Understanding the interplay between the inherent disorder and the correlated fluctuating-spin ground state is a key element in the search for quantum spin liquids. H3LiIr2O6is considered to be a spin liquid that is proximate to the Kitaev-limit quantum spin liquid. Its ground state shows no magnetic order or spin freezing as expected for the spin liquid state. However, hydrogen zero-point motion and stacking faults are known to be present. The resulting bond disorder has been invoked to explain the existence of unexpected low-energy spin excitations, although data interpretation remains challenging. Here, we use resonant X-ray spectroscopies to map the collective excitations in H3LiIr2O6and characterize its magnetic state. In the low-temperature correlated state, we reveal a broad bandwidth of magnetic excitations. The central energy and the high-energy tail of the continuum are consistent with expectations for dominant ferromagnetic Kitaev interactions between dynamically fluctuating spins. Furthermore, the absence of a momentum dependence to these excitations are consistent with disorder-induced broken translational invariance. Our low-energy data and the energy and width of the crystal field excitations support an interpretation of H3LiIr2O6as a disordered topological spin liquid in close proximity to bond-disordered versions of the Kitaev quantum spin liquid.
The search for quantum spin liquids—topological magnets with fractionalized excitations—has been a central theme in condensed matter and materials physics. Despite numerous theoretical proposals, connecting experiment with detailed theory exhibiting a robust quantum spin liquid has remained a central challenge. Here, focusing on the strongly spin-orbit coupled effective
- NSF-PAR ID:
- 10381739
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- npj Quantum Materials
- Volume:
- 7
- Issue:
- 1
- ISSN:
- 2397-4648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract We report on the largest open‐shell graphenic bilayer and also the first example of triply negatively charged radical π‐dimer. Upon three‐electron reduction, bilayer nanographene fragment molecule (C96H24Ar6)2(Ar=2,6‐dimethylphenyl) (
1 2) was transformed to a triply negatively charged species1 23.−, which has been characterized by single‐crystal X‐ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic properties on a superconducting quantum interference device (SQUID).1 23.−features a 96‐center‐3‐electron (96c /3e ) pancake bond with a doublet ground state, which can be thermally excited to a quartet state. It consists of 34 π‐fused rings with 96 conjugatedsp 2carbon atoms. Spin frustration is observed with the frustration parameterf >31.8 at low temperatures in1 23.−, which indicates graphene upon reduction doping may behave as a quantum spin liquid. -
more » « less
Abstract We report on the largest open‐shell graphenic bilayer and also the first example of triply negatively charged radical π‐dimer. Upon three‐electron reduction, bilayer nanographene fragment molecule (C96H24Ar6)2(Ar=2,6‐dimethylphenyl) (
1 2) was transformed to a triply negatively charged species1 23⋅−, which has been characterized by single‐crystal X‐ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic properties on a superconducting quantum interference device (SQUID).1 23⋅−features a 96‐center‐3‐electron (96c /3e ) pancake bond with a doublet ground state, which can be thermally excited to a quartet state. It consists of 34 π‐fused rings with 96 conjugatedsp 2carbon atoms. Spin frustration is observed with the frustration parameterf >31.8 at low temperatures in1 23⋅−, which indicates graphene upon reduction doping may behave as a quantum spin liquid. -
more » « less
Abstract Tidal heating on Io due to its finite eccentricity was predicted to drive surface volcanic activity, which was subsequently confirmed by the Voyager spacecraft. Although the volcanic activity in Io is more complex, in theory volcanism can be driven by runaway melting in which the tidal heating increases as the mantle thickness decreases. We show that this runaway melting mechanism is generic for a composite planetary body with liquid core and solid mantle, provided that (i) the mantle rigidity,
μ , is comparable to the central pressure, i.e.,μ /(ρ gR P) ≳ 0.1 for a body with densityρ , surface gravitational accelerationg , and radiusR P; (ii) the surface is not molten; (iii) tides deposit sufficient energy; and (iv) the planet has nonzero eccentricity. We calculate the approximate liquid core radius as a function ofμ /(ρ gR P), and find that more than 90% of the core will melt due to this runaway forμ /(ρ gR P) ≳ 1. From all currently confirmed exoplanets, we find that the terrestrial planets in the L 98-59 system are the most promising candidates for sustaining active volcanism. However, uncertainties regarding the quality factors and the details of tidal heating and cooling mechanisms prohibit definitive claims of volcanism on any of these planets. We generate synthetic transmission spectra of these planets assuming Venus-like atmospheric compositions with an additional 5%, 50%, and 98% SO2component, which is a tracer of volcanic activity. We find a ≳3σ preference for a model with SO2with 5–10 transits with JWST for L 98-59bcd. -
more » « less
Abstract Detecting proximities between nuclei is crucial for atomic‐scale structure determination with nuclear magnetic resonance (NMR) spectroscopy. Different from spin‐1/2 nuclei, the methodology for quadrupolar nuclei is limited for solids due to the complex spin dynamics under simultaneous magic‐angle spinning (MAS) and radio‐frequency irradiation. Herein, the performances of several homonuclear rotary recoupling (HORROR)‐based homonuclear dipolar recoupling sequences are evaluated for27Al (spin‐5/2). It is shown numerically and experimentally on mesoporous alumina that
outperforms the supercycled S3sequence and its pure double‐quantum (DQ) (bracketed) version, [S3], both in terms of DQ transfer efficiency and bandwidth. This result is surprising since the S3sequence is among the best low‐power recoupling schemes for spin‐1/2. The superiority of is thoroughly explained, and the crucial role of radio‐frequency offsets during its spin dynamics is highlighted. The analytical approximation of , derived in an offset‐toggling frame, clarifies the interplay between offset and DQ efficiency, namely, the benefits of off‐resonance irradiation and the trough in DQ efficiency for when the irradiation is central between two resonances, both for spin‐1/2 and half‐integer‐spin quadrupolar nuclei. Additionally, density matrix propagations show that the sequence, applied to quadrupolar nuclei subject to quadrupolar interaction much larger than radio‐frequency frequency field, can create single‐ and multiple‐quantum coherences for near on‐resonance irradiation. This significantly perturbs the creation of DQ coherences between central transitions of neighboring quadrupolar nuclei. This effect explains the DQ efficiency trough for near on‐resonance irradiation, in the case of both cross‐correlation and autocorrelation peaks. Overall, this work aids experimental acquisition of homonuclear dipolar correlation spectra of half‐integer‐spin quadrupolar nuclei and provides theoretical insights towards improving recoupling schemes at high magnetic field and fast MAS.
