Bulletin of the American Physical Society
Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021; Rutgers University, New Brunswick, New Jersey
Session G01: Quantum Matter: Superconductivity I |
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Chair: Premala Chandra, Rutgers University Room: 201A |
Sunday, December 5, 2021 9:00AM - 9:36AM |
G01.00001: Bond bipolarons and high temperature superconductivity. Invited Speaker: NIkolay Prokof'ev Polarons originating from phonon displacement modulated hopping have relatively light masses and, thus, are of significant current interest as candidates for bipolaron mechanism of high-temperature superconductivity. We observe that the bond model, when the dominant coupling comes from atomic vibrations on lattice bonds, can be solved by efficient sign-free Monte Carlo methods based on the path-integral formulation of the particle sector. We introduce the corresponding algorithms and provide results for singlet bipolarons in two dimensions. Estimates for the superconducting temperature are exceeding predictions based on the Eliashberg theory and suggest that the route towards high transition temperature in the multiparametric space of the model lies between the Scylla of large size of moderately light bipolarons and Charybdis of large mass of compact bipolarons. As a result, on-site repulsion and relatively narrow electronic bands are helping s-wave superconductivity in sharp contrast with existing expectations. [Preview Abstract] |
Sunday, December 5, 2021 9:36AM - 10:12AM |
G01.00002: Electron-Electron Interaction in the Uniform Electron Gas Invited Speaker: Kun Chen We discuss the effective electron-electron interaction of uniform electron gas in a broad temperature regime covering the superconducting phase, Fermi liquid phase, and the warm dense electron gas. We develop a variational diagrammatic Monte Carlo technique to calculate the structure factor and spin susceptibility with high precision. The data allow us to parameterize the exchange-correlation kernel for the electron-electron interaction. We find that the effective interaction leads to exotic superconductivity at a low temperature. Meanwhile, it also causes a universal quantum correction to the structure factor of a warm dense electron gas in the high-temperature limit. [Preview Abstract] |
Sunday, December 5, 2021 10:12AM - 10:48AM |
G01.00003: Structural predictions and lattice dynamics with embedded DMFT approach Invited Speaker: Kristjan Haule Recent solutions of the uniform electron gas problem by variational diagrammatic Monte Carlo method at metallic densities gave us new insights into the screening in solids and show that in metallic solids the short-range interaction point of view is most appropriate for fast convergence towards the exact solution. This gives us a new understanding of why Dynamical Mean Field Theory (DMFT) has been so successful in describing numerous correlated solids. In this talk, I will also explain in greater detail one such implementation, namely the DFT+embedded DMFT functional with its exact double-counting implementation. In the remainder of the talk, I will discuss the feedback effect of incoherent spectra on structural properties of solids and will show how the implementation of forces in this approach allows one to successfully predict structures and lattice dynamics of correlated solids, which will demonstrated on iron superconductor FeSe. [Preview Abstract] |
Sunday, December 5, 2021 10:48AM - 11:00AM Not Participating |
G01.00004: Triplet pairing via Kondo hybridization - applications to UTe$_2$ and CeRh$_2$As$_2$ Tamaghna Hazra, Piers Coleman We explore pairing mechanisms for triplet superconductivity mediated by Kondo interactions, relevant for UTe$_2$ and CeRh$_2$As$_2$. In these systems, the upper critical field violates the Pauli limit by an order of magnitude, and there are multiple distinct superconducting phases which appear to be enhanced and even enabled by strong magnetic fields. Taken together, the experimental puzzles raised by these systems challenge our current understanding of heavy fermion superconductivity and raise the intriguing possibility of a very new kind of superconductivity driven by the local moments of U and Ce. We seek to unify the Kondo physics with the triplet pairing in a coherent framework. With this motivation, we present a mean-field analysis of a simple two-channel Kondo model which has two spins at locally-noncentrosymmetric sites in the unit cell, inspired by UTe$_2$ and CeRh$_2$As$_2$, which illustrates the emergence of local triplet correlations as a result of Kondo hybridization with spin-orbit coupled local moments. In the spirit of a resonating valence bond picture, the superconductivity can be understood as the condensation of spin-triplet pre-formed pairs which are odd under exchange of the two U/Ce sites. [Preview Abstract] |
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