Michele Simoncelli

@cam.ac.uk

Patricia Crone Research Fellow, Gonville & Caius College, Cavendish Laboratory, Theory of Condensed Matter Group
University of Cambridge

Michele Simoncelli


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https://researchid.co/michelesimoncelli

RESEARCH, TEACHING, or OTHER INTERESTS

Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Fluid Flow and Transfer Processes
17

Scopus Publications

1600

Scholar Citations

11

Scholar h-index

11

Scholar i10-index

Scopus Publications

  • Viscous Heat Backflow and Temperature Resonances in Extreme Thermal Conductors
    Jan Dragašević, Bogdan Rajkov, Michele Simoncelli
    Physical Review Letters, 2026
    We demonstrate that nondiffusive, fluidlike heat transport, such as heat backflowing from cooler to warmer regions, can be induced, controlled, and amplified in extreme thermal conductors such as graphite and hexagonal boron nitride. We employ the viscous heat equations, i.e., the thermal counterpart of the Navier-Stokes equations in the laminar regime, to show with first-principles quantitative accuracy that a finite thermal viscosity yields steady-state heat vortices, and governs the magnitude of transient temperature waves. Finally, we devise strategies that exploit devices’ boundaries and resonance to amplify and control heat hydrodynamics, paving the way for novel experiments and applications in next-generation electronic and phononic technologies.
  • Imaging Heat Transport in Suspended Diamond Nanostructures with Integrated Spin Defect Thermometers
    V. Goblot, K. Wu, E. Di Lucente, Y. Zhu, E. Losero, Q. Jobert, C. Jaramillo Concha, N. Quack, N. Marzari, M. Simoncelli, C. Galland
    Physical Review Letters, 2026
  • Heat transport in crystalline organic semiconductors: coexistence of phonon propagation and tunneling
    Lukas Legenstein, Lukas Reicht, Sandro Wieser, Michele Simoncelli, Egbert Zojer
    Npj Computational Materials, 2025
    Understanding heat transport in organic semiconductors is of fundamental and practical relevance. Therefore, we study the lattice thermal conductivities of a series of (oligo)acenes, where an increasing number of rings per molecule leads to a systematic increase of the crystals’ complexity. Temperature-dependent thermal conductivity experiments in these systems disagree with predictions based on the traditional Peierls–Boltzmann framework, which describes heat transport in terms of particle-like phonon propagation. We demonstrate that accounting for additional phonon-tunneling conduction mechanisms through the Wigner Transport Equation resolves this disagreement and quantitatively rationalizes experiments. The pronounced increase of tunneling transport with temperature explains several unusual experimental observations, such as a weak temperature dependence in naphthalene’s thermal conductivity and an essentially temperature-invariant conductivity in pentacene. While the anisotropic thermal conductivities within the acene planes are essentially material-independent, the tunneling contributions (and hence the total conductivities) significantly increase with molecular length in the molecular backbone direction. This, for pentacene results in a surprising minimum of the thermal conductivity at 300 K.
  • Defect-tolerant electron and defect-sensitive phonon transport in quasi-2D conjugated coordination polymers
    Hio-Ieng Un, Kamil Iwanowski, Jordi Ferrer Orri, Ian E. Jacobs, Naoya Fukui, et al.
    Nature Communications, 2025
    Thermoelectric materials, enabling direct waste-heat to electricity conversion, need to be highly electrically conducting while simultaneously thermally insulating. This is fundamentally challenging since electrical and thermal conduction usually change in tandem. In quasi-two-dimensional conjugated coordination polymer films we discover an advantageous thermoelectric transport regime, in which charge transport is defect-tolerant but heat propagation is defect-sensitive; it imparts the ideal mix of antithetical properties—temperature-activated, exceptionally low lattice thermal conductivities of 0.2 W m −1 K −1 below Kittel’s limit originating from small-amplitude, quasi-harmonic lattice dynamics with disorder-limited lifetimes and vibrational scattering length on the order of interatomic spacing, and high electrical conductivities up to 2000 S cm −1 with metallic temperature dependence, notably in poorly crystalline structures with paracrystallinity >10%. These materials offer attractive properties, such as ease of processing and defect tolerance, for applications, that require fast charge, but slow heat transport.
  • Bond-Network Entropy Governs Heat Transport in Coordination-Disordered Solids
    Kamil Iwanowski, Gábor Csányi, Michele Simoncelli
    Physical Review X, 2025
    Understanding how the vibrational and thermal properties of solids are influenced by atomistic structural disorder is of fundamental scientific interest and paramount to designing materials for next-generation energy technologies. While several studies indicate that structural disorder strongly influences the thermal conductivity, the fundamental physics governing the disorder-conductivity relation remains elusive. Here we show that order-of-magnitude, disorder-induced variations of conductivity in network solids can be predicted from a “bond-network” entropy, an atomistic structural descriptor that quantifies heterogeneity in the topology of the atomic-bond network. We employ the Wigner formulation of thermal transport to demonstrate the existence of a relation between the bond-network entropy and observables such as smoothness of the vibrational density of states and macroscopic conductivity. We also show that the smoothing of the vibrational density of states encodes information about the thermal resistance induced by disorder and can be directly related to phenomenological models for phonon-disorder scattering based on the semiclassical Peierls-Boltzmann equation. Our findings rationalize the conductivity variations of disordered carbon polymorphs ranging from nanoporous electrodes to defective graphite used as a moderator in nuclear reactors.
  • Lattice distortion leads to glassy thermal transport in crystalline Cs3Bi2I6Cl3
    Zezhu Zeng, Zheyong Fan, Michele Simoncelli, Chen Chen, Ting Liang, Yue Chen, Geoff Thornton, Bingqing Cheng
    Proceedings of the National Academy of Sciences of the United States of America, 2025
    The glassy thermal conductivities observed in crystalline inorganic perovskites such as Cs 3 Bi 2 I 6 Cl 3 are perplexing and lacking theoretical explanations. Here, we first experimentally measure its thermal transport behavior from 20 to 300 K, after synthesizing Cs 3 Bi 2 I 6 Cl 3 single crystals. Using path-integral molecular dynamics simulations driven by machine learning potentials, we reveal that Cs 3 Bi 2 I 6 Cl 3 has large lattice distortions at low temperatures, which may be related to the large atomic size mismatch. Employing the Wigner formulation of thermal transport, we reproduce the experimental thermal conductivities based on lattice-distorted structures. This study thus provides a framework for predicting and understanding glassy thermal transport in materials with strong lattice disorder.
  • Thermal Transport of Amorphous Hafnia Across the Glass Transition
    Zezhu Zeng, Xia Liang, Zheyong Fan, Yue Chen, Michele Simoncelli, Bingqing Cheng
    ACS Materials Letters, 2025
    Heat transport in glasses across a wide range of temperature is vital for applications in gate dielectrics and heat insulator. However, it remains poorly understood due to the challenges of modeling vibrational anharmonicity below glass transition temperature and capturing configurational dynamics across the transition. Interestingly, recent calculations predicted that amorphous hafnia (a-HfO$_2$) exhibits an unusual drop in thermal conductivity ($\\kappa$) with temperature, contrasting with the typical rise or saturation observed in glasses upon heating. Using molecular dynamics simulations with a machine-learning-based neuroevolution potential, we compute the vibrational properties and $\\kappa$ of a-HfO$_2$ from 50~K to 2000~K. At low temperatures, we employ the Wigner transport equation to incorporate both anharmonicity and Bose-Einstein statistics of atomic vibration in the calculation of $\\kappa$. At above 1200~K, atomic diffusion breaks down the Lorentzian-shaped quasiparticle picture and makes the lattice-dynamics treatment invalid. We thus use molecular dynamics with the Green-Kubo method to capture convective heat transport in a-HfO$_2$ near the glass transition at around 1500~K. Additionally, by extending the Wigner transport equation to supercooled liquid states, we find the crucial role of low-frequency modes in facilitating heat convection. The computed $\\kappa$ of a-HfO$_2$, based on both Green-Kubo and Wigner transport theories, reveals a continuous increase with temperature up to 2000~K.
  • Temperature-invariant crystal–glass heat conduction: From meteorites to refractories
    Michele Simoncelli, Daniele Fournier, Massimiliano Marangolo, Etienne Balan, Keevin Béneut, et al.
    Proceedings of the National Academy of Sciences of the United States of America, 2025
    The thermal conductivities of crystals and glasses vary strongly and with opposite trends upon heating, decreasing in crystals and increasing in glasses. Here, we show that the dominant conduction mechanisms of crystals (particle-like propagation) and glasses (wave-like tunneling) can compensate in materials with crystalline bond order and nearly glassy bond geometry, yielding a hybrid crystal–glass conductivity that is constant from the quantum to the classical regime (i.e., from below to above the Debye temperature). We showcase these arguments with a combined theoretical and experimental study on meteoritic silica (a tridymite carved from a sample found in Steinbach, Germany, in 1724) and on a geometrically amorphous tridymite phase found in refractory bricks used in furnaces for steel smelting. Our results prove that temperature-invariant conductivities are not limited to the classical regime, and pave the way to understand or control heat-transport phenomena in solids exposed to extreme temperature variations, ranging from planetary cooling to heating protocols to reduce the carbon footprint of industrial furnaces.
  • First-principles characterization of thermal conductivity in LaPO4 -based alloys
    Anees Pazhedath, Lorenzo Bastonero, Nicola Marzari, Michele Simoncelli
    Physical Review Applied, 2024
    Alloys based on lanthanum phosphate (LaPO4) are often employed as thermal barrier coatings, due to their low thermal conductivity and structural stability over a wide temperature range. To enhance the thermal-insulation performance of these alloys, it is essential to comprehensively understand the fundamental physics governing their heat conduction. Here, we employ the Wigner formulation of thermal transport in conjunction with first-principles calculations to elucidate how the interplay between anharmonicity and compositional disorder determines the thermal properties of La1−xGdxPO4 alloys, and discuss the fundamental physics underlying the emergence and coexistence of particlelike and wavelike heat-transport mechanisms. We also show how the Wigner transport equation correctly describes the thermodynamic limit of a compositionally disordered crystal, while the Boltzmann transport equation does not. Our predictions for microscopic vibrational properties (temperature-dependent Raman spectrum) and for macroscopic thermal conductivity are validated against experiments. Finally, we leverage these findings to devise strategies to optimize the performance of thermal barrier coatings. Published by the American Physical Society 2024
  • Vibrational and thermal properties of amorphous alumina from first principles
    Angela F. Harper, Kamil Iwanowski, William C. Witt, Mike C. Payne, Michele Simoncelli
    Physical Review Materials, 2024
    Amorphous alumina is employed ubiquitously as a high-dielectric-constant material in electronics, and its thermal-transport properties are of key relevance for heat management in electronic chips and devices. Experiments show that the thermal conductivity of alumina depends significantly on the synthesis process, indicating the need for a theoretical study to elucidate the atomistic origin of these variations. Here we employ first-principles simulations to characterize the atomistic structure, vibrational properties, and thermal conductivity of alumina at densities ranging from 2.28 g/cm3 to 3.49 g/cm3. Moreover, using an interatomic potential trained on first-principles data, we investigate how system size affects predictions of the thermal conductivity, showing that simulations containing 120 atoms can already reproduce the bulk limit of the conductivity. Finally, relying on the recently developed Wigner formulation of thermal transport, we shed light on the interplay between atomistic topological disorder and anharmonicity in the context of heat conduction, showing that the former dominates over the latter in determining the conductivity of alumina.
  • Thermal conductivity of glasses: first-principles theory and applications
    Michele Simoncelli, Francesco Mauri, Nicola Marzari
    Npj Computational Materials, 2023
  • Crossover from Boltzmann to Wigner thermal transport in thermoelectric skutterudites
    Enrico Di Lucente, Michele Simoncelli, Nicola Marzari
    Physical Review Research, 2023
  • Wigner Formulation of Thermal Transport in Solids
    Michele Simoncelli, Nicola Marzari, Francesco Mauri
    Physical Review X, 2022
  • Many-body Green's function approach to lattice thermal transport
    Giovanni Caldarelli, Michele Simoncelli, Nicola Marzari, Francesco Mauri, Lara Benfatto
    Physical Review B, 2022
  • Generalization of Fourier's Law into Viscous Heat Equations
    Michele Simoncelli, Nicola Marzari, Andrea Cepellotti
    Physical Review X, 2020
  • Unified theory of thermal transport in crystals and glasses
    Michele Simoncelli, Nicola Marzari, Francesco Mauri
    Nature Physics, 2019
  • Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models
    Michele Simoncelli, Nidhal Ganfoud, Assane Sene, Matthieu Haefele, Barbara Daffos, Pierre-Louis Taberna, Mathieu Salanne, Patrice Simon, Benjamin Rotenberg
    Physical Review X, 2018

RECENT SCHOLAR PUBLICATIONS

  • Lattice thermal transport from phonon spectra beyond perturbation theory
    Z Zeng, M Simoncelli, DE Manolopoulos
    arXiv preprint arXiv:2604.19615 , 2026
    2026
  • Phonon collisional broadening and heat transport beyond the Boltzmann equation
    E Di Lucente, N Marzari, M Simoncelli
    arXiv preprint arXiv:2603.16753 , 2026
    2026
  • Coupled electron-phonon hydrodynamics and viscous thermoelectric equations
    J Coulter, B Rajkov, M Simoncelli
    https://arxiv.org/abs/2503.07560 , 2026
    2026
    Citations: 1
  • Imaging heat transport in suspended diamond nanostructures with integrated spin defect thermometers
    V Goblot, K Wu, E Di Lucente, Y Zhu, E Losero, Q Jobert, ...
    Physical Review Letters 136 (https://doi.org/10.1103/3s96-7ghm), 126304 , 2026
    2026
    Citations: 3
  • Viscous heat backflow and temperature resonances in extreme thermal conductors
    J Dragašević, B Rajkov, M Simoncelli
    Physical Review Letters 136, 186302 , 2026
    2026
    Citations: 3
  • Lattice distortion leads to glassy thermal transport in crystalline Cs Bi I Cl
    Z Zeng, Z Fan, M Simoncelli, C Chen, T Liang, Y Chen, G Thornton, ...
    Proceedings of the National Academy of Sciences 122 (41), e2415664122 , 2025
    2025
    Citations: 8
  • Thermal transport of amorphous hafnia across the glass transition
    Z Zeng, X Liang, Z Fan, Y Chen, M Simoncelli, B Cheng
    ACS Materials Letters 7 (8), 2695-2701 , 2025
    2025
    Citations: 7
  • Anharmonic-Thermal transport package for Quantum ESPRESSO
    L Paulatto, R Sen, A Ciavatta, IB Garba, C Bouillaguet, G Fugallo, ...
    2025
  • Origins of thermal-conductivity anomalies in solids with controlled atomic disorder
    M Simoncelli
    SMT 2025 , 2025
    2025
  • Bond-network entropy controls thermal conductivity of coordination-disordered solids
    K Iwanowski, G Csanyi, M Simoncelli
    SMT 2025 , 2025
    2025
  • Bond-Network Entropy Governs Heat Transport in Coordination-Disordered Solids
    K Iwanowski, G Csányi, M Simoncelli
    Iwanowski, Csányi, Simoncelli, Physical Review X 15, 041041, 2025 , 2025
    2025
    Citations: 7
  • Heat transport in crystalline organic semiconductors: coexistence of phonon propagation and tunneling
    L Legenstein, L Reicht, S Wieser, M Simoncelli, E Zojer
    npj computational materials , 2025
    2025
    Citations: 8
  • Defect-tolerant electron and defect-sensitive phonon transport in quasi-2D conjugated coordination polymers
    HI Un, K Iwanowski, J Ferrer Orri, IE Jacobs, N Fukui, D Cornil, ...
    Nature Communications 16, 6628 , 2025
    2025
    Citations: 6
  • Temperature-invariant crystal–glass heat conduction: From meteorites to refractories
    M Simoncelli, D Fournier, M Marangolo, E Balan, K Béneut, B Baptiste, ...
    Proceedings of the National Academy of Sciences 122 (28) , 2025
    2025
    Citations: 15
  • Hydrodynamic Heat Transport Modeling: Continuum Models and the BTE
    A Sokolov, J Haibeh, M Simoncelli, S Huberman
    APS March Meeting Abstracts 2024, OD01. 094 , 2024
    2024
  • Thermal Conductivity Predictions with Foundation Atomistic Models
    B Pota, P Ahlawat, G Csanyi, M Simoncelli
    https://arxiv.org/pdf/2408.00755 , 2024
    2024
    Citations: 45
  • First-principles characterization of thermal conductivity in LaPO4-based alloys
    A Pazhedath, L Bastonero, N Marzari, M Simoncelli
    Physical Review Applied 22, 024064 , 2024
    2024
    Citations: 18
  • Vibrational and thermal properties of amorphous alumina from first principles
    A Harper, K Iwanowski, C Witt, M Payne, M Simoncelli
    Physical Review Materials 8, 043601 , 2024
    2024
    Citations: 21
  • Thermal conductivity of glasses: First-principles theory and applications
    M Simoncelli, F Mauri, N Marzari
    npj Computational Materials 9 (1), 106 , 2023
    2023
    Citations: 75
  • Modern theory of thermal transport in solids
    M Simoncelli, N Marzari
    Joint Annual Meeting of the Swiss Physical Society and the Austrian Physical … , 2023
    2023

MOST CITED SCHOLAR PUBLICATIONS

  • Unified theory of thermal transport in crystals and glasses
    M Simoncelli, N Marzari, F Mauri
    Nature Physics 15 (8), 809-813 , 2019
    2019
    Citations: 712
  • Wigner formulation of thermal transport in solids
    M Simoncelli, N Marzari, F Mauri
    Physical Review X 12, 041011 (2022) , 2022
    2022
    Citations: 300
  • Generalization of Fourier's law into viscous heat equations
    M Simoncelli, N Marzari, A Cepellotti
    Physical Review X 10 (011019), DOI: 10.1103/PhysRevX.10.011019 , 2020
    2020
    Citations: 135
  • Blue energy and desalination with nanoporous carbon electrodes: Capacitance from molecular simulations to continuous models
    M Simoncelli, N Ganfoud, A Sene, M Haefele, B Daffos, PL Taberna, ...
    Physical Review X 8 (2), 021024 , 2018
    2018
    Citations: 94
  • Many-body Green's function approach to lattice thermal transport
    G Caldarelli, M Simoncelli, N Marzari, F Mauri, L Benfatto
    Physical Review B , 2022
    2022
    Citations: 78
  • Thermal conductivity of glasses: First-principles theory and applications
    M Simoncelli, F Mauri, N Marzari
    npj Computational Materials 9 (1), 106 , 2023
    2023
    Citations: 75
  • Crossover from Boltzmann to Wigner thermal transport in thermoelectric skutterudites
    E Di Lucente, M Simoncelli, N Marzari
    Physical Review Research 5, 033125 , 2023
    2023
    Citations: 59
  • Thermal Conductivity Predictions with Foundation Atomistic Models
    B Pota, P Ahlawat, G Csanyi, M Simoncelli
    https://arxiv.org/pdf/2408.00755 , 2024
    2024
    Citations: 45
  • Vibrational and thermal properties of amorphous alumina from first principles
    A Harper, K Iwanowski, C Witt, M Payne, M Simoncelli
    Physical Review Materials 8, 043601 , 2024
    2024
    Citations: 21
  • First-principles characterization of thermal conductivity in LaPO4-based alloys
    A Pazhedath, L Bastonero, N Marzari, M Simoncelli
    Physical Review Applied 22, 024064 , 2024
    2024
    Citations: 18
  • Temperature-invariant crystal–glass heat conduction: From meteorites to refractories
    M Simoncelli, D Fournier, M Marangolo, E Balan, K Béneut, B Baptiste, ...
    Proceedings of the National Academy of Sciences 122 (28) , 2025
    2025
    Citations: 15
  • Lattice distortion leads to glassy thermal transport in crystalline Cs Bi I Cl
    Z Zeng, Z Fan, M Simoncelli, C Chen, T Liang, Y Chen, G Thornton, ...
    Proceedings of the National Academy of Sciences 122 (41), e2415664122 , 2025
    2025
    Citations: 8
  • Heat transport in crystalline organic semiconductors: coexistence of phonon propagation and tunneling
    L Legenstein, L Reicht, S Wieser, M Simoncelli, E Zojer
    npj computational materials , 2025
    2025
    Citations: 8
  • Thermal transport of amorphous hafnia across the glass transition
    Z Zeng, X Liang, Z Fan, Y Chen, M Simoncelli, B Cheng
    ACS Materials Letters 7 (8), 2695-2701 , 2025
    2025
    Citations: 7
  • Bond-Network Entropy Governs Heat Transport in Coordination-Disordered Solids
    K Iwanowski, G Csányi, M Simoncelli
    Iwanowski, Csányi, Simoncelli, Physical Review X 15, 041041, 2025 , 2025
    2025
    Citations: 7
  • Defect-tolerant electron and defect-sensitive phonon transport in quasi-2D conjugated coordination polymers
    HI Un, K Iwanowski, J Ferrer Orri, IE Jacobs, N Fukui, D Cornil, ...
    Nature Communications 16, 6628 , 2025
    2025
    Citations: 6
  • Thermal transport beyond Fourier, and beyond Boltzmann
    M Simoncelli
    EPFL , 2021
    2021
    Citations: 5
  • Imaging heat transport in suspended diamond nanostructures with integrated spin defect thermometers
    V Goblot, K Wu, E Di Lucente, Y Zhu, E Losero, Q Jobert, ...
    Physical Review Letters 136 (https://doi.org/10.1103/3s96-7ghm), 126304 , 2026
    2026
    Citations: 3
  • Viscous heat backflow and temperature resonances in extreme thermal conductors
    J Dragašević, B Rajkov, M Simoncelli
    Physical Review Letters 136, 186302 , 2026
    2026
    Citations: 3
  • Coupled electron-phonon hydrodynamics and viscous thermoelectric equations
    J Coulter, B Rajkov, M Simoncelli
    https://arxiv.org/abs/2503.07560 , 2026
    2026
    Citations: 1