On the problem of thermal link resistances in a.c. calorimetry

Velichkov, I.V.

doi:10.1016/0011-2275(92)90366-i

Cited by 16 publications

(14 citation statements)

References 9 publications

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“…For most of the data, the raw heat capacity C raw was then obtained as C raw = [P/(2ω H T ac )] sin φ ac , where P is the a.c. heat flow produced by the heater and ω H is the frequency of the heater current. Multiplication by the factor sin φ ac allows for more accurate evaluation of the heat capacity, even for smaller frequencies 28 . Notice that the frequency of the temperature oscillation is two times higher than ω H .…”

Section: Methodsmentioning

confidence: 99%

Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

et al. 2016

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In condensed matter physics, spontaneous symmetry breaking has been a key concept, and discoveries of new types of broken symmetries have greatly increased our understanding of matter 1,2 . Recently, electronic nematicity, novel spontaneous rotational-symmetry breaking leading to an emergence of a special direction in electron liquids, has been attracting significant attention 3-6 . Here, we show bulk thermodynamic evidence for nematic superconductivity, in which the nematicity emerges in the superconducting gap amplitude, in Cu x Bi 2 Se 3 . Based on high-resolution calorimetry of single-crystalline samples under accurate two-axis control of the magnetic field direction, we discovered clear two-fold symmetry in the specific heat and in the upper critical field despite the trigonal symmetry of the lattice. Nematic superconductivity for this material should possess a unique topological nature associated with odd parity 7-9 . Thus, our findings establish a new class of spontaneously symmetry-broken states of matter-namely, odd-parity nematic superconductivity.

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Section: Methodsmentioning

confidence: 99%

Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

et al. 2016

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“…Discretized thermal modelling is well established for AC calorimetry [9][10][11] and provides good intuition and semi quantitative understanding of thermal experiments. Figure 3(a) shows the full discretized thermal model for our experiment described above.…”

Section: Discretized Thermal Modellingmentioning

confidence: 99%

AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions

Ikeda

Straquadine

Hristov

et al. 2019

Review of Scientific Instruments

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Studying the response of materials to strain can elucidate subtle properties of electronic structure in strongly correlated materials. So far, mostly the relation between strain and resistivity, the so called elastoresistivity, has been investigated. The elastocaloric effect is a second rank tensor quantity describing the relation between entropy and strain. In contrast to the elastoresistivity, the elastocaloric effect is a thermodynamic quantity. Experimentally, elastocaloric effect measurements are demanding since the thermodynamic conditions during the measurement have to be well controlled. Here we present a technique to measure the elastocaloric effect under quasi adiabatic conditions. The technique is based on oscillating strain, which allows for increasing the frequency of the elastocaloric effect above the thermal relaxation rate of the sample. We apply the technique to Co-doped iron pnictide superconductors and show that the thermodynamic signatures of second order phase transitions in the elastocaloric effect closely follow those observed in calorimetry experiments. In contrast to the heat capacity, the electronic signatures in the elastocaloric effect are measured against a small phononic background even at high temperatures, establishing this technique as a powerful complimentary tool for extracting the entropy landscape proximate to a continuous phase transition.

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“…This technique was improved by Velichkov [78] who supported the sample by a membrane (see Figure 17). Here the heater is coupled to the membrane in the form of a deposited thin layer of high resistivity material in good thermal contact with the substrate and of negligible heat capacity.…”

Section: Migration To Helium-cooled Devicementioning

confidence: 99%

“…In vacuum the membrane provides the only heat loss path, thus the membrane geometry determines the heat flow. Efforts to describe the sensor with a simple analytical model, following references [78,80], failed as the structure of the sensor seems to be too complicated. Additionally a semi-analytical approach considering the membrane as a series of electrical low passes with thermal resistances treated as electrical resistances and heat capacities treated as electrical capacitances (see Figure 28) lead to no success.…”

Section: Heat Capacity Determinationmentioning

confidence: 99%

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

Ahrenberg

Chua

Whitaker

et al. 2013

The Journal of Chemical Physics

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Vapor-deposited glasses of toluene and ethylbenzene have been characterized by in situ ac chip-nanocalorimetry. The high sensitivity of this method allows the detection of small changes in the heat capacity of nanogram size samples. We observe that vapor-deposited glasses have up to 4% lower heat capacities than the ordinary glass. The largest heat capacity decrease and the most kinetically stable glasses of toluene and ethylbenzene are observed in a range of deposition temperatures between 0.75 Tg and 0.96 Tg. Compared to larger molecules, deposition rate has a minor influence on the kinetic stability of these glasses. For both toluene and ethylbenzene, the kinetic stability is strongly correlated with the heat capacity decrease for deposition temperatures above 0.8 Tg. In addition, ac-nanocalorimetry was used to follow the isothermal transformation of the stable glasses into the supercooled liquid at temperatures slightly above Tg. Toluene and ethylbenzene stable glasses exhibit a constant transformation rate which is consistent with the growth front mechanism recently demonstrated for tris-naphthylbenzene and indomethacin. The kinetic stability of the most stable toluene and ethylbenzene glasses is comparable to that observed for other stable glasses formed by vapor deposition.

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On the problem of thermal link resistances in a.c. calorimetry

Cited by 16 publications

References 9 publications

Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

Thermodynamic evidence for nematic superconductivity in CuxBi2Se3

AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

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