Past studies examining MATBG also unveiled the emergence of what is known as a "strange" metal regime in the proximity of the superconducting dome, as well as a significantly enhanced electron-phonon coupling. While these observations were confirmed by later works, the exact mechanisms underpinning them remain unclear.

Researchers at the Barcelona Institute of Science and Technology, the National Institute for Material Sciences, and Massachusetts Institute of Technology (MIT) have recently taken a closer look at these properties of MATBG using a different, low temperature phase diagram than those utilized in previous works. Their paper, published in Nature Physics, gathered new valuable insight about the material's quantum critical behavior.

"Early reports on the electrical transport properties of twisted bilayer graphene revealed two fascinating features: the emergence of a so-called 'strange' metal regime in the vicinity of the superconducting dome and a sharply enhanced electron-phonon coupling," Alexandre Jaoui, one of the researchers who carried out the study, told Phys.org. "Yet, both features share, under certain conditions, a common signature: a linear-in-temperature resistivity. One question that arose was: can a single microscopic mechanism, electrons scattering off phonons, account for both previous observations? Or is this signature, in the low temperature region, pointing to the existence of additional scattering centers affecting charge carriers?"