HEP-HEN Seminar- “Revisiting Kohn and Luttinger after 60 years: superconductivity from a repulsive interaction and application to quark matter” with Prof. Yuki Fujimoto (RIKEN-Berkeley Center, University of California, Berkeley)
Physics Seminar
March 11, 2025
11:00 AM - 11:00 AM
Location
SES 2214
Calendar
Download iCal FileTitle: Revisiting Kohn and Luttinger after 60 years: superconductivity from a repulsive interaction and application to quark matter
Abstract: We revisit the renormalization group (RG) analysis of the Kohn-Luttinger (KL) mechanism for superconductivity. The KL mechanism induces superconductivity in systems with a repulsive bare interaction. The key factor here is the screening effect, which makes the induced interaction attractive in channels with nonzero angular momentum (l > 0), thus triggering the BCS instability. According to the original argument, the resulting gap is exponentially small, with its exponent scaling as −l^4. In this talk, we present the RG analysis of the KL effect. Our results show that the KL gap exponent is proportional to −l, indicating a significant enhancement of the KL mechanism compared to the previously known results. The KL mechanism was initially formulated within perturbation theory, where the series is known to converge poorly in certain cases—most notably, for the p-wave pairing gap induced by a repulsive s-wave contact interaction. This poor convergence can be attributed to a divergent integrand in a specific class of diagrams that contain both the BCS logarithm and the Kohn anomaly. This suggests that the contributions from the Kohn anomaly must be resummed separately from the BCS logarithm, and RG is capable of resumming such contributions. Finally, we discuss potential applications of our results to the problem of secondary pairing in two-flavor color superconductors and explore the implications for the properties of quark matter inside neutron stars.
Date posted
Feb 19, 2025
Date updated
Feb 19, 2025