Superconductivity is an advantageous physical phenomenon observed in some materials, which entails an electrical resistance of zero below specific critical temperatures. This phenomenon is known to arise following the formation of so-called Cooper pairs (i.e., pairs of electrons).
There are two known types of superconductivity, known as conventional and unconventional superconductivity. In conventional superconductors, the formation of Cooper pairs is mediated by the interaction between electrons and phonons (i.e., vibrations in a crystal's lattice), as explained by Bardeen-Cooper-Schrieffer (BCS) theory.
Unconventional superconductors, on the other hand, are materials that exhibit a superconductivity that is not prompted by electron–phonon interactions. While many past studies have tried to shed light on the mechanisms underpinning unconventional superconductivity, its underlying physics remains poorly understood.
Researchers at Massachusetts Institute of Technology (MIT), Harvard University and the National Institute for Materials Science in Japan recently set out to better understand the mechanisms behind the unconventional superconductivity observed in twisted graphene moiré heterostructures, material consisting of stacked graphene sheets twisted at an angle of approximately 1.1°.
Their paper, published in Physical Review Letters, unveils a large and tunable kinetic inductance (i.e., a resistance to changes in current prompted by the inertia of charge carriers) in twisted trilayer graphene, offering new insight about the underpinnings of superconductivity in moiré materials.
"It was quite a moment when Pablo Jarillo-Herrero and his team made public a sensational discovery in 2018," Paritosh Karnatak, co-senior author of the paper, told Phys.org. "They demonstrated that two graphene layers twisted with respect to each other at a particular, small angle showed superconductivity in a certain doping range (number density of charge carriers), and other unexpected, correlated states.
"It was quite a moment when Pablo Jarillo-Herrero and his team made public a sensational discovery in 2018," Paritosh Karnatak, co-senior author of the paper, told Phys.org. "They demonstrated that two graphene layers twisted with respect to each other at a particular, small angle showed superconductivity in a certain doping range (number density of charge carriers), and other unexpected, correlated states.
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