Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor

Le, Manh Duc; Quintero-Castro, D. L.; Toft-Petersen, Rasmus; Groitl, Felix; Skoulatos, M.; Rule, K. C.; Habicht, K.

doi:10.1016/j.nima.2013.07.007

Cited by 42 publications

(31 citation statements)

References 13 publications

(16 reference statements)

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“…Inelastic neutron scattering measurements were carried out on the ThALES cold triple-axis spectrometer at the Institut LaueLangevin, Grenoble, France and the FLEXX cold triple-axis spectrometer in the BER-II reactor at Helmholtz-Zentrum Berlin, Germany 32 . For the ThALES experiment, silicon (111) was used as a monochromator and analyzer; the final neutron energies were fixed at E f = 3 meV (energy resolution ∼ 0.05 meV), E f = 3.5 meV (energy resolution ∼ 0.08 meV) or E f = 4 meV (energy resolution ∼ 0.1 meV).…”

Section: Neutron Scattering Experimentsmentioning

confidence: 99%

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

Shen

et al. 2016

Nature

342

385

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A quantum spin liquid is an exotic quantum state of matter in which spins are highly entangled and remain disordered down to zero temperature. Such a state of matter is potentially relevant to high-temperature superconductivity and quantum-information applications, and experimental identification of a quantum spin liquid state is of fundamental importance for our understanding of quantum matter. Theoretical studies have proposed various quantum-spin-liquid ground states [1][2][3][4] , most of which are characterized by exotic spin excitations with fractional quantum numbers (termed 'spinon'). Here, we report neutron scattering measurements that reveal broad spin excitations covering a wide region of the Brillouin zone in a triangular antiferromagnet YbMgGaO 4 . The observed diffusive spin excitation persists at the lowest measured energy and shows a clear upper excitation edge, which is consistent with the particle-hole excitation of a spinon Fermi surface. Our results therefore point to a QSL state with a spinon Fermi surface in YbMgGaO 4 that has a perfect spin-1/2 triangular lattice as in the original proposal 4 of quantum spin liquids.In 1973, Anderson proposed the pioneering idea of the quantum spin liquid (QSL) in the study of the triangular lattice Heisenberg antiferromagnet 4 . This idea was revived after the discovery in 1986 of high-temperature superconductivity 5 . A QSL, as currently understood, does not fit into Landau's conventional paradigm of symmetry breaking phases 1,2,6,7 , and is arXiv:1607.02615v2 [cond-mat.str-el] 31 Jul 2017 2 instead an exotic state of matter characterized by spinon excitations and emergent gauge structures [1][2][3]6 . The search for QSLs in models and materials [8][9][10][11][12] has been partly facilitated by the Oshikawa-Hastings-Lieb-Schultz-Mattis (OHLSM) theorem that may hint at the possibility of QSLs in Mott insulators with odd electron fillings and a global U(1) spin rotational symmetry [13][14][15] .Indeed, a continuum of spin excitations has been observed in a kagome-lattice material ZnCu 3 (OD) 6 Cl 2 (refs 12,16). However, the requirement of the U(1) spin rotational symmetry, prevents the application of OHLSM theorem in strong spin-orbit-coupled (SOC) Mott insulators in which the spin rotational symmetry is completely absent. A recent theory addressed this limitation of the OHLSM theorem, arguing that, as long as time-reversal symmetry is preserved, the ground state of an SOC Mott insulator with odd electron fillings must be exotic 17 .The newly discovered triangular antiferromagnet YbMgGaO 4 (refs 18,19) displays no indication of magnetic ordering or symmetry breaking at temperatures as low as 30 mK despite approximately 4 K for the spin interaction energy scale. Because of the strong SOC of the Yb electrons, YbMgGaO 4 was the first QSL to be proposed beyond the OHLSM theorem 19 . The thirteen 4 f electrons of the Yb 3+ ion form the spin-orbit-entangled Kramers doublets that are split by the D 3d crystal electric fields [20][21][22] . At temperatures co...

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Section: Neutron Scattering Experimentsmentioning

confidence: 99%

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

Shen

et al. 2016

Nature

342

385

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“…The energy widths and normalized intensity for each of the channels are given in Table 1. The energy resolution for all channels is comparable to the standard FLEXX resolution [4], due to the fact that the vertical angular coverage of the analyzers is rather small. It is interesting to note that the increased intensity from having a large resolution volume in the high E f channels (V E f res ∝ k 3 f / tan(θ A )) is almost cancelled out by the decrease in the covered solid angle from having the high E f channels located further away from the sample position.…”

Section: -P3 Epj Web Of Conferencesmentioning

confidence: 89%

“…We used the same virtual front-end setup as in Ref. [4], proven to accurately simulate the real beam at the sample position. We simulated each energy channel separately at a fixed 2θ in W-configuration.…”

Section: -P3 Epj Web Of Conferencesmentioning

confidence: 99%

“…Simultaneously, the cold neutron triple axis spectrometer FLEX [2], a work-horse instrument for inelastic neutron scattering matching the low temperatures and high magnetic fields sample environment capabilities at HZB, was upgraded and relocated to a guide end position [3]. Experiments performed during the commissioning phase confirmed an order of magnitude gain in intensity as a result of the upgrade [4].…”

Section: Introductionmentioning

confidence: 99%

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The upgraded cold neutron triple-axis spectrometer FLEXX – enhanced capabilities by new instrumental options

Habicht

Quintero-Castro

Toft-Petersen

et al. 2015

EPJ Web of Conferences

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Abstract. The upgrade of the cold neutron triple axis spectrometer FLEXX, a work-horse instrument for inelastic neutron scattering matching the sample environment capabilities at Helmholtz-Zentrum Berlin, has been successfully accomplished. Experiments confirmed an order of magnitude gain in flux now allowing for intensity demanding options to be fully exploited at FLEXX. In this article, we describe the layout and design of two newly available FLEXX instrument options in detail. The new Heusler analyzer gives an increase of the detected polarized neutron flux due to its superior focusing properties, significantly improving the feasibility of future polarized and neutron resonance spin echo experiments. The MultiFLEXX option provides simultaneous access to large regions in wavevector and energy space for inelastic excitations thus adding mapping capabilities to the spectrometer.

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“…The crystal was aligned with the neutron beam perpendicular to the crystallographic b axis. Neutron data were collected on the three-axes spectrometers IN14 at ILL and FLEXX at HZB, 24 as well as on the timeof-flight multi-chopper spectrometer LET at ISIS. A 150 kOe (IN14), a 148 kOe (FLEXX) and a 140 kOe (LET) vertical magnet (H || b) with dilution insert were used.…”

Section: Methodsmentioning

confidence: 99%

Finite-temperature scaling of spin correlations in an experimental realization of the one-dimensional Ising quantum critical point

et al. 2015

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Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor

Cited by 42 publications

References 13 publications

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

The upgraded cold neutron triple-axis spectrometer FLEXX – enhanced capabilities by new instrumental options

Finite-temperature scaling of spin correlations in an experimental realization of the one-dimensional Ising quantum critical point

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