Two-channel point-contact tunneling theory of superconductors

Abstract

We introduce a two-channel tunneling model to generalize the widely used BTK theory of point-contact conductance between a normal metal contact and superconductor. Tunneling of electrons can occur via localized surface states or directly, resulting in a Fano resonance in the differential conductance $G=dI/dV$. We present an analysis of $G$ within the two-channel model when applied to soft point-contacts between normal metallic silver particles and prototypical heavy-fermion superconductors CeCoIn${}_5$ and CeRhIn${}_5$ at high pressures. In the normal state the Fano line shape of the measured $G$ is well described by a model with two tunneling channels and a large temperature-independent background conductance. In the superconducting state a strongly suppressed Andreev reflection signal is explained by the presence of the background conductance. We report Andreev signal in CeCoIn${}_5$ consistent with standard $d_{x^2-y^2}$-wave pairing, assuming an equal mixture of tunneling into [100] and [110] crystallographic interfaces. Whereas in CeRhIn${}_5$ at 1.8 and 2.0 GPa the signal is described by a $d_{x^2-y^2}$-wave gap with reduced nodal region, i.e., increased slope of the gap opening on the Fermi surface. A possibility is that the shape of the high-pressure Andreev signal is affected by the proximity of a line of quantum critical points that extends from 1.75 to 2.3 GPa, which is not accounted for in our description of the heavy-fermion superconductor.

arXiv comment13 pages, 13 figures

References in corpus (45)

• "Deconfined" quantum critical points
• Locally critical quantum phase transitions in strongly correlated metals
• Quantum criticality
• How do Fermi liquids get heavy and die?
• Hidden Magnetism and Quantum Criticality in the Heavy Fermion Superconductor CeRhIn5
• Unconventional superconductivity in CeIrIn${}_5$ and CeCoIn${}_5$: Specific heat and thermal conductivity studies
• Imaging the Fano Lattice to 'Hidden Order' Transition in URu2Si2
• Probing multiband superconductivity by point-contact spectroscopy
• Visualizing heavy fermions emerging in a quantum critical Kondo lattice
• Imaging Cooper Pairing of Heavy Fermions in CeCoIn5
• Superconducting Gap Structure of Spin-Triplet Superconductor Sr_2RuO_4 Studied by Thermal Conductivity
• Visualizing Nodal Heavy Fermion Superconductivity in CeCoIn5
• Visualizing the Formation of the Kondo Lattice and the Hidden Order in URu2Si2
• Local fluctuations in quantum critical metals
• Sign reversal of field-angle resolved heat capacity oscillations in a heavy fermion superconductor CeCoIn${}_5$ and $d_{x^2-y^2}$ pairing symmetry
• Andreev Reflection in Heavy-Fermion Superconductors and Order Parameter Symmetry in CeCoIn_5
• Electron Cotunneling into a Kondo Lattice
• The Fermi surface of CeCoIn5: dHvA
• Field-angle Dependence of the Zero-Energy Density of States in the Unconventional Heavy-Fermion Superconductor CeCoIn5
• Pressure-induced anomalous magnetism and unconventional superconductivity in CeRhIn5 : 115In-NQR Study under Pressure
• Differential Conductance and Quantum Interference in Kondo Systems
• Magnetic structure of CeRhIn_5 as a function of pressure and temperature
• Coexistence of Antiferromagnetism and Superconductivity near the Quantum Criticality in Heavy Fermion Compound CeRhIn${}_5$
• Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn_5
• Theory of Asymmetric Tunneling in the cuprate superconductors
• Specific Heat of CeRhIn5: Pressure-Driven Evolution of the Ground State from Antiferromagnetism to Superconductivity
• Observation of the hybridization gap and Fano resonance in the Kondo lattice URu2Si2
• Kondo Destruction and Quantum Criticality in Kondo Lattice Systems
• Point-Contact Spectroscopy of the Heavy-Fermion Superconductor CeCoIn${}_5$
• Tunneling into clean Heavy Fermion Compounds: Origin of the Fano Lineshape
• Electronic Duality in Strongly Correlated Matter
• Calculated de Haas-van Alphen quantities of Ce(M)In5 (M=Co, Rh, and Ir) compounds
• Probing the nodal gap in the pressure-induced heavy fermion superconductor CeRhIn5
• Kondo destruction and valence fluctuations in an Anderson model
• Quantum waveguide theory of Andreev reflection in multiband superconductors: the case of Fe-pnictides
• The Fano effect in the point contact spectroscopy of heavy electron materials
• Point-contact spectroscopy in heavy-fermion superconductors
• Andreev reflection and order parameter symmetry in heavy-fermion superconductors: the case of CeCoIn${}_5$
• Hidden Order Transition in URu2Si2 and the Emergence of a Coherent Kondo Lattice
• Pressure-Tuned Point-Contact Spectroscopy of URu2Si2 from Hidden Order to Antiferromagnetic States: Similarity of the Fermi Surface Gapping
• Field-angle-resolved anisotropy in superconducting CeCoIn5 using realistic Fermi surfaces
• Exploring of point-contact spectra of Ba1-xNaxFe2As2 in the normal and superconducting state
• Towards a Microscopic Theory for Metallic Heavy-Fermion Point Contacts
• Conductance asymmetry in point-contacts on epitaxial thin films of Ba(Fe${}_{0.92}$Co${}_{0.08}$)${}_2$As${}_2$
• Electron transmission in normal/heavy-fermion superconductor junctions

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