Superconductivity and electrical resistivity in alkali metal doped fullerides: Phonon mechanism

Bulletin of materials science

R K Singh⁴  Dinesh Varshney¹  K K Choudhary³  A Dube² 

[1] School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, India$$Department of Physics, Barkatullah University, Bhopal 462 026, India$$School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, IndiaSchool of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, India$$Department of Physics, Barkatullah University, Bhopal 462 026, India$$Department of Physics, Barkatullah University, Bhopal 462 026, IndiaSchool of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, India$$Department of Physics, Barkatullah University, Bhopal 462 026, India$$;School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, India$$School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, IndiaSchool of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452 017, India$$;Department of Physics, SVITS, Indore 453 331, India$$Department of Physics, SVITS, Indore 453 331, IndiaDepartment of Physics, SVITS, Indore 453 331, India$$;Department of Physics, Barkatullah University, Bhopal 462 026, India$$Department of Physics, Barkatullah University, Bhopal 462 026, IndiaDepartment of Physics, Barkatullah University, Bhopal 462 026, India$$

关键词: Fullerenes;    alkali-C60 phonon;    on-ball-C60 phonon;    pressure effect;    electrical resistivity.;   

DOI  :  

学科分类：材料工程

来源: Indian Academy of Sciences

【 摘 要 】

We consider a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. We first study the intercage interactions between the adjacent C₆₀ cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C₆₀ phonons. Electronic parameter as repulsive parameter and the attractive coupling strength are obtained within the random phase approximation. Transition temperature, ð‘�??_c, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C₆₀ phonons as 5 K, which is much lower as compared to reported ð‘�??_c (â‰�? 20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. To illustrate the usefulness of the above approach, the carbon isotope exponent and the pressure effect are also estimated. Temperature dependence of electrical resistivity is then analysed within the same model phonon spectrum. It is inferred from the two-peak model for phonon density of states that high frequency intramolecular phonon modes play a major role in pairing mechanism with possibly some contribution from alkali-C₆₀ phonon to describe most of the superconducting and normal state properties of doped fullerides.

【 授权许可】

Unknown