Condensed Matter seminars

From exciton condensates to organic superconductors - advances through large-scale numerics

by Adrian Kantian (Nordita)

112:028 (Nordita South) ()

112:028 (Nordita South)

Correlated systems of low-dimensional electrons are of particular relevance to both condensed matter theory as well as to applied physics when pairing of fermionic states yields collective bosonic behaviour. Bilayer exciton condensates are one example of this, of special interest as a low-power replacement for the transistor. The organic superconductors (Bechgaard and Fabre salts), which are key systems to understand how pairing between electrons can arise from purely repulsive interactions, are another. Each of these phenomena comes with unique challenges that are very difficult to address through analytical pproaches alone. For bilayer excitons, how to achieve nesting and avoid the screening effects inherent in the conventional 2D proposals quickly leads to the necessity to evaluate the performance of equivalent 1D bilayers quantitatively. In the organics, the hurdles to understand the fundamental mechanism behind unconventional superconductivity are as steep as for the 2D Hubbard model of the cuprates. The density matrix renormalization group (DMRG) has in recent years been parallelized for supercomputers. In this talk, I will show how this powerful numerical technique not only allows to demonstrate how 1D bilayer xcitons could outperform earlier 2D proposals, but also how it enables making a strong case for the existence of superconductivity in the minimal U-V model of the organics from an unbiased, ab-initio approach.