top of page

Highly entangled liquid states in frustrated magnets

From light years away

A whisper from an unknown

Altered density

Among the many mind-blowing facets of quantum mechanics, probably the most bizarre one is the non-local entanglement – particles that are light-years away can instantly communicate with one another. This seemingly paradoxical feature rules the microscopic world: two electron spins forming a singlet state (i.e., up-down configuration) are entangled. The wavefunction of the individual spin is no longer well defined. In the pioneer paper about quantum entanglement by Schrodinger, he described this term as “the best possible knowledge of a whole does not necessarily include the best possible knowledge of all its parts.”  Researchers have demonstrated that entanglement is far more than just a fascinating theoretical concept. Rather, it is an invaluable physical resource that may revolutionize our ways of collecting and processing information– the rapidly emerging field of quantum information and computing.


One fascinating creation by quantum entanglement is a quantum spin liquid (QSL) – an intrinsic topological order without spontaneous symmetry breaking. The QSL is like a “magical ballroom” of magnetic moments, where they dance in an entangled and dynamical way, with infinitely many partners simultaneously. The long-range entanglement makes QSL a fertile ground for exotic low-energy excitations with fractional quantum statistics; some of those bear striking similarities with fundamental particles that shy away from detection in high energy experiments. A natural route to a QSL is magnetic frustration; namely, the magnetic interaction energies cannot be simultaneously minimized, leading to robust quantum fluctuations that avoid a long-range magnetic order even at absolute zero. The experimental quest for a QSL has been the central goal of the frustrated magnetism community for decades; if proven to exist, QSLs would be an exciting step toward next-generation quantum information technologies. The publications below describe our contributions to this extremely challenging yet exciting exploration. Please feel free to check them out.

用語解説 (用語をクリックすると説明が展開します)

Highly entangled liquid states in frustrated magnets


Spin–orbital liquid state and liquid–gas metamagnetic transition on a pyrochlore lattice

N. Tang, Y. Gritsenko, K. Kimura, S. Bhattacharjee, A. Sakai, M. Fu, H. Takeda, H. Man, K. Sugawara, Y. Matsumoto, Y. Shimura, J. Wen, C. Broholm, H. Sawa, M. Takigawa, T. Sakakibara, S. Zherlitsyn, J. Wosnitza, R. Moessner, S. Nakatsuji, Nat. Phys. 19, 92 (2023).

Crystal structures with degenerate electronic orbitals are unstable towards lattice distortions that lift the degeneracy. Although these Jahn–Teller distortions have profound effects on magnetism, they are typically unaffected by the onset of magnetic ordering because of a separation in energy scales. Here we show the contrary case in Pr2Zr2O7, where orbital degeneracy remains down to the millikelvin range due to an interplay between spins and orbitals. Pr2Zr2O7 is a multipolar spin ice with strongly localized 4f electrons in an even-number configuration, giving rise to a non-Kramers doublet that carries transverse quadrupolar and longitudinal dipolar moments. Our study of ultrapure single crystals of Pr2Zr2O7 finds comprehensive evidence for enhanced spin–orbital quantum dynamics of the non-Kramers doublet. This dynamical Jahn–Teller effect is encapsulated by the liquid–gas metamagnetic transition that is characteristic of spin ice being accompanied by strong lattice softening. This behaviour suggests that a spin–orbital liquid state forms on the pyrochlore lattice at low temperatures and low magnetic fields.


© The Author(s), under exclusive licence to Springer Nature Limited 2022

bottom of page