# Z_2 topological order near the Neel state of the square lattice antiferromagnet

### APA

Sachdev, S. (2017). Z_2 topological order near the Neel state of the square lattice antiferromagnet. Perimeter Institute. https://pirsa.org/17050081

### MLA

Sachdev, Subir. Z_2 topological order near the Neel state of the square lattice antiferromagnet. Perimeter Institute, May. 18, 2017, https://pirsa.org/17050081

### BibTex

@misc{ pirsa_PIRSA:17050081, doi = {10.48660/17050081}, url = {https://pirsa.org/17050081}, author = {Sachdev, Subir}, keywords = {Condensed Matter}, language = {en}, title = {Z_2 topological order near the Neel state of the square lattice antiferromagnet}, publisher = {Perimeter Institute}, year = {2017}, month = {may}, note = {PIRSA:17050081 see, \url{https://pirsa.org}} }

Subir Sachdev Harvard University

## Abstract

We classify quantum states proximate to the semiclassical Neel state of the spin S=1/2 square lattice antiferromagnet with two-spin near-neighbor and four-spin ring exchange interactions. Motivated by a number of recent experiments on the cuprates and the iridates, we examine states with Z_2 topological order, an order which is not present in the semiclassical limit. Some of the states break one or more of reflection, time-reversal, and lattice rotation symmetries, and can account for the observations. We discuss implications for the pseudogap phase.