# Quantum critical scaling at a Bose-glass/superfluid transition: Theory and experiment for a model quantum magnet

## Abstract

Here, we investigate the quantum phase transition from magnetic Bose Glass to magnetic Bose-Einstein condensation induced by a magnetic field in NiCl _{2}∙4SC(NH _{2}) _{2} (dichloro-tetrakis-thiourea-nickel, or DTN), doped with Br (Br-DTN) or site diluted. Quantum Monte Carlo simulations for the quantum phase transition of the model Hamiltonian for Br-DTN, as well as for site-diluted DTN, are consistent with conventional scaling at the quantum critical point and with a critical exponent $z$ verifying the prediction $z = d$; moreover the correlation length exponent is found to be $ν = 0.75(10)$, and the order parameter exponent to be $β = 0.95(10)$. We investigate the low-temperature thermodynamics at the quantum critical field of Br-DTN both numerically and experimentally, and extract the power-law behavior of the magnetization and of the specific heat. Our results for the exponents of the power laws, as well as previous results for the scaling of the critical temperature to magnetic ordering with the applied field, are incompatible with the conventional crossover-scaling ** Ansatz** proposed by Fisher

**[Phys. Rev. B 40, 546 (1989)]. However they can all be reconciled within a phenomenological**

*et al.***in the presence of a dangerously irrelevant operator.**

*Ansatz*- Authors:

- Rice Univ., Houston, TX (United States). Dept. of Physics & Astronomy
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); National Inst. for Materials Physics, Bucharest-Magurele (Romania)
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Univ. of Sao Paulo (Brazil). Inst. of Physics
- Univ. de Lyon, Lyon (France). Ecole Normale Supérieure de Lyon, Lab. de Physique

- Publication Date:

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

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1565036

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Physical Review. B, Condensed Matter and Materials Physics

- Additional Journal Information:
- Journal Volume: 86; Journal Issue: 13; Journal ID: ISSN 1098-0121

- Publisher:
- American Physical Society (APS)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; materials science; physics

### Citation Formats

```
Yu, Rong, Miclea, Corneliu F., Weickert, Franziska, Movshovich, Roman, Paduan-Filho, Armando, Zapf, Vivien S., and Roscilde, Tommaso. Quantum critical scaling at a Bose-glass/superfluid transition: Theory and experiment for a model quantum magnet. United States: N. p., 2012.
Web. doi:10.1103/physrevb.86.134421.
```

```
Yu, Rong, Miclea, Corneliu F., Weickert, Franziska, Movshovich, Roman, Paduan-Filho, Armando, Zapf, Vivien S., & Roscilde, Tommaso. Quantum critical scaling at a Bose-glass/superfluid transition: Theory and experiment for a model quantum magnet. United States. doi:10.1103/physrevb.86.134421.
```

```
Yu, Rong, Miclea, Corneliu F., Weickert, Franziska, Movshovich, Roman, Paduan-Filho, Armando, Zapf, Vivien S., and Roscilde, Tommaso. Tue .
"Quantum critical scaling at a Bose-glass/superfluid transition: Theory and experiment for a model quantum magnet". United States. doi:10.1103/physrevb.86.134421. https://www.osti.gov/servlets/purl/1565036.
```

```
@article{osti_1565036,
```

title = {Quantum critical scaling at a Bose-glass/superfluid transition: Theory and experiment for a model quantum magnet},

author = {Yu, Rong and Miclea, Corneliu F. and Weickert, Franziska and Movshovich, Roman and Paduan-Filho, Armando and Zapf, Vivien S. and Roscilde, Tommaso},

abstractNote = {Here, we investigate the quantum phase transition from magnetic Bose Glass to magnetic Bose-Einstein condensation induced by a magnetic field in NiCl2∙4SC(NH2)2 (dichloro-tetrakis-thiourea-nickel, or DTN), doped with Br (Br-DTN) or site diluted. Quantum Monte Carlo simulations for the quantum phase transition of the model Hamiltonian for Br-DTN, as well as for site-diluted DTN, are consistent with conventional scaling at the quantum critical point and with a critical exponent $z$ verifying the prediction $z = d$; moreover the correlation length exponent is found to be $ν = 0.75(10)$, and the order parameter exponent to be $β = 0.95(10)$. We investigate the low-temperature thermodynamics at the quantum critical field of Br-DTN both numerically and experimentally, and extract the power-law behavior of the magnetization and of the specific heat. Our results for the exponents of the power laws, as well as previous results for the scaling of the critical temperature to magnetic ordering with the applied field, are incompatible with the conventional crossover-scaling Ansatz proposed by Fisher et al. [Phys. Rev. B 40, 546 (1989)]. However they can all be reconciled within a phenomenological Ansatz in the presence of a dangerously irrelevant operator.},

doi = {10.1103/physrevb.86.134421},

journal = {Physical Review. B, Condensed Matter and Materials Physics},

number = 13,

volume = 86,

place = {United States},

year = {2012},

month = {10}

}

*Citation information provided by*

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Web of Science

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