# Optical control of competing exchange interactions and coherent spin-charge coupling in two-orbital Mott insulators

### Submission summary

 As Contributors: Marion Barbeau Arxiv Link: https://arxiv.org/abs/1803.03796v2 Date accepted: 2019-02-21 Date submitted: 2019-02-04 Submitted by: Barbeau, Marion Submitted to: SciPost Physics Domain(s): Theoretical Subject area: Condensed Matter Physics - Theory

### Abstract

In order to have a better understanding of ultrafast electrical control of exchange interactions in multi-orbital systems, we study a two-orbital Hubbard model at half filling under the action of a time-periodic electric field. Using suitable projection operators and a generalized time-dependent canonical transformation, we derive an effective Hamiltonian which describes two different regimes. First, for a wide range of non-resonant frequencies, we find a change of the bilinear Heisenberg exchange $J_{\textrm{ex}}$ that is analogous to the single-orbital case. Moreover we demonstrate that also the additional biquadratic exchange interaction $B_{\textrm{ex}}$ can be enhanced, reduced and even change sign depending on the electric field. Second, for special driving frequencies, we demonstrate a novel spin-charge coupling phenomenon enabling coherent transfer between spin and charge degrees of freedom of doubly ionized states. These results are confirmed by an exact time-evolution of the full two-orbital Mott-Hubbard Hamiltonian.

### Ontology / Topics

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We thank the referees for their comments and suggestions which helped to further improve the manuscript. We provide a detailed explanation on list of changes in the designated section below.

### List of changes

Following the remarks from the referees, we expanded the analysis of the biquadratic exchange interaction and we added of a new figure 3b. Moreover, Figure 2 has been modified in order to better illustrate the different canonical transformations used to derive the exchange interactions. In addition, to make the physics emerging from our work more clear, we added a short discussion on the possible phases that could emerge from the ground state of the effective spin model under driving. In passing through this analysis we unfortunately found a systematic error in signs of the off-diagonal elements of the Hamiltonian matrix, which we have corrected. Therefore, all figures have been recalculated. Importantly, while this leads to small quantitative differences, all qualitative conclusions remain the same.

### Submission & Refereeing History

Resubmission 1803.03796v2 on 4 February 2019
Submission 1803.03796v1 on 13 March 2018

## Reports on this Submission

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### Report

The paper quality improved, small gaps in the exposition were filled, and figures -- improved. The authors also reflected in satisfactory manner all my questions in the new version of the manuscript.

I recommend publication without further delay.

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