고체이론연구실에서 포항공대의 Dheeraj Kumar Singh 박사님을 초청하여 아래와 같이 세미나를 개최합니다.

학과 구성원 여러분의 많은 참석을 부탁드립니다.

○ 일시: 2018년 11월 13일(화) 오전 11:00 ~ 13:00

○ 장소: Creative Learning Room, 7^th Floor in Samsung Library

○ 연사: Dr. Dheeraj Kumar Singh (POSTECH)

○ Title: Hund’s coupling driven role of  $d_{3z^2-r^2}$ in stabilizing the hole-doped antiferromagnetic state in cuprates

○ Abstract:  One of the long-standing theoretical issues in high-$T_c$ cuprates is the instability of the

hole-doped antiferromagnetic state when considered with the one-orbital model, which has been

established through various studies. Cuprates, however, do exhibit a hole-doped antiferromagnetic

state though in a narrow doping regime. We show that such a robust state can be realized within a

recently proposed minimal two-orbital model incorporating Cu $d_{3z^2-r^2}$ orbital. The

stabilization is a direct result of the Hund’s coupling enforcing the d_{x^2-y^2} orbital electronic density 

~ 1 accompanied with a significant reduction of $d_x^2-y^2$ spectral density at the Fermi level. This, in turn,

leads to the suppression of intraband fluctuations detrimental to the antiferromagnetic

phase. The hole doping involves removal of  mainly d_{3z^2-r^2} electrons that are localized

considerably. In other words, the $d_{3z^2-r^2}$ shifts up above the Hubbard split lower

d_{x^2-y^2} band. Thus, in this new scenario, holes can also occupy $d_{3z^2-r^2}$, in addition to the

oxygen $p$ orbital.