Theory of Point Contact Spectroscopy in Correlated Materials

Abstract

We develop a microscopic theory for the point-contact conductance between a metalic electrode and a strongly correlated material using the non-equilibrium Schwinger-Kadanoff-Baym-Keldysh formalism. We explicitly show that in the classical limit, contact size shorter than the scattering length of the system, the microscopic model can be reduced to an effective model with transfer matrix elements that conserve in-plane momentum. We find that the conductance $dI/dV$ is proportional to the {\it effective density of states}, that is, the integrated single-particle spectral function $A(\omega =eV)$ over the whole Brillouin zone. From this conclusion, we are able to establish the conditions under which a non-Fermi liquid metal exhibits a zero-bias peak in the conductance. This finding is discussed in the context of recent point-contact spectroscopy on the iron pnictides and chalcogenides which has exhibited a zero-bias conductance peak.

8 pages, 3 figures, submitted to PNAS, some typos are fixed

References in corpus (7)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Iron pnictides as a new setting for quantum criticality
• Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
• Andreev Reflection in Heavy-Fermion Superconductors and Order Parameter Symmetry in CeCoIn_5
• Electron Cotunneling into a Kondo Lattice
• Point-contact spectroscopy in heavy-fermion superconductors
• Non-Fermi Liquid behavior at the Orbital Ordering Quantum Critical Point in the Two-Orbital Model

Cited by in corpus (4)

• Enhanced superconductivity at the interface of W/Sr${}_2$RuO${}_4$ point contact
• Direct observation of ballistic Andreev reflection
• Automated fabrication technique of gold tips for use in point-contact spectroscopy
• Superconductivity-Induced Changes in Density-Density Correlation Function Enabled by Umklapp Processes