Showing 1–8 of 8 results for author: Jovic, V

Moiré-resonant surface state in ultrathin RuO$_2$

Authors: Philipp Keßler, Andreas Feuerpfeil, Armando Consiglio, Hendrik Hohmann, Ronny Thomale, Jonas Erhardt, Bing Liu, Vedran Jovic, Ralph Claessen, Patrick Härtl, Matteo Dürrnagel, Simon Moser

Abstract: RuO$_2$ has emerged as a prototypical candidate for altermagnetism. In the face of daunting evidence for magnetic order in the bulk, the focus naturally shifted to surfaces and ultrathin films, where Coulomb interactions are dimensionally quenched and electron correlations strongly enhanced. Here, we examine atomically ordered, ultrathin RuO$_2$(110) grown on Ru(0001) using a combination of scanni… ▽ More RuO$_2$ has emerged as a prototypical candidate for altermagnetism. In the face of daunting evidence for magnetic order in the bulk, the focus naturally shifted to surfaces and ultrathin films, where Coulomb interactions are dimensionally quenched and electron correlations strongly enhanced. Here, we examine atomically ordered, ultrathin RuO$_2$(110) grown on Ru(0001) using a combination of scanning tunneling microscopy (STM), density functional theory, and density matrix renormalization group methods. We observe a nonmagnetic charge order that is imprinted by the incommensurate moiré stacking with the substrate and enhanced by the electronic Fermi surface scattering within the flat-band surface state. We further identify a nonmagnetic, metastable $c(2 \times 2)$ surface reconstruction that arises from surface phonon softening and can be toggled reversibly via STM tip manipulation. Spin-polarized STM measurements, however, reveal no evidence of magnetic order on the RuO$_2$(110) surface. Our findings of a nonmagnetic charge-modulation position ultrathin RuO$_2$(110) as an intriguing platform for exploring moiré-assisted electronic orders. △ Less

Submitted 19 July, 2026; v1 submitted 7 July, 2025; originally announced July 2025.

Journal ref: Phys. Rev. Research 8, 033058 (2026)

Epitaxial RuO$_2$ and IrO$_2$ films by pulsed laser deposition on TiO$_2$(110)

Authors: Philipp Keßler, Tim Waldsauer, Vedran Jovic, Martin Kamp, Matthias Schmitt, Michael Sing, Ralph Claessen, Simon Moser

Abstract: We present a systematic growth study of epitaxial RuO$_2$(110) and IrO$_2$(110) on TiO$_2$(110) substrates by pulsed laser deposition. We describe the main challenges encountered in the growth process, such as a deteriorating material flux due to laser induced target metallization or the delicate balance of under- vs over-oxidation of the 'stubborn' Ru and Ir metals. We identify growth temperature… ▽ More We present a systematic growth study of epitaxial RuO$_2$(110) and IrO$_2$(110) on TiO$_2$(110) substrates by pulsed laser deposition. We describe the main challenges encountered in the growth process, such as a deteriorating material flux due to laser induced target metallization or the delicate balance of under- vs over-oxidation of the 'stubborn' Ru and Ir metals. We identify growth temperatures and oxygen partial pressures of 700 K, $1\times 10^{-3}$ mbar for RuO$_2$ and 770 K, $5\times 10^{-4}$ mbar for IrO$_2$ to optimally balance between metal oxidation and particle mobility during nucleation. In contrast to IrO$_2$, RuO$_2$ exhibits layer-by-layer growth up to 5 unit cells if grown at high deposition rates. At low deposition rates, the large lattice mismatch between film and substrate fosters initial 3D island growth and cluster formation. In analogy to reports for RuO$_2$ based on physical vapor deposition, we find these islands to eventually merge and growth to continue in a step flow mode, resulting in highly crystalline, flat, stoichiometric films of RuO$_2$(110) (up to 30 nm thickness) and IrO$_2$(110) (up to 13 nm thickness) with well defined line defects. △ Less

Submitted 21 May, 2024; originally announced May 2024.

Comments: 15 pages, 12 figures

Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

Authors: Teresa Tschirner, Philipp Keßler, Ruben Dario Gonzalez Betancourt, Tommy Kotte, Dominik Kriegner, Bernd Buechner, Joseph Dufouleur, Martin Kamp, Vedran Jovic, Libor Smejkal, Jairo Sinova, Ralph Claessen, Tomas Jungwirth, Simon Moser, Helena Reichlova, Louis Veyrat

Abstract: Observations of the anomalous Hall effect in RuO$_2$ and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in Ru… ▽ More Observations of the anomalous Hall effect in RuO$_2$ and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO$_2$ is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis towards the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO$_2$ thin-film samples whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field $H_{\rm c} \simeq$ 55 T that was inaccessible in earlier studies, but is consistent with the expected Néel-vector reorientation field. △ Less

Submitted 1 September, 2023; originally announced September 2023.

Comments: 4 figures

Journal ref: APL Mater. 11, 101103 (2023)

The Dirac nodal line network in non-symmorphic rutile semimetal RuO$_2$

Authors: Vedran Jovic, Roland J. Koch, Swarup K. Panda, Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Ronny Thomale, Kevin E. Smith, Silke Biermann, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Domenico Di Sante, Simon Moser

Abstract: We employ angle resolved photoemission spectroscopy (ARPES) to investigate the Fermi surface of RuO$_2$. We find a network of two Dirac nodal lines (DNL) as previously predicted in theory, where the valence- and conduction bands touch along continuous lines in momentum space. In addition, we find evidence for a third DNL close to the Fermi level which appears robust despite the presence of signifi… ▽ More We employ angle resolved photoemission spectroscopy (ARPES) to investigate the Fermi surface of RuO$_2$. We find a network of two Dirac nodal lines (DNL) as previously predicted in theory, where the valence- and conduction bands touch along continuous lines in momentum space. In addition, we find evidence for a third DNL close to the Fermi level which appears robust despite the presence of significant spin orbit coupling. We demonstrate that the third DNL gives rise to a topologically trivial flat-band surface state (FBSS) at the (110) surface. This FBSS can be tuned by surface doping and presents an interesting playground for the study of surface chemistry and exotic correlation phenomena. △ Less

Submitted 6 August, 2019; originally announced August 2019.

Comments: 12 pages, 9 figures

Nano-engineering of electron correlation in oxide superlattices

Authors: J. Laverock, M. Gu, V. Jovic, J. W. Lu, S. A. Wolf, R. M. Qiao, W. Yang, K. E. Smith

Abstract: Oxide heterostructures and superlattices have attracted a great deal of attention in recent years owing to the rich exotic properties encountered at their interfaces. We focus on the potential of tunable correlated oxides by investigating the spectral function of the prototypical correlated metal SrVO3, using soft x-ray absorption spectroscopy (XAS) and resonant inelastic soft x-ray scattering (RI… ▽ More Oxide heterostructures and superlattices have attracted a great deal of attention in recent years owing to the rich exotic properties encountered at their interfaces. We focus on the potential of tunable correlated oxides by investigating the spectral function of the prototypical correlated metal SrVO3, using soft x-ray absorption spectroscopy (XAS) and resonant inelastic soft x-ray scattering (RIXS) to access both unoccupied and occupied electronic states, respectively. We demonstrate a remarkable level of tunability in the spectral function of SrVO3 by varying its thickness within the SrVO3/SrTiO3 superlattice, showing that the effects of electron correlation can be tuned from dominating the energy spectrum in a strongly correlated Mott-Hubbard insulator, towards a correlated metal. We show that the effects of dimensionality on the correlated properties of SrVO3 are augmented by interlayer coupling, yielding a highly flexible correlated oxide that may be readily married with other oxide systems. △ Less

Submitted 14 March, 2019; originally announced March 2019.

Journal ref: Nano Futures 1, 031001 (2017)

Observation of weakened V-V dimers in the monoclinic metallic phase of strained VO2

Authors: J. Laverock, V. Jovic, A. A. Zakharov, Y. R. Niu, S. Kittiwatanakul, B. Westhenry, J. W. Lu, S. A. Wolf, K. E. Smith

Abstract: Emergent order at mesoscopic length scales in condensed matter can provide fundamental insight into the underlying competing interactions and their relationship with the order parameter. Using spectromicroscopy, we show that mesoscopic stripe order near the metal-insulator transition (MIT) of strained VO2 represent periodic modulations in both crystal symmetry and V-V dimerization. Above the MIT,… ▽ More Emergent order at mesoscopic length scales in condensed matter can provide fundamental insight into the underlying competing interactions and their relationship with the order parameter. Using spectromicroscopy, we show that mesoscopic stripe order near the metal-insulator transition (MIT) of strained VO2 represent periodic modulations in both crystal symmetry and V-V dimerization. Above the MIT, we unexpectedly find the long range order of V-V dimer strength and crystal symmetry become dissociated beyond ~ 200 nm, whereas the conductivity transition proceeds homogeneously in a narrow temperature range. △ Less

Submitted 13 March, 2019; originally announced March 2019.

Journal ref: Phys. Rev. Lett. 121, 256403 (2018)

Observation of surface states on heavily indium doped SnTe(111), a superconducting topological crystalline insulator

Authors: C. M. Polley, V. Jovic, T. -Y. Su, M. Saghir, D. Newby Jr., B. Kowalski, R. Jakiela, A. Barcz, M. Guziewicz, T. Balasubramanian, G. Balakrishnan, J. Laverock, K. E. Smith

Abstract: The topological crystalline insulator tin telluride is known to host superconductivity when doped with indium (Sn$_{1-x}$In$_{x}$Te), and for low indium contents ($x=0.04$) it is known that the topological surface states are preserved. Here we present the growth, characterization and angle resolved photoemission spectroscopy analysis of samples with much heavier In doping (up to $x\approx0.4$), a… ▽ More The topological crystalline insulator tin telluride is known to host superconductivity when doped with indium (Sn$_{1-x}$In$_{x}$Te), and for low indium contents ($x=0.04$) it is known that the topological surface states are preserved. Here we present the growth, characterization and angle resolved photoemission spectroscopy analysis of samples with much heavier In doping (up to $x\approx0.4$), a regime where the superconducting temperature is increased nearly fourfold. We demonstrate that despite strong p-type doping, Dirac-like surface states persist. △ Less

Submitted 18 February, 2016; v1 submitted 16 August, 2015; originally announced August 2015.

Journal ref: Phys. Rev. B 93, 075132 (2016)

Proceedings of the 35th Annual Australian/New Zealand Condensed Matter and Materials Meeting

Authors: K. Radhanpura, S. Hargreaves, R. A. Lewis, H. Krüger, E. Rey, P. -Z. Si, T. Söhnel, V. Jovic, J. B. Metson, G. I. N. Waterhouse, A. A. Abiona, W. J. Kemp, A. P. Byrne, M. C. Ridgeway, H. Timmers, J. D. Cashion, W. P. Gates, T. L. Greaves, O. Dorjkhaidav, E. Constable, L. G. Gladkis, J. M. Scarvell, P. N. Smith, C. J. Hamer, O. Rojas , et al. (20 additional authors not shown)

Abstract: The 35th Australian/New Zealand Annual Condensed Matter and Materials Meeting was held at the Charles Sturt University campus in Wagga Wagga, NSW, Australia from the 1st to the 4th of February 2011. The conference was attended by 92 delegates from a range of universities across Australia, New Zealand and further afield. There were a total of 9 invited and 21 contributed talks during the three da… ▽ More The 35th Australian/New Zealand Annual Condensed Matter and Materials Meeting was held at the Charles Sturt University campus in Wagga Wagga, NSW, Australia from the 1st to the 4th of February 2011. The conference was attended by 92 delegates from a range of universities across Australia, New Zealand and further afield. There were a total of 9 invited and 21 contributed talks during the three days of scientific sessions, as well as 2 poster sessions with a total of 49 poster presentations. All presenters were invited to submit a manuscript for publication in the conference proceedings. The length limits where six pages for invited papers and four pages for contributed papers. Each manuscript was reviewed by two anonymous referees and 18 papers were accepted for publication. The accepted manuscripts are also available at the online publication section of the Australian Institute of Physics national web site (http://www.aip.org.au/). △ Less

Submitted 18 July, 2011; originally announced July 2011.

Comments: A.P. Micolich (Editor), ISBN 978-0-646-55969-8 (2011). 18 papers from 35th Australian/New Zealand Annual Condensed Matter and Materials Meeting, 85 pages