Phys.org December 5, 2024 Although this high Tc is thought to be associated with electron–phonon coupling (EPC), the microscopic coupling mechanism and its role in the superconductivity remain elusive. An international team of researchers (USA – UC Irvine, Princeton University, China, Sweden) atomically resolved the phonons at the FeSe/STO interface and uncovered new optical phonon modes, coupling strongly with electrons, in the energy range of 75–99 meV. These modes were characterized by out-of-plane vibrations of oxygen atoms in the interfacial double-TiOx layer and the apical oxygens in STO. Their results demonstrated that the EPC strength and superconducting gap of 1 uc FeSe/STO […]
Tag Archives: Electron-phonon coupling
High-temperature superconductivity: Exploring quadratic electron-phonon coupling
Phys.org June 20, 2024 When the electron-phonon coupling is quadratic in the phonon coordinates, electrons can pair to form bipolarons due to phonon zero-point fluctuations. A team of researchers in the US (Harvard University, Connecticut University, MIT) studied superconductivity originating from this pairing mechanism in a minimal model and revealed that, in the strong coupling regime, the critical temperature () was only mildly suppressed by the coupling strength, in stark contrast to the exponential suppression in linearly coupled systems, thus implied higher optimal values. They demonstrated that large coupling constants of this flavor were achieved in known materials such as […]
What did the electron ‘say’ to the phonon in the graphene sandwich?
Phys.org February 12, 2024 Understanding electron-phonon interactions is fundamentally important and has crucial implications for device applications. However, in twisted bilayer graphene near the magic angle, this understanding is currently lacking. An international team of researchers (Spain, Japan, USA – MIT, Germany) studied electron-phonon coupling using time- and frequency-resolved photovoltage measurements as direct and complementary probes of phonon-mediated hot-electron cooling. They found a remarkable speedup in cooling of twisted bilayer graphene near the magic angle: the cooling time was a few picoseconds from room temperature down to 5 kelvin, whereas in pristine bilayer graphene, cooling to phonons becomes much slower […]
Thanks to trapped electrons, a material expected to be a conducting metal remains an insulator
Nanowerk July 13, 2023 Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. La1.67Sr0.33NiO4 (LSNO) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. The stripes become dynamic at high temperatures, but LSNO remains insulating presumably because an interplay between magnetic correlations and electron–phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, […]