Novel phases and phase transitions in condensed matter

Nové fázy a fázové prechody v kondenzovaných látkach

Project APVV-15-0496 July 2016 - December 2019

Dept. Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava

Investigators: PhD Students:
Roman Martoňák (PI) Richard Hlubina Peter Markoš Oto Kohulák Lukáš Kopnický Dominika Melicherová Ondrej Toth

Former members
Dušan Plašienka František Herman

  1. D. Melicherová, O. Kohulák, D. Plašienka and R. Martoňák: Structural evolution of amorphous polymeric nitrogen from ab initio molecular dynamics simulations and evolutionary search
  2. J. Hašík, E. Tosatti and R. Martoňák: Quantum and classical ripples in graphene
    Physical Review B 97, 140301(R) (2018), arXiv:1712.08089.
  3. Yu Wang,Shu-Qing Jiang, Alexander F. Goncharov, Federico A. Gorelli, Xiao-Jia Chen, Dušan Plašienka, Roman Martoňák, Erio Tosatti, and Mario Santoro: Synthesis and Raman spectroscopy of a layered SiS2 phase at high pressures
    The Journal of Chemical physics 148, 014503 (2018).
  4. F. Herman and R. Hlubina: Thermodynamic properties of Dynes superconductors
    Physical Review B 97, 014517 (2018), arXiv:1710.03465.
  5. P. Markoš and V. Kuzmiak: Resonant scattering from a two-dimensional honeycomb PT dipole structure
    Physical Review A 97, 053807 (2018), arXiv:1804.09487.
  6. P. Markoš and K. Muttalib: Universality of phonon transport in nanowires dominated by surface roughness
    Physical Review B 97, 085423 (2018), arXiv:1802.03281.

  1. D. Plašienka, R. Martoňák and M. C. Newton: Ab initio molecular dynamics study of the structural and electronic transition in VO2
    Physical Review B 96, 054111 (2017), arXiv:1704.04917.
  2. R. Martoňák, Davide Ceresoli, Tomoko Kagayama, Yusuke Matsuda, Yuh Yamada, and Erio Tosatti: High-pressure phase diagram, structural transitions, and persistent nonmetallicity of BaBiO3: Theory and experiment
    Physical Review Materials 1, 023601 (2017), arXiv:1704.04098.
  3. O. Kohulák and R. Martoňák: New high-pressure phases of MOSe2 and MOTe2
    Physical Review B 95, 054105 (2017), DOI: 10.1103/PhysRevB.95.054105, arXiv:1611.07757.
  4. F. Herman and R. Hlubina: Electromagnetic properties of impure superconductors with pair-breaking processes
    Physical Review B 96, 014509 (2017), arXiv:1705.04674.
  5. F. Herman and R. Hlubina: Consistent two-lifetime model for spectral functions of superconductors,
    Physical Review B 95, 094514 (2017), arXiv:1701.04430.
  6. K. Staliunas, P. Markoš and V. Kuzmiak: Scattering properties of a PT dipole
    Physical Review A 96, 043852 (2017), arXiv:1710.09092.

  1. D. Plašienka, R. Martoňák and E. Tosatti: Creating new layered structures at high pressures: SiS2
    Scientific Reports 6, 37694; doi: 10.1038/srep37694 (2016).

Central problem of condensed matter physics is a theoretical and experimental study of new phases observed in materials, which determine their physical properties. Theoretical description of phases is based on the hypothesis of universality of their properties and transitions from one phase into another: different materials have similar physical properties if they are in the same physical phase. Textbook examples are paramagnetic and ferromagnetic phases and the universal phase transition from one phase to another.

Experimental and technological progress in last decades opens the possibility to prepare new physical phases of matter, normally not present in Nature. One way for experimental search of new phases is to expose material to extreme conditions (high pressure, high magnetic field, high or very low temperature etc). Another possibility is direct synthesis of new structures in laboratory (layered 2D structures, new crystals or amorphous materials with non-standard bonding patterns, compounds with special composition such as high-temperature superconductors, and many others). Very recent example of remarkable progress in this field is the observation of superconductivity at record temperature of 203 K in hydrogen-rich system H 3 S at pressure beyond 100 GPa.

The existence of new physical phase could imply new interesting physical properties of a given material. The search for new phases and detailed analysis of their properties is therefore interesting both for experimental and applied research. Besides this application potential, searching for new phases and description of their physical properties is an extremely challenging theoretical problem which often leads to principal new understanding of various aspects of condensed matter physics. As an example of novel concepts let us mention quasicrystals or several recently discovered novel electronic phases, such as topological insulators or spin liquids.

In this Project we plan to investigate, both analytically and numerically, some phases found recently in condensed matter as well as predict new ones. We focus on problems which correspond to long-time expertise of the team members and divide the project into three aims:

A. Structural phase transitions and search for new phases
B. Pseudogap in high-temperature superconductors
C. Metal-insulator transition in disordered electron systems

An important part of our work consists also of development and generalization of algorithms employed in numerical simulations. In particular, in part A (especially within the aim A1) we plan to improve existing techniques and develop new approaches for dynamical simulations of structural transformations in solids. Within the aim C, programs for simulation of the diffusion of a quantum particle in a random potential and for the analysis of electron transport in various non-standard two- dimensional structures will be developed.