Vladimir Dobrosavljevic, Florida State University, Geometrically Frustrated Coulomb Liquids

Date: Mon. April 8th, 2019, 12:45 pm-1:45 pm

Geometrically Frustrated Coulomb Liquids
V. Dobrosavljevic
Department of Physics and National High Magnetic Field Laboratory
Florida State University, Tallahassee, Florida 32306, USA

We show[1] that introducing long-range Coulomb interactions immediately lifts the massive
ground state degeneracy induced by geometric frustration for electrons on quarter-filled
triangular lattices in the classical limit. Important consequences include the stabilization of
a stripe-ordered crystalline (global) ground state, but also the emergence of very many lowlying
metastable states with amorphous “stripe-glass” spatial structures[2]. Melting of the
stripe order thus leads to a frustrated Coulomb liquid at intermediate temperatures, showing
remarkably slow (viscous) dynamics, with very long relaxation times growing in Arrhenius
fashion upon cooling, as typical of strong glass formers. On shorter time scales, the system
falls out of equilibrium and displays the aging phenomena characteristic of super-cooled
liquids around the glass transition. Our results show remarkable similarity with the recent
observations[3] of charge-glass behavior in ultra-clean triangular organic materials of the θ-
(BEDT-TTF) family. These ideas seem also to be of relevance for very recent discovery[6] of
self-generated glassiness of polarons in transition-metal dichalcogenide 1T-TaS2.

1. S. Mahmoudian, L. Rademaker, A. Ralko, S. Fratini, and V. Dobrosavljević, Phys. Rev. Lett.
115, 025701.
2. J. Schmalian and P. G. Wolynes, Phys. Rev. Lett. 85, 836 (2000).
3. F. Kagawa, T. Sato, K. Miyagawa, K. Kanoda, Y. Tokura, K. Kobayashi, R. Kumai, and Y.
Murakami, Nat. Phys. 9, 422 (2013).
4. N. Ogawa, A. Ueda, H. Mori, M. Kawasaki, and Y. Tokura, Phys. Rev. B 91, 041101 (2015).
5. Y. Gerasimenko, I. Vaskivskyi, J. Ravnik, Jaka Vodeb, V. V. Kabanov, and D. Mihailovic,
preprint, arXiv:1803.00255.

Figure 1: (a) Structure factor C(k) of the frustrated Coulomb liquid obtained for
a L = 36 triangular lattice size and averaged over 1000 independent equilibrated
Monte Carlo runs at T = 0.04V above the melting transition. Clearly defined
dffuse Bragg peaks are observed at the (linear) stripe order M-point, and
symmetry equivalent points. (b) Same, plotted along the high-symmetry lines of
the Brillouin zone drawn in panel (a); (c) A snapshot illustrating a typical “stripe
liquid” configuration.

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