2015/12/08 by Wei‐Cheng Lee, Wei-Cheng Lee, L. H. Greene +1 · 15 citations
Materials Science · Physics and Astronomy · #Andreev reflection #Condensed matter physics #Conductance #Electron #Iron-based superconductors research #Phonon #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum tunnelling #Rare-earth and actinide compounds #Spectroscopy #Superconductivity #cond-mat.mtrl-sci #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1088/0034-4885/79/9/094502
published in arXiv (Cornell University) 79(9), 094502 (Cornell University) · 25 pages, 8 figures, an invited review for a special issue on strongly correlated electron systems in Rep. Prog. Phys
openalex publication_date 2015/12/08 · arxiv created 2016/05/26 · arxiv updated 2016/08/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We review recent progress in point contact spectroscopy (PCS) to extract spectroscopic information out of correlated electron materials, with the emphasis on non-superconducting states. PCS has been used to detect bosonic excitations in normal metals, where signatures (e.g. phonons) are usually less than 1% of the measured conductance. In the superconducting state, point contact Andreev reflection (PCAR) has been widely used to study properties of the superconducting gap in various superconductors. In the last decade, there have been more and more experimental results suggesting that the point contact conductance could reveal new features associated with the unusual single electron dynamics in non-superconducting states, shedding a new light on exploring the nature of the competing phases in correlated materials. We will summarize the theories for point contact spectroscopy developed from different approaches and highlight these conceptual differences distinguishing point contact spectroscopy from tunneling-based probes. Moreover, we will show how the Schwinger-Kadanoff-Baym-Keldysh (SKBK) formalism together with the appropriate modeling of the nano-scale point contacts randomly distributed across the junction leads to the conclusion that the point contact conductance is proportional to the \it effective density of states, a physical quantity that can be computed if the electron self energy is known. The experimental data on iron based superconductors and heavy fermion compounds will be analyzed in this framework. These recent developments have extended the applicability of point contact spectroscopy to correlated materials, which will help us achieve a deeper understanding of the single electron dynamics in strongly correlated systems.