Ph.D. Thesis Colloquium 

 Speaker:                     Sambunath Das 

Topic:                         Quantum phases and magnetization plateaus of skewed spin ladders 

Date & Time:             24th November 2021 at 4:00 PM through Microsoft team 



 Spin ladders are a type of low-dimensional system with a finite number of magnetically connected chains. These ladders are referred to as quasi one-dimensional systems and they serve as a link between one- and two-dimensional systems. Many compounds have been discovered experimentally that have a ladder-like structure [1, 2, 3]. Depending on the different bond structures, the ladders are named as zigzag ladder, 3/4, 3/5, 5/5 and 5/7 skewed ladders [4, 5]. The physical properties of these ladders depend on the geometry, symmetry, and spin at each site in the system. Spin gap, vector chiral phase, spin density wave (SDW) phase and bond order wave (BOW) phase are some of the exotic physical properties present in these systems [5]. 


In this presentation, I’ll talk about our study on the spin-1 model of 5/7, 3/4 and 3/5 skewed ladders, as well as their ground state properties [6,7]. I will also describe our findings about the occurrence of magnetization plateaus in the spin-1/2 model of 3/4, 3/5, 5/5 and 5/7 skewed ladders in the presence of magnetic field [8]. The observed magnetization plateaus in these systems are consistent with the Oshikawa, Yamanaka and Affleck (OYA) condition. Finally, I will conclude by discussing how the entanglement entropy and fidelity calculation help us to understand the quantum phase transitions in the spin-1/2 model of 3/4, 3/5 and 5/7 skewed ladders. 



 1. E. Dagoto, Rep. Prog. Phys. 62 (1999) 1525–1571 

2. Françoise Damay et. al, Phys. Rev. B 81 (2010) 214405 

3. Rafaela A.L. Silva and Manuel Almeida, J. Mater. Chem. C 9 (2021), 10573 

4. S. Thomas, S. Ramasesha, K. Hallberg and D. Garcia, Phys. Rev. B86 (2012), 180403(R). 

5. G. Giri, D. Dey, M. Kumar, S. Ramasesha and Z.G. Soos, Phys. Rev. B 95, (2017), 224408. 

6. S. Das, D. Dey, M. Kumar and S. Ramasesha,Phys. Rev. B 104, (2021), 125138. 

7. S. Das, D. Dey, S. Ramasesha and M. Kumar, J. Appl. Phys.129, (2021), 223902. 

8. D. Dey, S. Das, M. Kumar and S. Ramasesha, Phys. Rev. B 101 (2020), 195110.