Microsecond-pulsed nanocalorimetry: a scalable approach for ultrasensitive heat capacity measurements

We introduce a nanocalorimetric technique based on microsecond-pulsed heating (µs-PHnC) that enables high-sensitivity, quasi-isothermal heat capacity measurements on nanoscale samples. Such resolution is critical for exploring thermodynamic signatures in low-dimensional materials, where conventional techniques fall short. By confining thermal excitation to microsecond timescales, this approach minimizes lateral heat diffusion, reduces heat capacity addenda to below 10⁻⁹ J K^-1, and achieves noise densities as low as 75 pJ K⁻¹ √Hz mm⁻², unlocking precise thermodynamic characterization of subnanogram samples in areas as small as 30 × 30 µm². The method delivers exceptional temperature homogeneity, as demonstrated by resolving sharp phase transitions, such as the antiferromagnetic transition in ultrathin CoO films, with unprecedented clarity. Its quasi-static operation is inherently compatible with external stimuli, including magnetic and electric fields, thereby expanding its utility for in-operando thermodynamic studies. The method is scalable in lateral dimension because the microsecond excitation window confines the thermal diffusion length, allowing the effective calorimetric volume to shrink with the device footprint. This advancement establishes a robust and scalable platform for probing thermal phenomena in nanostructured and low-dimensional materials, significantly broadening the scope of nanocalorimetry.