Diego A. Zocco
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Research Interests
Diego A. Zocco has a total of 186 co-authors. Here are the top co-authors by number of shared publications:
- James Jeffrey Hamlin
Department of Physics, University of Florida, Gainesville, USA
15 shared publications M. B. Maple
Department of Physics University of California San Diego La Jolla 92093 California USA
7 shared publications- Silke Paschen
Institute of Solid State Physics, TU Wien, Vienna, Austria
6 shared publications - Andrey Prokofiev
Institute of Solid State Physics, Vienna University of Technology, A-1040 Wien, Austria
5 shared publications I. R. Fisher
Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, California 94305, USA
5 shared publicationsM B Maple
5 shared publications
Latest Publications
- Open Access
- 14 January 2026
- Published by Springer Nature in Nature Physics
- Vol. 22 (2) , 218-224
Emergent topological semimetal from quantum criticality
The electronic topology of a material is generally described by its Bloch states and the associated band structure, and can be altered by electron–electron interactions. In metallic systems, the interactions are usually treated through the concept of quasiparticles. Here we investigate what happens if no well-defined quasiparticles are present and show that a topological semimetal phase can emerge from the material’s quantum critical state. Using the non-centrosymmetric heavy-fermion compound CeRu 4 Sn 6 , which is intrinsically quantum critical, we show that the topological phase exhibits a dome structure as a function of the magnetic field and pressure. To understand these results, we study a Weyl–Kondo semimetal model at a Kondo destruction quantum critical point. Indeed, it exhibits features in the spectral function that can define topological crossings beyond the quasiparticle picture. Our results outline the importance of the interplay of quantum critical fluctuations and symmetry to search for other emergent topological phases.
- 14 January 2026
- Published by Springer Nature in Nature Physics
- Vol. 22 (2) , 218-224
Open AccessEmergent topological semimetal from quantum criticality
The electronic topology of a material is generally described by its Bloch states and the associated band structure, and can be altered by electron–electron interactions. In metallic systems, the interactions are usually treated through the concept of quasiparticles. Here we investigate what happens if no well-defined quasiparticles are present and show that a topological semimetal phase can emerge from the material’s quantum critical state. Using the non-centrosymmetric heavy-fermion compound CeRu 4 Sn 6 , which is intrinsically quantum critical, we show that the topological phase exhibits a dome structure as a function of the magnetic field and pressure. To understand these results, we study a Weyl–Kondo semimetal model at a Kondo destruction quantum critical point. Indeed, it exhibits features in the spectral function that can define topological crossings beyond the quasiparticle picture. Our results outline the importance of the interplay of quantum critical fluctuations and symmetry to search for other emergent topological phases.
- Open Access
- 4 June 2024
- Published by American Physical Society (APS) in Physical Review Research
- Vol. 6 (2) , 023242
– A large hybridization-gap variant ofThe family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, . It is an isoelectronic analog of the prototypical Kondo insulator and of the recently discovered Weyl-Kondo semimetal . In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65–70 meV, about eight times larger than that in and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in . We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence , but instead with increasing partial electronic density of states of the orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials.- 4 June 2024
- Published by American Physical Society (APS) in Physical Review Research
- Vol. 6 (2) , 023242
Open Access– A large hybridization-gap variant ofThe family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, . It is an isoelectronic analog of the prototypical Kondo insulator and of the recently discovered Weyl-Kondo semimetal . In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65–70 meV, about eight times larger than that in and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in . We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence , but instead with increasing partial electronic density of states of the orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials. - Open Access
- 31 October 2022
- Published by Springer Nature in Nature Communications
- Vol. 13 (1) , 1
Author Correction: Control of electronic topology in a strongly correlated electron system
- 31 October 2022
- Published by Springer Nature in Nature Communications
- Vol. 13 (1) , 1
Open AccessAuthor Correction: Control of electronic topology in a strongly correlated electron system
- Open Access
- 29 September 2022
- Published by Springer Nature in Nature Communications
- Vol. 13 (1) , 1-7
Control of electronic topology in a strongly correlated electron system
It is becoming increasingly clear that breakthrough in quantum applications necessitates materials innovation. In high demand are conductors with robust topological states that can be manipulated at will. This is what we demonstrate in the present work. We discover that the pronounced topological response of a strongly correlated “Weyl-Kondo” semimetal can be genuinely manipulated—and ultimately fully suppressed—by magnetic fields. We understand this behavior as a Zeeman-driven motion of Weyl nodes in momentum space, up to the point where the nodes meet and annihilate in a topological quantum phase transition. The topologically trivial but correlated background remains unaffected across this transition, as is shown by our investigations up to much larger fields. Our work lays the ground for systematic explorations of electronic topology, and boosts the prospect for topological quantum devices.
- 29 September 2022
- Published by Springer Nature in Nature Communications
- Vol. 13 (1) , 1-7
Open AccessControl of electronic topology in a strongly correlated electron system
It is becoming increasingly clear that breakthrough in quantum applications necessitates materials innovation. In high demand are conductors with robust topological states that can be manipulated at will. This is what we demonstrate in the present work. We discover that the pronounced topological response of a strongly correlated “Weyl-Kondo” semimetal can be genuinely manipulated—and ultimately fully suppressed—by magnetic fields. We understand this behavior as a Zeeman-driven motion of Weyl nodes in momentum space, up to the point where the nodes meet and annihilate in a topological quantum phase transition. The topologically trivial but correlated background remains unaffected across this transition, as is shown by our investigations up to much larger fields. Our work lays the ground for systematic explorations of electronic topology, and boosts the prospect for topological quantum devices.
- Open Access
- 28 July 2022
- Published by Elsevier in Journal of Crystal Growth
- Vol. 595
A Knudsen cell approach for the molecular beam epitaxy of the heavy fermion compound YbRhSi- 28 July 2022
- Published by Elsevier in Journal of Crystal Growth
- Vol. 595
Open AccessA Knudsen cell approach for the molecular beam epitaxy of the heavy fermion compound YbRhSi - Open Access
- 15 April 2019
- Published by American Physical Society (APS) in Physical Review B
- Vol. 99 (13) , 134511
Electron-phonon coupling and superconductivity-induced distortion of the phonon lineshape inPhonon measurements in the -type superconductors were complicated in the past because of the unavailability of large single crystals for inelastic neutron scattering, e.g., in the case of , or unfavorable neutron scattering properties in the case of . Hence, only few studies of the lattice dynamical properties with momentum resolved methods were published, in particular below the superconducting transition temperature . Here, we overcome these problems by employing inelastic x-ray scattering and report a combined experimental and theoretical investigation of lattice dynamics in with the focus on the temperature-dependent properties of low-energy acoustic phonon modes in several high-symmetry directions. We paid particular attention to the evolution of the soft phonon mode of the structural phase transition observed in our sample at , i.e., just above the measured superconducting phase transition at . Theoretically, we predict lattice dynamics including electron-phonon coupling based on density-functional-perturbation theory and discuss the relevance of the soft phonon mode with regard to the value of . Furthermore, we explain superconductivity-induced anomalies in the lineshape of several acoustic phonon modes using a model proposed by Allen et al, [ Phys. Rev. B 56, 5552 (1997)].- 15 April 2019
- Published by American Physical Society (APS) in Physical Review B
- Vol. 99 (13) , 134511
Open AccessElectron-phonon coupling and superconductivity-induced distortion of the phonon lineshape inPhonon measurements in the -type superconductors were complicated in the past because of the unavailability of large single crystals for inelastic neutron scattering, e.g., in the case of , or unfavorable neutron scattering properties in the case of . Hence, only few studies of the lattice dynamical properties with momentum resolved methods were published, in particular below the superconducting transition temperature . Here, we overcome these problems by employing inelastic x-ray scattering and report a combined experimental and theoretical investigation of lattice dynamics in with the focus on the temperature-dependent properties of low-energy acoustic phonon modes in several high-symmetry directions. We paid particular attention to the evolution of the soft phonon mode of the structural phase transition observed in our sample at , i.e., just above the measured superconducting phase transition at . Theoretically, we predict lattice dynamics including electron-phonon coupling based on density-functional-perturbation theory and discuss the relevance of the soft phonon mode with regard to the value of . Furthermore, we explain superconductivity-induced anomalies in the lineshape of several acoustic phonon modes using a model proposed by Allen et al, [ Phys. Rev. B 56, 5552 (1997)]. - Open Access
- 12 September 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 98 (9) , 094304
Competing soft phonon modes at the charge-density-wave transitions inThe family of rare-earth () tritellurides features charge-density-wave (CDW) order related to strongly momentum-dependent electron-phonon coupling. Similar to other CDW compounds, superconductivity is observed when the CDW order is suppressed via hydrostatic pressure [J. J. Hamlin et al., Phys. Rev. Lett. 102, 177002 (2009)]. What sets the heavier members of the series apart is the observation of a second CDW transition at lower temperatures having an in-plane ordering wave vector of almost the same magnitude but orthogonal to the ordering wave vector observed at higher temperatures [N. Ru et al., Phys. Rev. B 77, 035114 (2008)]. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of In particular, we show that there are several phonon modes along both in-plane directions, which respond to the onset of the CDW transition at . Surprisingly, these soft modes close to show strong softening near but do not exhibit any response to the lower-temperature transition at . Our results indicate that the low-temperature CDW order is not just the 90° rotated analogue of the one appearing at high temperatures.- 12 September 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 98 (9) , 094304
Open AccessCompeting soft phonon modes at the charge-density-wave transitions inThe family of rare-earth () tritellurides features charge-density-wave (CDW) order related to strongly momentum-dependent electron-phonon coupling. Similar to other CDW compounds, superconductivity is observed when the CDW order is suppressed via hydrostatic pressure [J. J. Hamlin et al., Phys. Rev. Lett. 102, 177002 (2009)]. What sets the heavier members of the series apart is the observation of a second CDW transition at lower temperatures having an in-plane ordering wave vector of almost the same magnitude but orthogonal to the ordering wave vector observed at higher temperatures [N. Ru et al., Phys. Rev. B 77, 035114 (2008)]. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of In particular, we show that there are several phonon modes along both in-plane directions, which respond to the onset of the CDW transition at . Surprisingly, these soft modes close to show strong softening near but do not exhibit any response to the lower-temperature transition at . Our results indicate that the low-temperature CDW order is not just the 90° rotated analogue of the one appearing at high temperatures. - 27 August 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 98 (8) , 081116
Determining the local low-energy excitations in the Kondo semimetalusing resonant inelastic x-ray scatteringWe have investigated the local low-energy excitations in , a material discussed recently in the framework of strongly correlated Weyl semimetals, by means of Ce resonant inelastic x-ray scattering (RIXS). The availability of both and excitations of the Ce configuration in the spectra allows for the determination of the crystal-electric field (CEF) parameters that explain quantitatively the high-temperature anisotropy of the magnetic susceptibility. The absence of an azimuthal dependence in the spectra indicates that all CEF states are close to being rotational symmetric. We show further that the non-negligible impact of the parameter on the ground state of leads to a reduction of the magnetic moment due to multiplet intermixing. This improves the agreement between CEF calculations and the experimentally determined magnetic susceptibility considerably at low temperatures. Deviations that persist at low temperatures for fields within the tetragonal plane are attributed to the Kondo interaction between and conduction electrons. The RIXS results are consistent with inelastic neutron scattering data and are compared to the predictions from ab initio based electronic structure calculations.- 27 August 2018
- Published by American Physical Society (APS) in Physical Review B
- Vol. 98 (8) , 081116
Determining the local low-energy excitations in the Kondo semimetalusing resonant inelastic x-ray scatteringWe have investigated the local low-energy excitations in , a material discussed recently in the framework of strongly correlated Weyl semimetals, by means of Ce resonant inelastic x-ray scattering (RIXS). The availability of both and excitations of the Ce configuration in the spectra allows for the determination of the crystal-electric field (CEF) parameters that explain quantitatively the high-temperature anisotropy of the magnetic susceptibility. The absence of an azimuthal dependence in the spectra indicates that all CEF states are close to being rotational symmetric. We show further that the non-negligible impact of the parameter on the ground state of leads to a reduction of the magnetic moment due to multiplet intermixing. This improves the agreement between CEF calculations and the experimentally determined magnetic susceptibility considerably at low temperatures. Deviations that persist at low temperatures for fields within the tetragonal plane are attributed to the Kondo interaction between and conduction electrons. The RIXS results are consistent with inelastic neutron scattering data and are compared to the predictions from ab initio based electronic structure calculations.- Open Access
- 8 June 2016
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 116 (23) , 237003
Strain-Driven Approach to Quantum Criticality inwith, Rb, and CsThe iron-based superconductors with , Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state.- 8 June 2016
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 116 (23) , 237003
Open AccessStrain-Driven Approach to Quantum Criticality inwith, Rb, and CsThe iron-based superconductors with , Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state. - Open Access
Lattice dynamical properties of superconducting SrPt$_3$P studied via inelastic x-ray scattering and density functional perturbation theory
We present a study of the lattice dynamical properties of superconducting SrPt$_3$P ($T_c = 8.4$ K) via high-resolution inelastic x-ray scattering (IXS) and ab initio calculations. Density functional perturbation theory including spin-orbit coupling (SOC) results in enhanced electron-phonon coupling (EPC) for the optic phonon modes originating from the Pt(I) atoms, with energies $\sim 5$ meV, resulting in a large EPC constant $\lambda \sim 2$. An overall softening of the IXS powder spectra occurs from room to low temperatures, consistent with the predicted strong EPC and with recent specific-heat experiments ($2\Delta_0 / k_{\mathrm{B}}T_c \sim 5$). The low-lying phonon modes observed in the experiments are approximately 1.5 meV harder than the corresponding calculated phonon branch. Moreover, we do not find any changes in the spectra upon entering the superconducting phase. We conclude that current theoretical calculations underestimate the energy of the lowest band of phonon modes indicating that the coupling of these modes to the electronic subsystem is overestimated.Open AccessLattice dynamical properties of superconducting SrPt$_3$P studied via inelastic x-ray scattering and density functional perturbation theory
We present a study of the lattice dynamical properties of superconducting SrPt$_3$P ($T_c = 8.4$ K) via high-resolution inelastic x-ray scattering (IXS) and ab initio calculations. Density functional perturbation theory including spin-orbit coupling (SOC) results in enhanced electron-phonon coupling (EPC) for the optic phonon modes originating from the Pt(I) atoms, with energies $\sim 5$ meV, resulting in a large EPC constant $\lambda \sim 2$. An overall softening of the IXS powder spectra occurs from room to low temperatures, consistent with the predicted strong EPC and with recent specific-heat experiments ($2\Delta_0 / k_{\mathrm{B}}T_c \sim 5$). The low-lying phonon modes observed in the experiments are approximately 1.5 meV harder than the corresponding calculated phonon branch. Moreover, we do not find any changes in the spectra upon entering the superconducting phase. We conclude that current theoretical calculations underestimate the energy of the lowest band of phonon modes indicating that the coupling of these modes to the electronic subsystem is overestimated.