Searching superconductivity in low dimensional materials from conventional to unconventional
일 시 : 2021년 04월 13일 화요일 16:00
연 사 : 김 수 란 교수 (경북대학교 물리교육과)
장 소 : 자연과학관 747호 & 온라인 동시진행 ( https://us02web.zoom.us/j/89235295426 , 줌회의 ID: 892 3529 5426 )
HOST : 김 재 용 교수님
초 록
Superconductivity is one of the most intensively studied subjects in condensed matter physics community. Recent discovery of hydride superconductors shows the importance of the high-pressure route to the synthesis of novel functional materials, which can promote the search for new phases of superconductors. In this talk, I will introduce two low dimensional superconductors. First one is magnesium carbides which we used as a representative example of computational high-pressure studies. We predicted various compositions of Mg-C compounds up to 150 GPa and proposed MgC2 consists of one-dimensional graphene layers and Mg atomic layers. This new phase provides a good platform to study superconductivity of metal intercalated graphene nano-ribbons. Our MgC2 exhibit a strong electron-phonon coupling strength of 0.6 whose corresponding superconductivity transition temperature reached 15 K. As a second part, using machine learning and first principle calculations, we predict the maximum superconducting transition temperature (Tc,max) of unconventional cuprate superconductors and suggest the explicit functional form for Tc,max with R2 of 0.969. We have found that material dependent parameters such as the Bader charge of apical oxygen, the bond strength between apical atoms, and the number of superconducting layers are important features to estimate Tc,max. Furthermore, we predict the Tc,max of hypothetical cuprates generated by replacing apical cations with other elements to search new cuprates. When Ga is an apical cation, the predicted Tc,max is the highest among the hypothetical structures with 71, 117, and 131 K for one, two, and three CuO2 layers, respectively