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Quantum Heat Under the Microscope: A Perspective on Cryogenic Scanning Thermal Microscopy
Authors:
Valentin Fonck,
Jean Spiece,
Pascal Gehring
Abstract:
Exploring thermal transport at cryogenic temperatures presents both significant challenges and valuable insights. By uncovering the thermal counterpart of well-known quantum phenomena, researchers investigated fascinating phenomena ranging from the violation of the Wiedemann-Franz law to the quantisation of phonons. One key frontier remains : no existing method can image local heat transport at th…
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Exploring thermal transport at cryogenic temperatures presents both significant challenges and valuable insights. By uncovering the thermal counterpart of well-known quantum phenomena, researchers investigated fascinating phenomena ranging from the violation of the Wiedemann-Franz law to the quantisation of phonons. One key frontier remains : no existing method can image local heat transport at the nanoscale under cryogenic conditions. In this Perspective, we review the current state state of the art of local heat transport characterisation techniques and highlight their limitations. As a motivation for the development of cryogenic Scanning Thermal Microscopy, we provide five case studies illustrating how this approach could deepen our understanding of exotic quantum phases and enable the emergence of transformative technologies.
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Submitted 2 July, 2026;
originally announced July 2026.
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Direct Nanoscale Pyroelectric Characterization of a CuInP${}_2$S${}_6$ van der Waals Nanogenerator
Authors:
Valentin Fonck,
Roop K. Mech,
Mohammadali Razeghi,
Stuart Finch,
Aljoscha Söll,
Phillip Dobson,
Jonathan R. Weaver,
Zdenek Sofer,
Oleg Kolosov,
Jean Spièce,
Pascal Gehring
Abstract:
Pyroelectric energy conversion offers a route for harvesting time-dependent thermalfluctuations that are abundant in natural and technological environments. Twodimensional ferroelectrics are particularly attractive for this purpose because reduced dimensionality enables ultrathin, mechanically compliant device architectures. Here, we demonstrate direct nanoscale pyroelectric characterization of an…
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Pyroelectric energy conversion offers a route for harvesting time-dependent thermalfluctuations that are abundant in natural and technological environments. Twodimensional ferroelectrics are particularly attractive for this purpose because reduced dimensionality enables ultrathin, mechanically compliant device architectures. Here, we demonstrate direct nanoscale pyroelectric characterization of an out-of-plane van der Waals nanogenerator based on CuInP2S6 (CIPS) encapsulated between few-layer graphene electrodes. A scanning thermal microscopy (SThM) probe is employed as a localized nanoscale heat source while the electrically generated response is measured in situ through the device electrodes. Harmonic detection isolates the pyroelectric signal from parasitic first-harmonic electromechanical contributions, while finite-element thermal modeling combined with probe calibration enables direct determination of the local pyroelectric coefficient from the measured electrical response. Beyond quantitative characterization, the spatially resolved measurements directly identify electrically inactive regions associated with device defects, revealing local performance-limiting features that remain hidden in conventional spatially averaged pyroelectric measurements. The presented approach establishes a versatile platform for quantitative nanoscale pyroelectric characterization and the optimization of van der Waals pyroelectric devices.
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Submitted 22 June, 2026; v1 submitted 15 June, 2026;
originally announced June 2026.
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Characterization of heat transfer in 3D CMOS structures using Sideband Scanning Thermal Wave Microscopy
Authors:
Valentin Fonck,
Mohammadali Razeghi,
Jean Spièce,
Phillip Dobson,
Jonathan Weaver,
George Ridgard,
Grayson M. Noah,
Pascal Gehring
Abstract:
Efficient thermal management is critical for cryogenic CMOS circuits, where local heating can compromise device performance and qubit coherence. Understanding heat flow at the nanoscale in these multilayer architectures requires localized, high-resolution thermal probing techniques capable of accessing buried structures.
Here, we introduce a sideband thermal wave detection scheme for Scanning Th…
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Efficient thermal management is critical for cryogenic CMOS circuits, where local heating can compromise device performance and qubit coherence. Understanding heat flow at the nanoscale in these multilayer architectures requires localized, high-resolution thermal probing techniques capable of accessing buried structures.
Here, we introduce a sideband thermal wave detection scheme for Scanning Thermal Microscopy, S-STWM, to probe deeply buried heater structures within CMOS dies. By extracting the phase of propagating thermal waves, this method provides spatially resolved insight into heat dissipation pathways through complex multilayer structures. Our approach enables quantitative evaluation of thermal management strategies, informs the design of cryo-CMOS circuits, and establishes a foundation for in situ thermal characterization under cryogenic operating conditions.
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Submitted 3 November, 2025; v1 submitted 31 October, 2025;
originally announced October 2025.
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Direct measurement of the local electrocaloric effect in 2D ferroelectric In${}_2$Se${}_3$ by Scanning Electrocaloric Thermometry
Authors:
Jean Spièce,
Valentin Fonck,
Charalambos Evangeli,
Phil S. Dobson,
Jonathan M. R. Weaver,
Pascal Gehring
Abstract:
The electrocaloric effect refers to the temperature change in a material when an electric field is applied or removed. Significant breakthroughs revealed its potential for solid-state cooling technologies in past decades. These devices offer a sustainable alternative to traditional vapor compression refrigeration, with advantages such as compactness, silent operation, and the absence of moving par…
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The electrocaloric effect refers to the temperature change in a material when an electric field is applied or removed. Significant breakthroughs revealed its potential for solid-state cooling technologies in past decades. These devices offer a sustainable alternative to traditional vapor compression refrigeration, with advantages such as compactness, silent operation, and the absence of moving parts or refrigerants.
Electrocaloric effects are typically studied using indirect methods using polarization data, and which suffer from inaccuracies related to assumptions about heat capacity. Direct methods, although more precise, require device fabrication and face challenges in studying meso- or nanoscale systems, like 2D materials, and materials with non-uniform polarization textures where high spatial resolution is required.
In this study, a novel technique, Scanning Electrocaloric Thermometry, is introduced for characterizing the local electrocaloric effect in nanomaterials. This approach achieves high spatial resolution by locally applying electric fields and by simultaneously measuring the resulting temperature change. By employing AC excitation, the measurement sensitivity is further enhanced and the electrocaloric effect is disentangled from other heating mechanisms such as Joule heating and dielectric losses. The effectiveness of the method is demonstrated by examining electrocaloric and heat dissipation phenomena in two-dimensional In${}_2$Se${}_3$ micrometer-sized flakes.
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Submitted 20 December, 2024;
originally announced December 2024.
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Record-high Anomalous Ettingshausen effect in a micron-sized magnetic Weyl semimetal on-chip cooler
Authors:
Mohammadali Razeghi,
Jean Spiece,
Valentin Fonck,
Yao Zhang,
Michael Rohde,
Rikkie Joris,
Philip S. Dobson,
Jonathan M. R. Weaver,
Lino da Costa Pereira,
Simon Granville,
Pascal Gehring
Abstract:
Solid-state cooling devices offer compact, quiet, reliable and environmentally friendly solutions that currently rely primarily on the thermoelectric (TE) effect. Despite more than two centuries of research, classical thermoelectric coolers suffer from low efficiency which hampers wider application. In this study, the less researched Anomalous Ettingshausen effect (AEE), a transverse thermoelectri…
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Solid-state cooling devices offer compact, quiet, reliable and environmentally friendly solutions that currently rely primarily on the thermoelectric (TE) effect. Despite more than two centuries of research, classical thermoelectric coolers suffer from low efficiency which hampers wider application. In this study, the less researched Anomalous Ettingshausen effect (AEE), a transverse thermoelectric phenomenon, is presented as a new approach for on-chip cooling. This effect can be boosted in materials with non-trivial band topologies as demonstrated in the Heusler alloy $\text{Co}_2\text{MnGa}$. Enabled by the high quality of our material, in situ scanning thermal microscopy experiments reveal a record-breaking anomalous Ettingshausen coefficient of $-2.1$~mV in $μ$m-sized on-chip cooling devices at room temperature. A significant 44\% of the effect is contributed by the intrinsic topological properties, in particular the Berry curvature of $\text{Co}_2\text{MnGa}$, emphasising the unique potential of magnetic Weyl semimetals for high-performance spot cooling in nanostructures.
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Submitted 20 March, 2024;
originally announced March 2024.