Tailoring Metal Insulator Transitions $\&$ Band Topology via Off-resonant Periodic Drive in an Interacting Triangular Lattice

TL;DR

This paper explores how off-resonant periodic electromagnetic driving can induce and control metal-insulator transitions and topological phases in an interacting triangular lattice system, revealing tunable band topology and emergent models.

Contribution

It demonstrates that high-frequency driving can engineer topological band structures and stabilize an emergent Kane-Mele model in an interacting lattice, with tunable band gaps and topological transitions.

Findings

Periodic drive induces topological bands with non-zero Chern numbers.

Charge fluctuations are suppressed on the interacting sub-lattice by U but do not open a gap without drive.

External drive enables repeated metal-insulator transitions and band inversions with topological phase changes.

Abstract

A triangular lattice with onsite Coulomb interaction $U$ present only on one sub-lattice, is periodically driven by electromagnetic field with a frequency $\Omega \gg (t,~U)$ at half filling. In this high frequency limit, the electromagnetic vector potential, with an amplitude $A$, modifies the bare hopping and generates new next nearest neighbour hopping parameters. For $U=0$, the driving acts like an emergent intrinsic spin-orbit coupling term and stabilises three dispersive bands with the lower and upper bands having non zero Chern numbers. Within a slave rotor mean field theory, we show that while $U$ freezes out charge fluctuations on the interacting sub-lattice, it does not open up a charge gap without the external drive. In presence of the drive, and small $U$, the system exhibits repeated metal insulator transitions as a function of the amplitude $A$. For large $U$, we establish that the freezing of charge fluctuations on the interacting sub-lattice stabilizes an emergent, low energy \textit{half filled non-interacting Kane-Mele model}, whose band gaps can be tuned by varying $A$. In this limit, we show that the external drive provides an handle to engineer periodic band inversions at specific values of $A$ accompanied by topological phase transitions that are characterised by swapping of band Chern numbers.