Superconducting state parameters of La100-C GaC binary metallic glasses

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Aditya Vora
Keyword(s):  
Experimental Data ◽  
Local Field ◽  
Metallic Glasses ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Correction Function ◽  
Phonon Coupling ◽  
Local Field Correction ◽  
Electron Phonon Coupling ◽  
Coulomb Pseudopotential

AbstractThe theoretical investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T C, isotope effect exponent α and effective interaction strength N O V of six binary La100-C GaC (C = 16, 20, 22, 24, 26 and 28 at. %) metallic glasses have been reported using Ashcroft’s empty core (EMC) model potential for the first time. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. It is observed that the electron-phonon coupling strength λ and the transition temperature T C are quite sensitive to the selection of the local field correction functions, whereas the Coulomb pseudopotential μ*, isotope effect exponent α and effective interaction strength N O V show weak dependences on the local field correction functions. The T C obtained from H-local field correction function are found in qualitative agreement with available experimental data and show almost linear nature with the concentration (C) of ‘Ga’ element. A linear T C equation is proposed by fitting the present outcomes for H-local field correction function, which is in conformity with other results for the experimental data. Also, the present results are found to be in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the metallic glasses.

Superconducting state parameters of binary metallic glasses

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Aditya Vora
Keyword(s):  
Local Field ◽  
Metallic Glasses ◽  
Superconducting State ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Model Potential ◽  
Correction Function ◽  
Superconducting State Parameters ◽  
Local Field Correction ◽  
Binary Metallic Glasses

AbstractAshcroft’s empty core (EMC) model potential is used to study the superconducting state parameters (SSPs) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T C, isotope effect exponent αand effective interaction strength N O V of some binary metallic glasses based on the superconducting (S), conditional superconducting (S’) and non-superconducting (NS) elements of the periodic table. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used for the first time with EMC potential in the present investigation to study the screening influence on the aforesaid properties. The T C obtained from the H-local field correction function are in excellent agreement with available theoretical or experimental data. In the present computation, the use of the pseudo-alloy-atom model (PAA) was proposed and found successful. Present work results are in qualitative agreement with such earlier reported experimental values which confirm the superconducting phase in all metallic glasses. A strong dependency of the SSPs of the metallic glasses on the valence ‘Z’ is identified.

Volume dependence of superconducting state parameters of bismuth-based binary alloys: A pseudopotential approach

2019 ◽  
Vol 33 (32) ◽  
pp. 1950394
Author(s):  
Hiral Patel ◽  
Priyank Kumar ◽  
N. K. Bhatt ◽  
P. R. Vyas ◽  
V. B. Gohel
Keyword(s):  
Transition Temperature ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Grüneisen Parameter ◽  
Phonon Coupling ◽  
Gruneisen Parameter ◽  
Volume Dependence ◽  
Electron Phonon Coupling ◽  
Strength Formula ◽  
Coulomb Pseudopotential

A comprehensive and systematic study of superconducting state parameters (SSPs) of Bi-based binary alloys of the form [Formula: see text] has been carried out in the framework of pseudopotential theory at different concentrations ([Formula: see text]) of impurity atom-[Formula: see text] in host atom Bi which varies from 0 to 1. Impurity atom [Formula: see text] has been replaced by In, Tl, Sb and Pb to form four alloy systems. The density-based local form of the pseudopotential proposed by Fiolhais et al. has been used in this study to compute SSPs such as electron–phonon coupling strength ([Formula: see text]), Coulomb pseudopotential ([Formula: see text]), transition temperature ([Formula: see text]), effective interaction strength ([Formula: see text] and isotopic effect parameter ([Formula: see text]) of Bi-based binary alloy systems. Computed results of SSPs of alloys under study are in good agreement with available experimental and other theoretical results. In order to investigate the effect of pressure on SSPs of alloys under study, a theoretical calculation of SSPs as a function of compressed volume is reported. The volume dependence of Debye temperature has been accounted by using Debye–Gruneisen model which involves the Gruneisen parameter. Thus, to describe the effect of pressure on SSPs accurately, the value of Gruneisen parameter should be as accurate as possible. But reported results of Gruneisen parameter in the literature are highly scattered. Due to this reason, we have used two sets of Gruneisen parameter obtained by different methods to understand its role in the computation of SSPs as a function of compressed volume. Further, critical volumes for all alloys at different concentration have been predicted at which electron–phonon coupling strength and Coulomb pseudopotential are equal ([Formula: see text]). At critical volume, superconductivity quenches where transition temperature, [Formula: see text], and effective interaction strength, [Formula: see text], become zero. It is observed that critical volumes predicted by all approaches used in this study are in excellent agreement with each other.

scholarly journals STUDY OF SUPERCONDUCTING EFFECTS IN TRANSITION METALS BASED BINARY ALLOYS USING PSEUDOPOTENTIAL THEORY

2011 ◽  
Vol 48 (1) ◽  
pp. 42-54 ◽  
Author(s):  
Aditya M. Vora
Keyword(s):  
Transition Metals ◽  
Effective Interaction ◽  
Binary Alloys ◽  
Interaction Strength ◽  
Phonon Coupling ◽  
Pseudopotential Theory ◽  
Electron Phonon Coupling ◽  
Potential Formalism ◽  
First Time ◽  
Coulomb Pseudopotential

STUDY OF SUPERCONDUCTING EFFECTS IN TRANSITION METALS BASED BINARY ALLOYS USING PSEUDOPOTENTIAL THEORYSuperconducting state parameters (SSP) (viz., electron-phonon coupling strength λ, Coulomb pseudopotentialμ*transition temperatureTC, isotope effect exponent α and effective interaction strengthNOV) of transition metals based binary alloys are studied using - for the first time - a potential formalism with a pseudoatom-alloy model. In the study, noticeable influence of various exchange and correlation functions on λ andμ*has been revealed. The SSP results are found to be in a qualitative agreement with the available experimental data.

STUDY OF SUPERCONDUCTING STATE PARAMETERS OF TRANSITION METALS BINARY ALLOYS BY A PSEUDOPOTENTIAL APPROACH

2009 ◽  
Vol 23 (02) ◽  
pp. 217-227 ◽  
Author(s):  
ADITYA M. VORA
Keyword(s):  
Superconducting State ◽  
Effective Interaction ◽  
Binary Alloys ◽  
Interaction Strength ◽  
Model Potential ◽  
Superconducting State Parameters ◽  
Local Field Correction ◽  
Electron Phonon Coupling ◽  
Pseudopotential Approach ◽  
Coulomb Pseudopotential

In the present article, we have reported the theoretical study of the superconducting state parameters (SSP) viz. electron–phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent α and effective interaction strength N0V of a 3d-transition metal-based binary alloys using Ashcroft's empty core (EMC) model potential. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. A considerable influence of various exchange and correlation functions on λ and μ* is found from the present study. The present results of the SSP are found in qualitative agreement with the available experimental data wherever they exist.

PSEUDOPOTENTIAL IN THE STUDY OF SUPERCONDUCTING STATE PARAMETERS OF METALLIC GLASSES

2004 ◽  
Vol 18 (12n13) ◽  
pp. 573-582 ◽  
Author(s):  
P. N. GAJJAR ◽  
A. M. VORA ◽  
A. R. JANI
Keyword(s):  
Metallic Glasses ◽  
Superconducting State ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Model Potential ◽  
Superconducting State Parameters ◽  
Proposed Model ◽  
Vegard’S Law ◽  
Electron Phonon Coupling ◽  
Alloy Atom

A recently proposed model potential is used to study the superconducting state parameters viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent α and effective interaction strength NOV of 40 metallic glasses of simple, non-simple as well as transition metals. The advanced screening function due to Sarkar et al. has been employed to include the exchange and correlation effects. Instead of Vegard's law, the use of pseudo-alloy-atom model in the investigation of superconducting state properties of metallic glasses is proposed and found successfully.

Study of superconducting state parameters of amorphous metals by a pseudopotential theory

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Aditya Vora
Keyword(s):  
Superconducting State ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Amorphous Metals ◽  
Pseudopotential Theory ◽  
Superconducting State Parameters ◽  
Local Field Correction ◽  
Electron Phonon Coupling ◽  
First Time ◽  
Exchange And Correlation

AbstractThe theoretical computation of the superconducting state parameters (SSP) viz; electron-phonon coupling strength λ, Coulomb pseudopotential μ *, transition temperature T c, isotope effect exponent α and effective interaction strength N O V of some monovalent (Cu and Au), divalent (Ca, Sr, Ba, αHg, βHg and Ra) and polyvalent (Lu, Rh, Sc, Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Ac, Th, Hf, Ru, Os, Ir, V, Ta, Pa, Cr, Mo, U, Re, Np and Pu) amorphous metals based on the different groups of the periodic table have been carried out for the first time using the well known Ashcroft’s empty core (EMC) model pseudopotential. Herein, we have employed five different types of local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) to study the exchange and correlation effects on the present investigations. A very strong influence of all the exchange and correlation functions have been observed in the present study. Our results are in fair agreement with documented theoretical as well as experimental data. A strong dependency of the SSP of amorphous metals on the valency Z was found.

PRESSURE EFFECTS ON Mg70Zn30 SUPERCONDUCTOR

2009 ◽  
Vol 23 (11) ◽  
pp. 1443-1455 ◽  
Author(s):  
ADITYA M. VORA
Keyword(s):  
Pressure Dependence ◽  
Effective Interaction ◽  
Interaction Strength ◽  
Model Potential ◽  
Pressure Effects ◽  
Local Field Correction ◽  
Electron Phonon Coupling ◽  
Potential Formalism ◽  
Model Pseudopotential ◽  
Linear Nature

Theoretical computation of the pressure dependence of superconducting state parameters of binary Mg 70 Zn 30 is reported using model potential formalism. Explicit expressions have been derived for the volume dependence of the electron–phonon coupling strength λ and the Coulomb pseudopotential μ* considering the variation of Fermi momentum kF and Debye temperature θD with volume. The well-known Ashcroft's empty core (EMC) model pseudopotential and five different types of the local field correction functions viz. Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) have been used for obtaining pressure dependence of transition temperature TC and the logarithmic volume derivative Φ of the effective interaction strength N0V for metallic glass. It has been observed that the μ* curve shows a linear nature and an elbow is formed in the Φ graph.

Electron-Phonon Coupling in Superconducting Alkali-Metal Doped Fullerenes

1992 ◽  
Vol 270 ◽  
Author(s):  
R.A. Jishi ◽  
M.S. Dresseliiaus
Keyword(s):  
Experimental Data ◽  
Alkali Metal ◽  
Phonon Mode ◽  
Coupling Parameter ◽  
Tight Binding ◽  
Superconducting Transition ◽  
Phonon Coupling ◽  
Doped Fullerenes ◽  
Electron Phonon Coupling ◽  
Metal Doped

ABSTRACTThe dimensionless electron-phonon coupling parameter in alkali metal-doped fullerenes isevaluated in a model whereby the electrons are treated within a tight binding formalism.The phonon mode frequencies and eigenvectors are obtained from a lattice dynamical modelwhich accurately fits all available experimental data on these modes. It is shown that the electrormphonon interaction can account for the relatively high values of the superconducting transition temperatures in alkali-metal fullerenes.

Experimental Determination of the Relationship Between Thermal Boundary Resistance and Non-Abrupt Interfaces and Electron-Phonon Coupling

Volume 4 ◽  
2004 ◽  
Author(s):  
Robert J. Stevens ◽  
Pamela M. Norris ◽  
Arthur W. Lichtenberger
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Room Temperature ◽  
Energy Transport ◽  
Boundary Resistance ◽  
Thermal Boundary Resistance ◽  
Phonon Coupling ◽  
Thermal Boundary Conductance ◽  
Electron Phonon Coupling ◽  
The Impact

Understanding thermal boundary resistance (TBR) is becoming increasingly important for the thermal management of micro and optoelectronic devices. The current understanding of room temperature TBR is often not adequate for the thermal design of tomorrow’s complex micro and nano devices. Theories have been developed to explain the resistance to energy transport by phonons across interfaces. The acoustic mismatch model (AMM) [1, 2], which has had success at explaining low temperature TBR, does not account for the high frequency phonons and imperfect interfaces of real devices at room temperature. The diffuse mismatch model (DMM) was developed to account for real surfaces with higher energy phonons [3, 4]. DMM assumes that all phonons incident on the interface from both sides are elastically scattered and then emitted to either side of the interface. The probability that a phonon is emitted to a particular side is proportional to the phonon density of states of the two interface materials. Inherent to the DMM is that the transport is independent of the interface structure itself and is only dependent on the properties of the two materials. Recent works have shown that the DMM does not adequately capture all the energy transport mechanisms at the interface [5, 6]. In particular, the DMM under-predicts transport across interfaces between non Debye-like materials, such at Pb and diamond, by approximately an order of magnitude. The DMM also tends to over-predict transport for interfaces made with materials of similar acoustic properties, Debye-like materials. There have been several explanations and models developed to explain the discrepancies between the mismatch models and experimental data. Some of these models are based on modification of the AMM and DMM [7–9]. Other works have utilized lattice-dynamical modeling to calculate phonon transmission coefficients and thermal boundary conductivities for abrupt and disordered interfaces [3, 6, 10–13]. Recent efforts to better understand room temperature TBR have utilized molecular dynamics simulations to account for more realistic anharmonic materials and inelastic scattering [14–18]. Models have also been developed to account for electron-phonon scattering and its effect on the thermal boundary conductance for interfaces with one metal side [19–22]. Although there have been numerous thermal boundary resistance theoretical developments since the introduction of the AMM, there still is not an unifying theory that has been well validated for high temperature solid-solid interfaces. Most of the models attempt to explain some of the experimental outliers, such as Pb/diamond and TiN/MgO interfaces [6, 23], but have not been fully tested for a range of experimental data. Part of the problem lies in the fact that very little reliable data is available, especially data that is systematically taken to validate a particular model. To this end, preliminary measurements of TBR are being made on a series of metal on non-metal substrate interfaces using a non-destructive optical technique, transient thermal reflectance (TTR) described in Stevens et al. [5]. Initial testing examines the impact of different substrate preparation and deposition conditions on TBR for Debye-like interfaces for which TBR should be small for clean and abrupt interfaces. Variables considered include sputter etching power and duration, electron beam source clean, and substrate temperature control. The impact of alloying and non-abrupt interfaces on the TBR is examined by fabricating interfaces of both Debye-like and non Debye-like interfaces followed by systematically measuring TBR and altering the interfaces by annealing the samples to increase the diffusion depths at the interfaces. Inelastic electron scattering at the interface has been proposed by Hubermann et al. and Sergeev to decrease TBR at interfaces [19–21]. Two sets of samples are prepared to examine the electron-phonon connection to improved thermal boundary conductance. The first consists of thin Pt and Ag films on Si and sapphire substrates. Pt and Ag electron-phonon coupling factors are 60 and 3.1×1016 W/m3K respectively. Both Pt and Ag have similar Debye temperatures, so electron scattering rates can be examined without much change in acoustic effects. The second electron scattering sample series consist of multiple interfaces fabricated with Ni, Ge, and Si to separate the phonon and electron portions of thermal transport. The experimental data is compared to several of the proposed theories.

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