Kosterlitz-Thouless melting of magnetic order in the triangular quantum Ising material TmMgGaO4

Abstract

Frustrated magnets hold the promise of material realizations of exotic phases of quantum matter, but direct comparisons of unbiased model calculations with experimental measurements remain very challenging. Here we design and implement a protocol of employing many-body computation methodologies for accurate model calculations-of both equilibrium and dynamical properties-for a frustrated rare-earth magnet TmMgGaO 4 (TMGO), which explains the corresponding experimental findings. Our results confirm TMGO is an ideal realization of triangular-lattice Ising model with an intrinsic transverse field. The magnetic order of TMGO is predicted to melt through two successive Kosterlitz-Thouless (KT) phase transitions, with a floating KT phase in between. The dynamical spectra calculated suggest remnant images of a vanishing magnetic stripe order that represent vortex-antivortex pairs, resembling rotons in a superfluid helium film. TMGO therefore constitutes a rare quantum magnet for realizing KT physics, and we further propose experimental detection of its intriguing properties.

Intrinsic quantum Ising model on a triangular lattice magnet TmMgGaO4

“…Their results supported the validity of the TFIM for TmMgGaO 4 . Reference [67] suggested the system first enters the BKT phase at ∼4K and then enters the three-sublattice ordered state at ∼1 K. This differs from the results of the current work, where we have ∼1K for the upper BKT transition and ∼0.5 K for the lower one. They further established the roton mode at the M point inside the three-sublattice ordered state.…”

“…We mention a couple recent works on TmMgGaO 4 and the TFIM on triangular lattice. A recent numerical-oriented work [67] explored our proposed effective model for TmMgGaO 4 using more updated numerical techniques and focused on the numerical aspects of the model. Their results supported the validity of the TFIM for TmMgGaO 4 .…”

Universal thermodynamics in the Kitaev fractional liquid

“…In this work we employ the exponential tensor renormalization group (XTRG) [34][35][36][37] at finite temperature to explore the extended Kitaev model with additional Heisenberg and interactions, which denies QMC simulations. We perform accurate thermodynamic calculations down to very low temperature and find an emergent Curie law of magnetic susceptibility below a high-T scale T H (and above the low-T scale T L ), due to the fluctuating gauge fluxes and the predominant bond-directional nearest-neighbor (NN) spin correlations.…”

Evidence for complex fixed points in pandemic data

“…Depending on the underlying mechanism behind the loss of conformality, one can envision several scenarios ranging from a Berezinski-Kosterlitz-Thouless (BKT)-like phase transition, first discovered in two dimensions [21] and later proposed for four dimensions in [22][23][24][25][26][27][28], to a jumping (non-continuous) phase transition [29]. Evidence for the BKT transition has been found in various two-dimensional materials and physical systems [30][31][32][33]. A large body of numeric and analytic work has followed the discovery that one can achieve (near) conformal dynamics in four dimensions with small number of matter fields [34].…”