Specific Heat of Lead in the Range from 2 to 8°K

Neighbor, J. E.; Cochran, J. F.; Shiffman, C. A.

doi:10.1103/physrev.155.384

Cited by 47 publications

(8 citation statements)

References 13 publications

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“…The zero field superconducting transition displayed in Fig. 2b, has a 20 mK width and no upturn in C. From the step height ∆C = 0.754 nJ/K at T c and the Sommerfeld term γ, we find ∆C/γT c = 2.68 in agreement with the values obtained from magnetic [8] and other calorimetric [7,9] measurements. The normalized slope of the specific heat discontinuity at T c is an indicator of the coupling strength of the superconductor.…”

Section: Resultssupporting

confidence: 86%

Absolute specific heat measurements of a microgram Pb crystal using ac nanocalorimetry

Tagliati

Rydh

2012

J. Phys.: Conf. Ser.

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Absolute specific heat measurements of a microgram Pb crystal using ac nanocalorimetry Abstract. Heat capacity measurements using the ac steady state method are often considered difficult to provide absolute accuracy. By adjusting the working frequency to maintain a constant phase and using the phase information to obtain the heat capacity, we have found that it is possible to achieve good absolute accuracy. Here we present a thermodynamic study of a ∼ 2.6 µg Pb superconducting crystal to demonstrate the newly opened capabilities. The sample is measured using a differential membrane-based calorimeter. The custom-made calorimetric cell is a pile of thin film Ti heater, insulation layer and Ge1−xAux thermometer fabricated in the center of two Si3N4 membranes. It has a background heat capacity < 100 nJ/K at 300 K, decreasing to 9 pJ/K at 1 K. The sample is characterized at temperatures down to 0.5 K. The zero field transition at Tc = 7.21 K has a width ≈ 20 mK and displays no upturn in C. From the heat capacity jump at Tc and the extrapolated Sommerfeld term we find ∆C/γTc = 2.68. The latent heat curve obtained from the zero field heat capacity measurement, and the deviations of the thermodynamic critical field from the empirical expression Hc = Hc(0) 1 − (T /Tc) 2 are discussed. Both analyses give results in good agreement with literature. IntroductionCalorimetry is a powerful tool that allows complete thermodynamic characterization of materials. In particular, nanocaloric measurements are suitable to study phase transitions and specific heat dependencies of new superconductors, often available in just µg quantities. In the past two decades much attention was devoted to studies of high-T c superconductors [1] and, more recently, the iron-based superconductors [2]. The electronic specific heat is one of the crucial parameters for understanding high-temperature superconductivity, but it is very hard to measure with good absolute accuracy. Furthermore, it represents just a fraction of the total heat capacity and therefore requires high resolution techniques. The AC steady state method [3] is a very sensitive technique which usually gives only relative heat capacity values [1] because of the difficulties related to the choice of the working frequency. In this method, a certain power P 0 sin ωt modulates the temperature of sample and calorimetric cell that oscillate with amplitude T ac,0 and a phase lag φ. The heat capacity is given by [4]:

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Section: Resultssupporting

confidence: 86%

Absolute specific heat measurements of a microgram Pb crystal using ac nanocalorimetry

Tagliati

Rydh

2012

J. Phys.: Conf. Ser.

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“…There is a weak pressure dependence here in this ratio that is not expected with a simple BCS picture where △γ c /γ n = 1.55. Direct specific heat measurements at ambient pressure have variously obtained △γ c = 7.33 ±0.3 mJ/(mol K 2 ) (Clement and Quinnel 19 ), 7.96 ±0.08 mJ/(mol K 2 ) (Shiffman et al 20 ) and 8.13 ±0.13 mJ/(mol K 2 ) (Neighbor et al 21 ) in good agreement with our ambient result. Combining with the measurement by Horowitz et al 1 of γ n = 3.13 mJ/(mol K 2 ) gives △γ c /γ n = 2.34, 2.54 and 2.60, again in good agreement with our present ambient-pressure result.…”

Section: Fig 5: (Color)supporting

confidence: 91%

Thermodynamic properties of Pb determined from pressure-dependent critical-field measurements

Suresh

Tallon

2007

Phys. Rev. B

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We have carried out extensive low-temperature (1.5 to 10 K) measurements of the critical field, Hc, for the element Pb up to a pressure of P = 1.2 GPa. From this data the electronic entropy, specific heat, thermal expansion coefficient and compressibility is calculated as a function of temperature, pressure and magnetic field. The zero-field data is consistent with direct thermodynamic measurements and the P -dependence of Tc and specific heat coefficient, γ(T, P ) allows the determination of the P -dependence of the pairing interaction.

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“…The coherence length can be calculated by using the Ginzburg-Landau formula ξ GL (0) = (φ 0 /2πH c2 (0)) 1/2 , where φ 0 =h/2e and is found to be ξ GL (0) = 629Å. ∆C/γT c = 1.95, higher than the BCS value of 1.43, but lower than that of elemental Pb [20]. Assuming µ * = 0.13, the electron-phonon coupling constant (λ ep ) can then be calculated from the inverted McMillan's formula [21]:…”

Section: Resultsmentioning

confidence: 99%

Dirac metal to topological metal transition at a structural phase change inAu2Pband prediction ofZ2topology for the superconductor

et al. 2015

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Abstract3D Dirac semi-metals (DSMs) are materials that have massless Dirac electrons and exhibit exotic physical properties. It has been suggested that structurally distorting a DSM can create a Topological Insulator but this has not yet been experimentally verified. Further, Majorana Fermions have been theoretically proposed to exist in materials that exhibit both superconductivity and topological surface states. Here we show that the cubic Laves phase Au 2 Pb has a bulk Dirac cone that is predicted to gap on cooling through a structural phase transition at 100 K. The low temperature phase can be assigned a Z 2 = -1 topological index, and this phase becomes superconducting below 1.2 K. These characteristics make Au 2 Pb a unique platform for studying the transition between bulk Dirac electrons and topological surface states as well as studying the interaction of superconductivity with topological surface states, combining many different properties of emergent materials -superconductivity, bulk Dirac electrons, and a topologically non trivial Z 2 invariant.

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Specific Heat of Lead in the Range from 2 to 8°K

Cited by 47 publications

References 13 publications

Absolute specific heat measurements of a microgram Pb crystal using ac nanocalorimetry

Absolute specific heat measurements of a microgram Pb crystal using ac nanocalorimetry

Thermodynamic properties of Pb determined from pressure-dependent critical-field measurements

Dirac metal to topological metal transition at a structural phase change inAu2Pband prediction ofZ2topology for the superconductor

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