연구처

전자구조론 및 양자물성 연구실

Electronic structure theory and computational quantum materials laboratory

전자구조론 및 양자물성 연구실에서는 빛과 물질과의 상호작용을 기본적인 양자역학의 원리로부터 계산해 내는 것에 세계적인 전문성을 가지고 있다. 구체적으로 실시간 밀도범함수론에 전자기장을 추가해서 섭동론을 벗어나는 강한 상호작용계를 계산해내는 선도적인 계산연구 수단을 발전시켜 왔으며, 이를 이용하여 분자계, 금속계, 위상부도체계 등 다양한 물성과 빛의 상호작용을 규명해 왔다. 물성물리학 분야의 중요 관심은 전기장에 견인된 전하-스 핀-포논의 동적 거동을 제일 원리적으로 계산해 내는 것인데, 위상부도체 등에서 시간반전 대칭성이 동역학적으로 어떤 변환을 겪는가를 real-time TDDFT 동역학 계산법에 외부장(빛)을 벡터 포텐셜 형태로 넣어서 실시간(time-dependent)으로 계산하는 것에 있다. 이에 대한 방법론 발전과 정은 JCTC (2016)에 발표하였으며, 그것을 위상 부도체의 전류문제에 적용한 것이, PNAS (2019) 에 요약되어 있다. 같은 방법을 고체물리계의 “포논에 의한 시간반전대칭성 붕괴 문제”와 “포논에 의한 전자구조 베류곡률 변화”에 적용한 연구가 Nature Communications (2018, 2019)에 각각 발표되었다. 이 연구들에서 전하전류, 스핀전류, 전하의 광전류를 real-time TDDFT로 계산하고 그것으로부터 Chern insulator 또는 Quantum Spin-Hall insulator의 홀전도도 및 스핀홀 전도도를 계산할 수 있다는 것을 보였다.
Our laboratory’s main theme is the first-principles quantum mechanical calculations of light-matter interactions or full ab initio description of materials’ quantum states under a strong or weak light field. To materialize this vision, we have worked on the electron-correlation part of the time-dependent density functional theory(DFT) and explored the limitation and capability of DFT-based methods.
Since Schrödinger’s and Dirac’s formulation of quantum mechanics at around the late 1920s, diverse branches of theories have developed to deal with quantum mechanics of condensed matters in a way as ab initio as possible. The relativistic or non-relativistic Hamiltonian consists of two-body interactions of every pair of many bodies, which gives rise to enormous complexity in the ab initio treatment. One of the most common approaches is the density functional theory(DFT), in which an effective one-body Hamiltonian is solved self-consistently, and various hierarchical treatments have been introduced to overcome the limitations of such an effective one-body theory. While these methods have been remarkably successful for the ground state or the excited state within the linear response regime, the ab initio description for the non-linear regime of the excited state has remained challenging. On the other hand, the experimental side’s community is rapidly growing toward non-equilibrium or transient phenomena, mainly through the femtosecond pump and probe techniques. Such measurements include perturbations, such as photons or electrons colliding with a condensed matter, and the transient phenomena at the boundary of static phases of multiferroic structures.

Our laboratory’s main theme is the first-principles quantum mechanical calculations of light-matter interactions or full ab initio description of materials’ quantum states under a strong or weak light field. To materialize this vision, we have worked on the electron-correlation part of the time-dependent density functional theory(DFT) and explored the limitation and capability of DFT-based methods.
Since Schrödinger’s and Dirac’s formulation of quantum mechanics at around the late 1920s, diverse branches of theories have developed to deal with quantum mechanics of condensed matters in a way as ab initio as possible. The relativistic or non-relativistic Hamiltonian consists of two-body interactions of every pair of many bodies, which gives rise to enormous complexity in the ab initio treatment. One of the most common approaches is the density functional theory(DFT), in which an effective one-body Hamiltonian is solved self-consistently, and various hierarchical treatments have been introduced to overcome the limitations of such an effective one-body theory. While these methods have been remarkably successful for the ground state or the excited state within the linear response regime, the ab initio description for the non-linear regime of the excited state has remained challenging. On the other hand, the experimental side’s community is rapidly growing toward non-equilibrium or transient phenomena, mainly through the femtosecond pump and probe techniques. Such measurements include perturbations, such as photons or electrons colliding with a condensed matter, and the transient phenomena at the boundary of static phases of multiferroic structures.