## Classical and quantum spin dynamics of the honeycomb $\mathrm{\Gamma}$ model

## Abstract

Quantum-to-classical crossover is a fundamental question in dynamics of quantum many-body systems. In frustrated magnets, for example, it is highly nontrivial to describe the crossover from the classical spin liquid with a macroscopically degenerate ground-state manifold to the quantum spin liquid phase with fractionalized excitations. This is an important issue, as we often encounter the demand for a sharp distinction between the classical and quantum spin liquid behaviors in real materials. Here we take the example of the classical spin liquid in a frustrated magnet with novel bond-dependent interactions to investigate the classical dynamics, and critically compare it with quantum dynamics in the same system. In particular, we focus on signatures in the dynamical spin structure factor. Combining Landau-Lifshitz dynamics simulations and the analytical Martin-Siggia-Rose approach, we show that the low-energy spectra are described by relaxational dynamics and highly constrained by the zero mode structure of the underlying degenerate classical manifold. Further, the higher energy spectra can be explained by precessional dynamics. Surprisingly, many of these features can also be seen in the dynamical structure factor in the quantum model studied by finite-temperature exact diagonalization. Here, we discuss the implications of these results and their connection to recent experiments onmore »

- Authors:

- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Univ. of Toronto, Toronto, ON (Canada); The Hebrew Univ., Jerusalem (Israel)
- The Univ. of Tokyo, Tokyo (Japan); JST PRESTO, Tokyo (Japan)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
- Univ. of Toronto, Toronto, ON (Canada); Canadian Institute for Advanced Research, Toronto, ON (Canada); Korea Inst. for Advanced Study, Seoul (Korea)

- Publication Date:

- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1530111

- Alternate Identifier(s):
- OSTI ID: 1460487

- Grant/Contract Number:
- AC05-00OR22725

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physical Review B

- Additional Journal Information:
- Journal Volume: 98; Journal Issue: 4; Journal ID: ISSN 2469-9950

- Publisher:
- American Physical Society (APS)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

### Citation Formats

```
Samarakoon, Anjana M., Wachtel, Gideon, Yamaji, Youhei, Tennant, David Alan, Batista, Cristian D., and Kim, Yong Baek. Classical and quantum spin dynamics of the honeycomb Γ model. United States: N. p., 2018.
Web. doi:10.1103/PhysRevB.98.045121.
```

```
Samarakoon, Anjana M., Wachtel, Gideon, Yamaji, Youhei, Tennant, David Alan, Batista, Cristian D., & Kim, Yong Baek. Classical and quantum spin dynamics of the honeycomb Γ model. United States. doi:10.1103/PhysRevB.98.045121.
```

```
Samarakoon, Anjana M., Wachtel, Gideon, Yamaji, Youhei, Tennant, David Alan, Batista, Cristian D., and Kim, Yong Baek. Sun .
"Classical and quantum spin dynamics of the honeycomb Γ model". United States. doi:10.1103/PhysRevB.98.045121. https://www.osti.gov/servlets/purl/1530111.
```

```
@article{osti_1530111,
```

title = {Classical and quantum spin dynamics of the honeycomb Γ model},

author = {Samarakoon, Anjana M. and Wachtel, Gideon and Yamaji, Youhei and Tennant, David Alan and Batista, Cristian D. and Kim, Yong Baek},

abstractNote = {Quantum-to-classical crossover is a fundamental question in dynamics of quantum many-body systems. In frustrated magnets, for example, it is highly nontrivial to describe the crossover from the classical spin liquid with a macroscopically degenerate ground-state manifold to the quantum spin liquid phase with fractionalized excitations. This is an important issue, as we often encounter the demand for a sharp distinction between the classical and quantum spin liquid behaviors in real materials. Here we take the example of the classical spin liquid in a frustrated magnet with novel bond-dependent interactions to investigate the classical dynamics, and critically compare it with quantum dynamics in the same system. In particular, we focus on signatures in the dynamical spin structure factor. Combining Landau-Lifshitz dynamics simulations and the analytical Martin-Siggia-Rose approach, we show that the low-energy spectra are described by relaxational dynamics and highly constrained by the zero mode structure of the underlying degenerate classical manifold. Further, the higher energy spectra can be explained by precessional dynamics. Surprisingly, many of these features can also be seen in the dynamical structure factor in the quantum model studied by finite-temperature exact diagonalization. Here, we discuss the implications of these results and their connection to recent experiments on frustrated magnets with strong spin-orbit coupling.},

doi = {10.1103/PhysRevB.98.045121},

journal = {Physical Review B},

number = 4,

volume = 98,

place = {United States},

year = {2018},

month = {7}

}

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