Scientific Review: The Triple Axis Spin-Echo Spectrometer TRISP at the FRM II

Keller, T.; Aynajian, Pegor; Bayrakci, S. P.; Buchner, K.; Habicht, K.; Klann, H.; Ohl, Michael; Keimer, B.

doi:10.1080/10448630701328372

Cited by 10 publications

(8 citation statements)

References 11 publications

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“…2(b)] around non-Hermitian Weyl points in three-dimensions. While observation of such features experimentally is potentially challenging given their small extent in wave-vector and energy, progress should be possible through careful studies using time-of-flight instruments or perhaps using specialized techniques such as NRSE [64,65].…”

Section: Non-hermitian Magnon Hamiltoniansmentioning

confidence: 99%

Non-Hermitian topology of spontaneous magnon decay

McClarty

Rau

2019

Phys. Rev. B

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Spontaneous magnon decay is a generic feature of the magnetic excitations of anisotropic magnets and isotropic magnets with non-collinear order. In this paper, we argue that the effect of interactions on one-magnon states can, under many circumstances, be treated in terms of an effective, energy independent, non-Hermitian Hamiltonian for the magnons. In the vicinity of Dirac or Weyl touching points, we show that the spectral function has a characteristic anisotropy arising from topologically protected exceptional points or lines in the non-Hermitian spectrum. Such features can, in principle, be detected using inelastic neutron scattering or other spectroscopic probes. We illustrate this physics through a concrete example: a honeycomb ferromagnet with Dzyaloshinskii-Moriya exchange. We perform interacting spin wave calculations of the structure factor and spectral function of this model, showing good agreement with results from a simple effective non-Hermitian model for the splitting of the Dirac point. Finally, we argue that the zoo of known topological protected magnon band structures may serve as a nearly ideal platform for realizing and exploring non-Hermitian physics in solidstate systems.arXiv:1904.02160v1 [cond-mat.str-el]

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Section: Non-hermitian Magnon Hamiltoniansmentioning

confidence: 99%

Non-Hermitian topology of spontaneous magnon decay

McClarty

Rau

2019

Phys. Rev. B

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“…To achieve τ M = 1 µs with this setup, the coils have to be driven at ω 1 = 2π • 1 MHz and ω 2 = 2π • 2 MHz so that ω M = 2π • 2 MHz. This can be obtained with current coil designs: RF coils that can be driven at these frequencies are 0 0.01 0.02 0.03 in commissioning at the instruments RESEDA [21] and TRISP [22] at FRM II. For these instrument parameters, a τ M -Q parameter space is opened as shown in figure 7 for cuboid samples of several sizes.…”

Section: High Resolution Misans At Essmentioning

confidence: 99%

Large scales–long times: Adding high energy resolution to SANS

Brandl

Georgii

Häußler

et al. 2011

Nuclear Instruments and Methods in Physics Research Section A:

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The Neutron Spin Echo (NSE) variant MIEZE (Modulation of IntEnsity by Zero Effort), where all beam manipulations are performed before the sample position, offers the possibility to perform low background SANS measurements in strong magnetic fields and depolarising samples. However, MIEZE is sensitive to differences ∆L in the length of neutron flight paths through the instrument and the sample. In this article, we discuss the major influence of ∆L on contrast reduction of MIEZE measurements and its minimisation. Finally we present a design case for enhancing a small-angle neutron scattering (SANS) instrument at the planned European Spallation Source (ESS) in Lund, Sweden, using a combination of MIEZE and other TOF options, such as TISANE offering time windows from ns to minutes. The proposed instrument would allow obtaining an excellent energy-and Q-resolution straightforward to µs for 0.01 Å −1 , even in magnetic fields, depolarising samples as they occur in soft matter and magnetism while keeping the instrumental effort and costs low.

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“…The LD measurements were performed at the thermal neutron resonance spin-echo spectrometer TRISP 29,30 at FRM II. Samples were loaded in a 3 He sorption system with a base temperature of 0.5 K, with helium exchange gas added above T = 5 K to extend the temperature range for data collection up to room temperature.…”

Section: Experimental Methodsmentioning

confidence: 99%

Neutron Larmor diffraction investigation of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho)

Ruminy,

Groitl,

Keller

et al. 2016

Preprint

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Scientific Review: The Triple Axis Spin-Echo Spectrometer TRISP at the FRM II

Cited by 10 publications

References 11 publications

Non-Hermitian topology of spontaneous magnon decay

Non-Hermitian topology of spontaneous magnon decay

Large scales–long times: Adding high energy resolution to SANS

Neutron Larmor diffraction investigation of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho)

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