Flat-band superconductivity in periodically strained graphene: mean-field and Berezinskii–Kosterlitz–Thouless transition

Abstract

In the search of high-temperature superconductivity one option is to focus on increasing the density of electronic states. Here we study both the normal and s-wave superconducting state properties of periodically strained graphene, which exhibits approximate flat bands with a high density of states, with the flatness tunable by the strain profile. We generalize earlier results regarding a one-dimensional harmonic strain to arbitrary periodic strain fields, and further extend the results by calculating the superfluid weight and the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature TBKT to determine the true transition point. By numerically solving the self-consistency equation, we find a strongly inhomogeneous superconducting order parameter, similarly to twisted bilayer graphene. In the flat band regime the order parameter magnitude, critical chemical potential, critical temperature, superfluid weight, and BKT transition temperature are all approximately linear in the interaction strength, which suggests that high-temperature superconductivity might be feasible in this system. We especially show that by using realistic strain strengths TBKT can be made much larger than in twisted bilayer graphene, if using similar interaction strengths. We also calculate properties such as the local density of states that could serve as experimental fingerprints for the presented model. :1910.06671v2 [cond-mat.supr-con] arXiv

The Magnetization of a Composite Based on Reduced Graphene Oxide and Polystyrene

“…According to some theoretical models, T c is predicted to range up to room temperature if the DOS is reconstructed, forming so-called flat bands in graphene [62][63][64][65]. It is supposed that such a DOS reconstruction will occur if graphene, multilayer graphene, or carbon flakes are subjected to mechanical stress [5,22].…”

Interband plasmon polaritons in magnetized charge-neutral graphene

“…Importantly, our calculations show that rather low values of magnetic fields (B < 2 T) are already suitable for the observations. From a different perspective, we believe that our analysis of plasmons in a single-layer magnetized CN graphene can be a tool providing insights into various intriguing quantum phenomena in CNG via optical experiments 12,13,15 . We foresee that the intriguing phenomena recently discovered in the single-layer CN graphene, as for instance the giant intrinsic photoresponse 12 , colossal magneto-optical activity 11 and markedly reduced electronic noise 44 , combined with the ability to support GPPs, make magnetized CN graphene promising for a graphene-based magnetically controllable nanoplasmonic and optoelectronic devices, such as gas sensors or bio-sensors [44][45][46] or magnetically tunable plasmon-assistant photodetectors 47 , among other.…”

“…Interestingly, collective effects in twisted bilayer CNG can enable the formation of GPP associated with the interband transitions 13,14 between the flat electronic bands that appear at the magic angle. Intriguingly, these interband GPP can be closely related with the superconducting states appearing in periodically strained single-layer CNG 15 and magic angle twisted bilayer graphene [16][17][18] . Up to now, although having a high interest for superconducting states formation and increasing of operational frequencies for graphene-based plasmonic devices, GPPs in CNG have been barely explored.…”

Magnetization of Ultraviolet-Reduced Graphene Oxide Flakes in Composites Based on Polystyrene

“…According to some theoretical models, Tc is predicted to range up to room temperature if the DOS is reconstructed, forming so-called flat bands in graphene [48][49][50][51]. It is supposed that such a DOS reconstruction will occur if graphene, multilayer graphene or carbon flakes are subjected to mechanical stress [52][53][54][55]. As mentioned in the introduction, the photoreduction process results in forming numerous submicron holes within the UV- According to the dependence M(H) obtained, polystyrene exhibits ferromagnetic behavior characteristic of the entire investigated temperature range (5-300 K).…”