Photomolecular High-Temperature Superconductivity

Abstract

The properties of organic conductors are often tuned by the application of chemical or external pressure, which change orbital overlaps and electronic bandwidths while leaving the molecular building blocks virtually unperturbed. Here, we show that, unlike any other method, light can be used to manipulate the local electronic properties at the molecular sites, giving rise to new emergent properties. Targeted molecular excitations in the charge-transfer salt κ-ðBEDTÀTTFÞ 2 Cu½NðCNÞ 2 Br induce a colossal increase in carrier mobility and the opening of a superconducting optical gap. Both features track the density of quasiparticles of the equilibrium metal and can be observed up to a characteristic coherence temperature T Ã ≃ 50 K, far higher than the equilibrium transition temperature T C ¼ 12.5 K. Notably, the large optical gap achieved by photoexcitation is not observed in the equilibrium superconductor, pointing to a light-induced state that is different from that obtained by cooling. First-principles calculations and model Hamiltonian dynamics predict a transient state with long-range pairing correlations, providing a possible physical scenario for photomolecular superconductivity.

Evidence for metastable photo-induced superconductivity in K3C60

“…on-equilibrium orders in complex materials include photo-induced ferroelectricity 1,2 , magnetic polarization in antiferromagnets 3 and transient superconductivity in the normal state of cuprates and organic conductors [4][5][6][7][8][9] . Among these, much work has been dedicated to alkali-doped fullerides of the A 3 C 60 family ( Fig.…”

Analytical solution for the steady states of the driven Hubbard model

“…Moreover, in a quantum materials setting, a recent experiment has shown how laser excitation of the vibrational modes of the organic charge transfer salt κ − (BEDT − TTF) 2 Cu[N(CN) 2 ]Br, whose conducting layers can be described by a triangular Hubbard model, leads to the formation of transient superconducting features [11]. Density functional theory modeling of the material has shown that the laser excitation induces a periodic time dependence in the parameters of the triangular Hubbard Hamiltonian which, in combination with the irregular geometry of the system, leads to the system transiently establishing particle-hole order as it absorbs energy from the driving field [51].…”

“…Coherent driving has established itself as a fundamental tool for controlling and manipulating the states of quantum systems, from implementing high fidelity gates in few-qubit systems [1] to inducing phase transitions in many-body optical lattices [2]. Within this paradigm, recent experiments have observed how intense laser pulses in the midinfrared regime can transiently induce superconducting features-such as the opening of a gap in the real part of the optical conductivity and vanishing resistivity-when driving various solid state materials out of equilibrium [3][4][5][6][7][8][9][10][11].…”

Parametric resonance of Josephson plasma waves: A theory for optically amplified interlayer superconductivity in YBa2Cu3O6+x

“…Photoinduced superconductivity has been one of the most surprising discoveries of pump and probe experiments in solids. By now it has been observed in three different classes of materials: high-T c cuprates [1][2][3][4][5][6][7], the buckyball superconductor K 3 C 60 [8], and organic superconductors such as (BEDT-TTF) 2 Cu[N(CN) 2 ]Br [9]. In many of these materials, superconductivity has been induced by tuning the pump pulse to be resonant with one of the infrared (IR) active phonon modes; thus, interaction between the strongly excited phonon modes and the many-body electron system is at the heart of this phenomenon.…”