Research Experiences for Undergraduates in Computational Methods with Applications in Materials Science
MSU Affiliation
College of Arts and Sciences; Department of Physics and Astronomy; Center for Computational Sciences
Major
Physics
Research Mentor
Rudolf T. Clay
Creation Date
7-27-2026
Abstract
The Spin-Peierls (SP) transition is a classic phenomenon in low-dimensional quantum mechanics, wherein strong magnetoelastic coupling drives a structural lattice distortion, opening a spin gap and establishing a dimerized ground state. The SP transition is well understood in quasi-one-dimensional (quasi-1D) materials. In the organic charge- transfer tetramethyltetrathiafulvalene (TMTTF)2X salts, pressure suppresses the SP transition, giving way to antiferromagnetism and then superconductivity. Pressure is expected to increase the two-dimensional character of the material but also to introduce geometric frustration and competing magnetic fluctuations. Our central question is whether these higher-dimensional effects suppress or destroy the SP state in favor of magnetic long-range order. In this work, we test this dimensional crossover by performing extensive Density Matrix Renormalization Group (DMRG) calculations on a two-dimensional (2D) triangular-lattice Peierls-Hubbard model. Using a cylindrical geometry with open boundary conditions along the long axis and periodic boundary conditions along the circumference, we systematically sweep the interchain hopping parameter to move from decoupled 1D chains to a fully interacting 2D limit. To map the phase diagram and identify the transition from an SP state to an Antiferromagnetic (AFM) phase, the simulations measure electronic bond order and phonon displacement modulation amplitudes as primary SP order parameters, alongside the AFM diagnostic spin structure factor and charge structure factors. This numerical framework probes the survival threshold of magnetoelastic dimerization against competing magnetic orders in higher dimensions.
Presentation Date
Summer 7-30-2026
Keywords
computational physics, spin-Peierls, electron-phonon coupling
Recommended Citation
Fotedar, Medha A. and Clay, Rudolf T., "Dimensional Crossover and Suppression of the Spin-Peierls State" (2026). Research Experiences for Undergraduates in Computational Methods with Applications in Materials Science. 27.
https://scholarsjunction.msstate.edu/ccs-reu/27
