The Lax pair for C_2-type Ruijsenaars-Schneider model

We study the C_2 Ruijsenaars-Schneider(RS) model with interaction potential of trigonometric type. The Lax pairs for the model with and without spectral parameter are constructed. Also given are the involutive Hamiltonians for the system. Taking nonrelativistic limit, we obtain the Lax pair of C_2 Calogero-Moser model.Comment: LaTeX2e, 10 pages, some misprints corrected and sections rearrange

Helical damping and anomalous critical non-Hermitian skin effect

Non-Hermitian skin effect and critical skin effect are unique features of non-Hermitian systems. In this Letter, we study an open system with its dynamics of single-particle correlation function effectively dominated by a non-Hermitian damping matrix, which exhibits $\mathbb{Z}_2$ skin effect, and uncover the existence of a novel phenomenon of helical damping. When adding perturbations that break anomalous time reversal symmetry to the system, the critical skin effect occurs, which causes the disappearance of the helical damping in the thermodynamic limit although it can exist in small size systems. We also demonstrate the existence of anomalous critical skin effect when we couple two identical systems with $\mathbb{Z}_2$ skin effect. With the help of non-Bloch band theory, we unveil that the change of generalized Brillouin zone equation is the necessary condition of critical skin effect.Comment: 7+5 pages, 4+5 figure

Quantum Oscillations in Magnetic Field Induced Antiferromagnetic Phase of Underdoped Cuprates : Application to Ortho-II YBa2Cu3O6.5

Magnetic field induced antiferromagnetic phase of the underdoped cuprates is studied within the t-t'-J model. A magnetic field suppresses the pairing amplitude, which in turn may induce antiferromagnetism. We apply our theory to interpret the recently reported quantum oscillations in high magnetic field in ortho-II YBa2Cu3O6.5 and propose that the total hole density abstracted from the oscillation period is reduced by 50% due to the antiferromagnetism.Comment: 5 pages, 3 figure