0000000000129131

AUTHOR

V. J. Kauppila

showing 3 related works from this author

Collective amplitude mode fluctuations in a flat band superconductor

2015

We study the fluctuations of the amplitude (i.e. the Higgs-Anderson) mode in a superconducting system of coupled Dirac particles proposed as a model for possible surface or interface superconductivity in rhombohedral graphite. We show that the absence of Fermi energy and vanishing of the excitation gap of the collective amplitude mode in the model leads to a large fluctuation contribution to thermodynamic quantities such as the heat capacity. As a consequence, the mean-field theory becomes inaccurate indicating that the interactions lead to a strongly correlated state. We also present a microscopic derivation of the Ginzburg-Landau theory corresponding to this model.

Superconductivity (cond-mat.supr-con)Condensed Matter - SuperconductivityFOS: Physical sciences
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Flat-band superconductivity in strained Dirac materials

2016

We consider superconducting properties of a two-dimensional Dirac material such as graphene under strain that produces a flat band spectrum in the normal state. We show that in the superconducting state, such a model results in a highly increased critical temperature compared to the case without the strain, inhomogenous order parameter with two-peak shaped local density of states and yet a large and almost uniform and isotropic supercurrent. This model could be realized in strained graphene or ultracold atom systems and could be responsible for unusually strong superconductivity observed in some graphite interfaces and certain IV-VI semiconductor heterostructures.

superconducting propertiesMaterials sciencesuprajohtavuusDirac (software)FOS: Physical sciences02 engineering and technology01 natural scienceslaw.inventionsuprajohteetSuperconductivity (cond-mat.supr-con)Condensed Matter::Materials SciencelawUltracold atompuolijohteetCondensed Matter::Superconductivity0103 physical sciencesgrafeeniGraphite010306 general physicsSuperconductivityLocal density of statesCondensed matter physicsta114Dirac materialsGrapheneCondensed Matter - SuperconductivityIsotropySupercurrent021001 nanoscience & nanotechnology0210 nano-technologyPhysical Review B
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Collective amplitude mode fluctuations in a flat band superconductor formed at a semimetal surface

2016

We study the fluctuations of the amplitude (i.e., the Higgs-Anderson) mode in a superconducting system of coupled Dirac particles proposed as a model for possible surface or interface superconductivity in rhombohedral graphite. This system also serves as a generic model of a topological semimetal with an interaction-driven transition on its surface. We show that the absence of Fermi energy and vanishing of the excitation gap of the collective amplitude mode in the model leads to a large fluctuation contribution to thermodynamic quantities, such as the heat capacity. As a consequence, the mean-field theory becomes inaccurate, indicating that the interactions lead to a strongly correlated sta…

SuperconductivityPhysicsSurface (mathematics)ta114Condensed matter physicsDirac (software)Fermi energyamplitude mode01 natural sciencesHeat capacitysemimetalsSemimetal010305 fluids & plasmasROOM-TEMPERATUREAmplitude0103 physical sciences010306 general physicsphysicsExcitationPhysical Review B
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