Conferences & Schools2017 Arnold Sommerfeld School: Numerical methods for correlated manybody systems
Participant, 11/09/2017  15/09/2017 Venue: Arnold Sommerfeld Center for Theoretical Physics, LMU, Munich, Germany Lecturers (and preliminary topics):  Philippe Corboz (Amsterdam): Projected entangled pair states (PEPS) (introduction)  Olivier Parcollet (Saclay): Dynamical Mean Field Theory (DMFT) & impurity solvers  Lode Pollet (LMU): Quantum Monte Carlo methods  Ulrich Schollwöck (LMU): Matrix product states (MPS), Density matrix renormalization group (DMRG)  Norbert Schuch (MPQ): PEPS (mathematical aspects)  Andreas Weichselbaum (LMU): Numerical renormalization group (NRG)  Steve White (UC Irvine): DMRG in two dimensions The 35th International Symposium on Lattice Field Theory (Lattice 2017)
Participant, 18/06/2017  24/06/2017 Venue: Palacio de Congresos de Granada, Granada, Spain Poster: Chargedensitywave phases of onedimensional model with longrange repulsive interactions M. Szyniszewski Abstract: The onedimensional extended tV model on a lattice describes fermions with repulsive interactions of finite range and exhibits a quantum phase transition between a Luttinger liquid conducting phase and a Mott insulating phase. Its properties make it useful in the description of candidate materials for Mott transistor devices. It is known that by tailoring the potential energy of the insulating system, one can force a phase transition into a different insulating phase [1, 2]. We show how to construct all possible chargedensitywave phases of the system at low critical densities in the atomic limit. Higher critical densities are investigated by a bruteforce analysis of the possible finite unit cells of the Fock states. We present example phase diagrams of the system. We construct a matrix product operator representation of the Hamiltonian of the tV model. Using the matrix product states (MPS) approach we go beyond the atomic limit, where the phase diagrams are much richer. MPS method is especially problematic near the transition between two different chargedensitywave phases and we show how the bond dimension must be increased in order to converge the results. Our results indicate that the number of possible insulating phases grows with both the maximum interaction range and the fermion density and may cause the loss of insulating properties of the material at finite temperatures.
International Conference on Strongly Correlated Electron Systems 2017
Participant, 16/07/2017  21/07/2017 Venue: Clarion Congress Hotel Prague, Prague, Czech Republic Poster: Chargedensitywave phases of a onedimensional model with longrange repulsive interactions M. Szyniszewski N8 HPC Network Event  New approaches to atomistic / quantum simulation of materials
Speaker, 06/01/2017 Venue: The Bar Convent, York, UK Talk: Effects of strain in graphene/hexagonalboronnitride heterostructures M. Szyniszewski, E. Mostaani, N.D. Drummond, V.I. Fal'ko The 34th International Symposium on Lattice Field Theory (Lattice 2016)
Participant, 24/07/2016  30/07/2016 Venue: University of Southampton, Southampton, UK Poster: Fermions with longrange interactions using a matrixproductstates approach M. Szyniszewski Abstract: The longrange tV model of fermions on a lattice is known to exhibit a transition between a Luttinger liquid phase and a Mott insulator phase [1]. At insulating densities, one can tailor the potential energy of the model in such a way that one forces a quantum phase transition to either another insulating chargedensitywave phase, a bondorder phase or a Luttinger liquid [2]. We show how to construct a matrix product operator representation of the Hamiltonian of the tV model and we present phase diagrams calculated using the matrixproductstates approach [3]. We compare these phase diagrams with results obtained in the atomic limit.
NoWNano Summer Conference 2016
Speaker, 27/06/2016  30/06/2016 Venue: Cranage Hall, Cheshire, UK Talk: Diffusion Monte Carlo study of charge carrier complexes in twodimensional semiconductors M. Szyniszewski, E. Mostaani, C. Price, R. Maezono, N. Drummond, V. Fal'ko N8 HPC Network Event  New approaches to atomistic / quantum simulation of materials
Speaker, 08/01/2016 Venue: The Bar Convent, York, UK Talk: Diffusion Monte Carlo study of charge carrier complexes in twodimensional semiconductors M. Szyniszewski, E. Mostaani, C. Price, R. Maezono, N. Drummond, V. Fal'ko Psik 2015 Conference
Speaker, 06/09/2015  11/09/2015 Venue: Kursaal Event Centre, San Sebastian / Donostia, Spain Talk: Diffusion Monte Carlo study of charge carrier complexes in twodimensional semiconductors M. Szyniszewski, E. Mostaani, N. Drummond, V. Fal'ko Abstract: We use a novel description of the interaction between charges in twodimensional (2D) semiconductors to investigate the binding properties of two, three and fourparticle complexes of charge carriers (excitons, trions and biexcitons). We report binding energies and pair distribution functions calculated using diffusion quantum Monte Carlo methods, which are exact for these systems. Our results will enable the interpretation of experimental photoabsorption and photoluminescence measurements on 2D transitionmetal dichalcogenide materials. We show that our data are consistent with previous bindingenergy data for the limits in which the interactions between charges reduce to logarithmic and Coulomb (1/r) forms. We find that the logarithmic interaction that has previously been used to study excitons and trions in 2D semiconductors provides an inadequate description of the behaviour of systems such as molybdenum disulphide, and we provide accurate bindingenergy data for excitons, trions and biexcitons in these materials. Grant: IOP Research Student Conference Fund awarded by IOP Computational Physics Group; Psik Conference Financial Support. The 33rd International Symposium on Lattice Field Theory (Lattice 2015)
Participant, 13/07/2015  18/07/2015 Venue: Kobe International Conference Center, Kobe, Japan Poster: Strong coupling expansion of the tV model (further results) M. Szyniszewski, E. Burovski Abstract: We employ a strong coupling expansion  similar to the one used in the lattice field theory studies [1]  to solve the onedimensional extended tV model of fermions on a lattice [2]. This model is solved for a range of filling factors, including both commensurate  where a charge density wave is present  and incommensurate densities. The first set consists not only of a trivial case of half filling. The method allows us to trace the transition from a Luttinger liquid phase to a Mott insulating phase and calculate the critical parameter K. This simple yet powerful method is not based on Bethe ansatz and it works for both integrable and nonintegrable systems. Furthermore, we investigate how tailoring the interaction can introduce other ordered phases of the system [3].
Tensor Network Summer School 2015
Participant, 01/06/2015  05/06/2015 Venue: Ghent University, Ghent, Belgium Topics:  matrix product states (MPS)  projected entangled pair states (PEPS)  multiscale entanglement renormalization ansatz (MERA) Travel grant: Lancaster University Graduate School Travel Grant GSTG1576. International Conference on Strongly Correlated Electron Systems 2014
Participant, 07/07/2014  11/07/2014 Venue: Campus Saint Martin d'Hères, Grenoble, France Poster: Generalised tV model in one dimension M. Szyniszewski, E. Burovski Abstract: We use a strong coupling expansion [1] to solve the onedimensional extended t‑V model of fermions [2,3]. The model is solved for a range of densities, including both commensurate – where a charge density wave is present – and incommensurate densities. The first set consists not only of a trivial case of half filling. The method allows us to trace the transition from a Luttinger liquid phase to a Mott insulating phase. This simple yet powerful method is not based on Bethe ansatz and it works for both integrable and nonintegrable systems.
Travel grant: Lancaster University Graduate School Travel Grant GSTG1426.
The 32nd International Symposium on Lattice Field Theory (Lattice 2014)
Speaker, 22/06/2014  28/06/2014 Venue: Columbia University, New York, US Talk: Lattice Hamiltonian approach to the Schwinger model K. Cichy, A. KujawaCichy, M. Szyniszewski Abstract: We employ exact diagonalization with strong coupling expansion to the massless and massive Schwinger model. For the massless case, this allows us for a high accuracy continuum limit estimation of the ground state energy and scalar and vector mass gaps with precisions of the order of one part per billion or better. Furthermore, we investigate the chiral condensate and compare our calculations to previous results available in the literature. Oscillations of the chiral condensate which are present while increasing the expansion order are also studied and are shown to be directly linked to the presence of flux loops in the system.

Outreach EventsBritish Science Week
Organiser, 18/03/2015 Sackville Street Building, University of Manchester Science Spectacular
Organiser, 25/10/2014 Whitworth Hall / Museum, University of Manchester
National Science and Engineering Week
Organiser, 21/03/2014 Sackville Street Building, University of Manchester Meet the Nanoscientist
Organiser, 09/02/2013 
© Marcin Szyniszewski 20122015