials can be exfoliated down to atomically thin crystals, offering potential to explore physics in lower dimensionality. In this thesis, I investigated their topological electronic structure with ARPES. I studied mono-, bi- and few-layer Td-WTe2. The small size of exfoliated…

Sara Ricco

Thèse (2018)

Ca2RuO4 is a multi-band Mott transition system with a ground state that is known to be sensitive to external perturbations, such as chemical substitution, pressure, strain and electric fields. In this work I utilize such sensitivity to determine its electronic structure evolution by angle-resolved…

Siobhan Mckeown Walker

Thèse (2016)

In this thesis I have investigated the electronic structure of two-dimensional electron liquids (2DEL) induced at different surfaces of the transition metal oxide band insulators SrTiO3, KTaO3 and anatase TiO2 by angle-resolved photoemission spectroscopy (ARPES). I present high-resolution ARPES…

Alberto De La Torre

Thèse (2015)

This thesis reports the doping evolution of the electronic structure of the single and bilayer idridates Sr2IrO4 and Sr3Ir2O7 from angle resolved photoemission (ARPES) experiments.