1. frustrated spin-1/2 lattice models at three-colorable point and flat-band physics

Oleg Derzhko

ICMP NAS, Ukraine

17 November 2021 Wed 5 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

Recently, a special point of the S=1/2 XXZ kagome system has been discovered: For antiferromagnetic transversal interaction and two times smaller ferromagnetic longitudinal interaction the ground state can be mapped onto three-coloring configurations and it has a huge degeneracy scaling as 1.20872...3N/2, where N is the number of the lattice sites [1,2]. Later on, this construction has been extended to other lattices [5] and more general forms of anisotropic interaction [7]. These ground states are of interest for nonequilibrium physics too [3,6].

My talk is based on our recent paper [4]. We consider a one-dimensional S=1/2 XXZ lattice of triangular motif (the sawtooth-chain lattice), which admits a three-coloring representation of the ground-state manifold [1], to illustrate the relation to the flat-band physics [8,9]. In particular, we elaborate the low-temperature thermodynamics in a small magnetic field complementing our analytical findings by exact-diagonalization and finite-temperature Lanczos method calculations. Furthermore, we illustrate the manifestation of the flat-band physics of the anisotropic model under consideration in comparison with two isotropic flat-band Heisenberg sawtooth chains examined earlier.

[1] H.J.Changlani et al., Phys. Rev. Lett. 120, 117202 (2018).

[2] H.J.Changlani et al., Phys. Rev. B 99, 104433 (2019).

[3] K.Lee et al., Phys. Rev. B 101, 241111(R) (2020).

[4] O.Derzhko, J.Schnack, D.V.Dmitriev, V.Ya.Krivnov, and J.Richter, Eur. Phys. J. B 93, 161 (2020).

[5] S.Pal et al., Phys. Rev. B 103, 144414 (2021).

[6] K.Lee, A.Pal, and H.J.Changlani, Phys. Rev. B 103, 235133 (2021).

[7] G.Palle and O.Benton, Phys. Rev. B 103, 214428 (2021).

[8] O.Derzhko et al., Low Temperature Physics 33, 745 (2007).

[9] O.Derzhko, J.Richter, and M.Maksymenko, Int. J. Mod. Phys. B 29, 1530007 (2015).