Presentation Information
[PC1-05-INV]Investigation of Superconductivity in Carrier-Doped Cuprates via Ab Initio Low-Energy Effective Hamiltonians
*Ryui Kaneko1 (1. Sophia University (Japan))
Keywords:
cuprates,ab initio Hamiltonian,variational Monte Carlo method
Since the discovery of high-temperature superconductors in copper oxides (cuprates) in 1986, they have been keeping the record for the highest critical temperatures at ambient pressure. Over the years, considerable progress has been made both experimentally and theoretically. However, the microscopic origins that govern the diverse material dependencies, such as the wide range of optimal critical temperatures, ranging from 10 K to 130 K, remain one of the major open issues in condensed matter physics. One reason for this difficulty is that the cuprate superconductors belong to a class of strongly correlated electron systems, where the effects of Coulomb repulsion between electrons are substantial. Consequently, it is essential to solve complex many-body problems arising from these strong interactions in a manner that accurately takes into account materials dependence.
To challenge this, we began with ab initio single-layer low-energy effective Hamiltonians for a number of cuprates, derived from first-principles calculations without any adjustable parameters [1]. We have conducted large-scale computations using state-of-the-art quantum many-body calculation methods incorporated with machine learning techniques to clarify the ground-state properties of these Hamiltonians [2]. We have successfully reproduced experimental observations of the similarities and differences among four cuprate compounds. Furthermore, we have identified the key factors that control the strength of superconductivity and proposed a formula that predicts the optimal superconducting transition temperatures. This formula has shown to be applicable across all four materials that we studied.
We also focus on the dependence of the superconducting transition temperature Tc on the number of layers and applied pressure. In the trilayer cuprate HgBa2Ca2Cu3O8+delta (Hg1223), which exhibits the highest Tc among cuprates, Tc reaches approximately 138K at ambient pressure and around 164K under pressure. Clarifying the microscopic origin and mechanism behind this high Tc is meaningful for achieving even higher Tc. We report computational results obtained by applying the many-variable variational Monte Carlo method to the effective Hamiltonian [3] already derived for Hg1223. Because of the difference in carrier concentration between the outer and inner layers of the trilayer system, self-doping occurs between them, affecting the emergence of superconductivity.
The present work has been achieved in collaboration with Michael T. Schmid, Jean B. Moree, Youhei Yamaji, and Masatoshi Imada.
[1] J. B. Moree, M. Hirayama, M. T. Schmid, Y. Yamaji, and M. Imada, Phys. Rev. B 106, 235150 (2022).
[2] M. T. Schmid, J. B. Moree, R. Kaneko, Y. Yamaji, and M. Imada, Phys. Rev. X 13, 041036 (2023).
[3] J. B. Moree, Y. Yamaji, and M. Imada, Phys. Rev. Research 6, 023163 (2024).
To challenge this, we began with ab initio single-layer low-energy effective Hamiltonians for a number of cuprates, derived from first-principles calculations without any adjustable parameters [1]. We have conducted large-scale computations using state-of-the-art quantum many-body calculation methods incorporated with machine learning techniques to clarify the ground-state properties of these Hamiltonians [2]. We have successfully reproduced experimental observations of the similarities and differences among four cuprate compounds. Furthermore, we have identified the key factors that control the strength of superconductivity and proposed a formula that predicts the optimal superconducting transition temperatures. This formula has shown to be applicable across all four materials that we studied.
We also focus on the dependence of the superconducting transition temperature Tc on the number of layers and applied pressure. In the trilayer cuprate HgBa2Ca2Cu3O8+delta (Hg1223), which exhibits the highest Tc among cuprates, Tc reaches approximately 138K at ambient pressure and around 164K under pressure. Clarifying the microscopic origin and mechanism behind this high Tc is meaningful for achieving even higher Tc. We report computational results obtained by applying the many-variable variational Monte Carlo method to the effective Hamiltonian [3] already derived for Hg1223. Because of the difference in carrier concentration between the outer and inner layers of the trilayer system, self-doping occurs between them, affecting the emergence of superconductivity.
The present work has been achieved in collaboration with Michael T. Schmid, Jean B. Moree, Youhei Yamaji, and Masatoshi Imada.
[1] J. B. Moree, M. Hirayama, M. T. Schmid, Y. Yamaji, and M. Imada, Phys. Rev. B 106, 235150 (2022).
[2] M. T. Schmid, J. B. Moree, R. Kaneko, Y. Yamaji, and M. Imada, Phys. Rev. X 13, 041036 (2023).
[3] J. B. Moree, Y. Yamaji, and M. Imada, Phys. Rev. Research 6, 023163 (2024).