Specific Heat of Superconducting Zn Nanowires

Kurtz, James S.; Johnson, Robert R.; Tian, Mingliang; Kumar, Nitesh; Zhi-gang, MA; Xu, Shengyong; Chan, Moses H. W.

doi:10.1103/physrevlett.98.247001

Cited by 18 publications

(14 citation statements)

References 28 publications

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“…For thicker mesoscopic wires with D > 20 nm, the role of any given quasiparticle branch becomes much less significant, and quantum-size oscillations in the superconducting properties are strongly reduced. In this regime we recover the smooth superconducting-to-normal transition in agreement with the previous theoretical results 16 and recent experimental observations 1,17,21 .…”

Section: Effect Of Thicknesssupporting

confidence: 91%

Magnetic-field induced quantum-size cascades in superconducting nanowires

2008

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In high-quality nanowires, quantum confinement of the transverse electron motion splits the band of single-electron states in a series of subbands. This changes in a qualitative way the scenario of the magnetic-field induced superconductor-to-normal transition. We numerically solve the Bogoliubovde Gennes equations for a clean metallic cylindrical nanowire at zero temperature in a parallel magnetic field and find that for diameters D 10 ÷ 15 nm, this transition occurs as a cascade of subsequent jumps in the order parameter (this is opposed to the smooth second-order phase transition in the mesoscopic regime). Each jump is associated with the depairing of electrons in one of the single-electron subbands. As a set of subbands contribute to the order parameter, the depairing process occurs as a cascade of jumps. We find pronounced quantum-size oscillations of the critical magnetic field with giant resonant enhancements. In addition to these orbital effects, the paramagnetic breakdown of Cooper pairing also contributes but only for smaller diameters, i. e., D 5 nm.

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Section: Effect Of Thicknesssupporting

confidence: 91%

Magnetic-field induced quantum-size cascades in superconducting nanowires

2008

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“…An interesting question hence arises: what should the behavior of an array of aligned and weakly coupled superconducting nanowires be? This question is relevant because with today's nanofabrication facilities, thin superconducting nanowires [3][4][5][6][7][8] and nanowire arrays [9][10][11][12] can be tailored, and an understanding of how a phase-coherent superconducting state can be achieved in a nanoscale electronic circuit is of fundamental interest.…”

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confidence: 99%

Dimensional crossover transition in a system of weakly coupled superconducting nanowires

et al. 2012

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Owing to recent observations of superconductivity in quasi-onedimensional (1D) systems, Josephson arrays composed of aligned and weakly coupled 1D superconducting nanowires have attracted renewed interest for modeling the experimental data. Carrying out Monte Carlo simulations, we go beyond the traditional mean field results to show that the competition between 1D fluctuations and the transverse Josephson coupling between the nanowires can lead to a 1D-3D crossover transition at a temperature T c below the mean field T O C of the wires, with interesting and surprising pre-transitional characteristics. In particular, the specific heat exhibits a rounded peak between T c and T O C , and the phase correlation length within the transverse ab plane diverges at T c from above, in a manner consistent with that of a 2D Berezinskii-Kosterlitz-Thouless 4 These authors contributed equally to this work.

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“…The heat capacity of WZ GaN is used in evaluating the scaling factor for TS GaN because changes in heat capacity during the phase transformation are negligible. [18][19][20] Figure 2 shows the thermal conductivity and stress 21 as functions of strain for a nanowire with diameter d = 2.26 nm at T Q = 334 K ͑T MD = 500 K͒. When the strain reaches 0.06, the stress drops precipitously.…”

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confidence: 99%

Strain dependence of thermal conductivity of [0001]-oriented GaN nanowires

Jung

Cho

Zhou

2011

Applied Physics Letters

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The thermomechanical behavior of ͓0001͔-oriented GaN nanowires with 2.26 and 3.55 nm in diameter under tensile loading is analyzed using molecular dynamics simulations with the Green-Kubo method and quantum correction. A phase transformation from wurtzite to a tetragonal structure is observed. The thermal conductivity is found to decrease as the wires undergo tensile deformation and phase transformation, except for the smallest diameter and temperatures above 1495 K at which it remains largely constant as the axial strain increases. The different trends appear to result from phonon behavior changes primarily associated with the surface structures of the nanowires at the different conditions. The coupling between the thermal and mechanical behaviors of nanostructures is important because it provides a mechanism for designing nanoscale devices and for enhancing the performance of devices. The variation with loading or deformation of thermal conductivity of nanowires and nanofilms of a range of materials is of particular interest and has been extensively studied. 1-6 For example, it has been reported that a structural transformation from wurtzite ͑WZ͒ to a graphitelike ͑HX͒ structure in ͓0110͔-oriented ZnO nanowires under tensile loading causes significant changes in the thermal conductivity of the nanowires. 2,7 The dominant effects that cause the conductivity change come from differences in density of the crystalline structures.In related studies, a tetragonal structure ͑TS͒ with fouratom rings is observed in ͓0001͔-oriented ZnO ͑Refs. 8 and 9͒ and GaN ͑Ref. 10͒ nanowires. This structure results from a phase transformation from WZ under uniaxial tensile loading. So far, thermal response changes of the nanowires associated with this structural transform have not been studied. Here, we report the results of molecular dynamics ͑MD͒ calculations that relate to the response changes. The focus is on the thermal conductivity of wires of different sizes at different temperatures. To obtain a more accurate quantification of the conductivity and temperature, the empirical approach of Lee et al. 11 for quantum correction of MD data and temperature is used.In this analysis, GaN nanowires with the WZ structure and a hexagonal cross section like that in Fig. 1 of Ref. 10 are considered. The axis of the nanowires is in the ͓0001͔ crystalline direction. Periodic boundary conditions are specified in the axial direction and the lateral surfaces of the wires are traction-free. The length of the wires is 14.45 nm and the diameters considered are 2.26 and 3.55 nm. The calculations are carried out using the LAMMPS code. 12 The Buckingham potential 13 is used to describe the short range interactions between atoms and the Wolf summation 14,15 is used to evalu-ate the long-range Coulombic forces. This potential reproduces the structural, elastic, and dielectric constants of the WZ, zinc-blende, and rocksalt structures. 13 Native-defect formation and surface relaxation are also effectively predicted. 13 The results obtained by using this p...

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Specific Heat of Superconducting Zn Nanowires

Cited by 18 publications

References 28 publications

Magnetic-field induced quantum-size cascades in superconducting nanowires

Magnetic-field induced quantum-size cascades in superconducting nanowires

Dimensional crossover transition in a system of weakly coupled superconducting nanowires

Strain dependence of thermal conductivity of [0001]-oriented GaN nanowires

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