# Dr. Myrta Gruening

## Lecturer in Applied Mathematics and Theoretical Physics

DBB.01.010
+44 (0) 28 9097 6054
m.gruening@qub.ac.uk

Atomistic Simulation Centre School of Mathematics and Physics Queen's University Belfast University Road Belfast BT7 1NN Northern Ireland

### Degrees, Awards and Honours

• 2003 | Ph.D. Physical Sciences - Vrij Universiteit Amsterdam

### Interests

• Development of electronic structure methods and codes
• Electronic structure simulations of electronic and optical properties in bulk and nanostructures

### Most Recent Publications

1. Second harmonic generation in h-BN and MoS2 monolayers: Role of electron-hole interaction, Physical Review B (Rapid), 2014, 89, pp. 081102
doi: 10.1103/PhysRevB.89.081102 Abstract
We study second-harmonic generation in h-BN and MoS$_2$ monolayers using a novel \emph{ab initio} approach based on Many-body theory. We show that electron-hole interaction doubles the signal intensity at the excitonic resonances with respect to the contribution from independent electronic transitions. This implies that electron-hole interaction is essential to describe second-harmonic generation in those materials. We argue that this finding is general for nonlinear optical properties in nanostructures and that the present methodology is the key to disclose these effects.

2. Erratum: Second harmonic generation in h-BN and MoS2 monolayers: Role of electron-hole interactionhttp://dx.doi.org/10.1103/PhysRevB.89.081102, Physical Review B, 2014, 90, No. 19, pp. 199901
doi: 10.1103/PhysRevB.90.199901 Abstract

3. Nonlinear optics from an ab initio approach by means of the dynamical Berry phase: Application to second- and third-harmonic generation in semiconductorshttp://dx.doi.org/10.1103/PhysRevB.90.199901, Physical Review B, 2013, 88, No. 23, pp. 235113
doi: 10.1103/PhysRevB.88.235113 Abstract
We present an ab initio real-time-based computational approach to study nonlinear optical properties in condensed matter systems that is especially suitable for crystalline solids and periodic nanostructures. The equations of motion and the coupling of the electrons with the external electric field are derived from the Berry-phase formulation of the dynamical polarization [Souza et al., Phys. Rev. B 69, 085106 (2004)]. Many-body effects are introduced by adding single-particle operators to the independent-particle Hamiltonian. We add a Hartree operator to account for crystal local effects and a scissor operator to correct the independent particle band structure for quasiparticle effects. We also discuss the possibility of accurately treating excitonic effects by adding a screened Hartree-Fock self-energy operator. The approach is validated by calculating the second-harmonic generation of SiC and AlAs bulk semiconductors: an excellent agreement is obtained with existing ab initio calculations from response theory in frequency domain [Luppi et al., Phys. Rev. B 82, 235201 (2010)]. We finally show applications to the second-harmonic generation of CdTe and the third-harmonic generation of Si.