Abstract-Non-perturbative terahertz high-harmonic generation in the three-dimensional Dirac semimetal Cd3As2

Sergey Kovalev, Renato M. A. Dantas, Semyon Germanskiy, Jan-Christoph Deinert, Bertram Green, Igor Ilyakov, Nilesh Awari, Min Chen, Mohammed Bawatna, Jiwei Ling, Faxian Xiu, Paul H. M. van Loosdrecht, Piotr Surówka, Takashi Oka,  Zhe Wang, 

https://www.nature.com/articles/s41467-020-16133-8

Harmonic generation is a general characteristic of driven nonlinear systems, and serves as an efficient tool for investigating the fundamental principles that govern the ultrafast nonlinear dynamics. Here, we report on terahertz-field driven high-harmonic generation in the three-dimensional Dirac semimetal Cd3As2 at room temperature. Excited by linearly-polarized multi-cycle terahertz pulses, the third-, fifth-, and seventh-order harmonic generation is very efficient and detected via time-resolved spectroscopic techniques. The observed harmonic radiation is further studied as a function of pump-pulse fluence. Their fluence dependence is found to deviate evidently from the expected power-law dependence in the perturbative regime. The observed highly non-perturbative behavior is reproduced based on our analysis of the intraband kinetics of the terahertz-field driven nonequilibrium state using the Boltzmann transport theory. Our results indicate that the driven nonlinear kinetics of the Dirac electrons plays the central role for the observed highly nonlinear response.

Abstract-Terahertz field control of in-plane orbital order in La0.5Sr1.5MnO4

• Timothy A Miller,
• Ravindra W Chhajlany,
• Luca Tagliacozzo,
• Bertram Green,
• Sergey Kovalev,
• Dharmalingam Prabhakaran,
• Maciej Lewenstein,
• Michael Gensch
• & Simon Wall

http://www.nature.com/ncomms/2015/150918/ncomms9175/full/ncomms9175.html

Nature Communications

 

6,

 

Article number:

 

8175

 

doi:10.1038/ncomms9175

Received

 

02 February 2015 

Accepted

 

27 July 2015 

Published

 

18 September 2015

In-plane anisotropic ground states are ubiquitous in correlated solids such as pnictides, cuprates and manganites. They can arise from doping Mott insulators and compete with phases such as superconductivity; however, their origins are debated. Strong coupling between lattice, charge, orbital and spin degrees of freedom results in simultaneous ordering of multiple parameters, masking the mechanism that drives the transition. Here we demonstrate that the orbital domains in a manganite can be oriented by the polarization of a pulsed THz light field. Through the application of a Hubbard model, we show that domain control can be achieved by enhancing the local Coulomb interactions, which drive domain reorientation. Our results highlight the key role played by the Coulomb interaction in the control and manipulation of orbital order in the manganites and demonstrate a new way to use THz to understand and manipulate anisotropic phases in a potentially broad range of correlated materials.