34 research outputs found
Signatures of a Majorana-Fermi surface in the Kitaev magnet AgLiIrO
Detecting Majorana fermions in experimental realizations of the Kitaev
honeycomb model is often complicated by non-trivial interactions inherent to
potential spin liquid candidates. In this work, we identify several distinct
thermodynamic signatures of massive, itinerant Majorana fermions within the
well-established analytical paradigm of Landau-Fermi liquid theory. We find a
qualitative and quantitative agreement between the salient features of our
Landau-Majorana liquid theory and the Kitaev spin liquid candidate
AgLiIrO. Our study presents strong evidence for a Fermi liquid-like
ground state in the fundamental excitations of a honeycomb iridate, and opens
new experimental avenues to detect itinerant Majorana fermions in condensed
matter systems.Comment: 40 pages, 7 figure
Crystal Chemistry and Phonon Heat Capacity in Quaternary Honeycomb Delafossites: Cu[Li_(1/3)Sn_(2/3)]O)2 and Cu[Na_(1/3)Sn_(2/3)]O_2
This work presents an integrated approach to study the crystal chemistry and phonon heat capacity of complex layered oxides. Two quaternary delafossites are synthesized from ternary parent compounds and copper monohalides via a topochemical exchange reaction that preserves the honeycomb ordering of the parent structures. For each compound, Rietveld refinement of the powder X-ray diffraction patterns is examined in both monoclinic C2/c and rhombohedral R3Ì…m space groups. Honeycomb ordering occurs only in the monoclinic space group. Bragg peaks associated with honeycomb ordering acquire an asymmetric broadening known as the Warren line shape that is commonly observed in layered structures with stacking disorder. Detailed TEM analysis confirms honeycomb ordering within each layer in both title compounds and establishes a twinning between the adjacent layers instead of the more conventional shifting or skipping stacking faults. The structural model is then used to calculate phonon dispersions and heat capacity from first principles. In both compounds, the calculated heat capacity accurately describes the experimental data. The integrated approach presented here offers a platform to carefully analyze the phonon heat capacity in complex oxides where the crystal structure can produce magnetic frustration. Isolating phonon contribution from total heat capacity is a necessary and challenging step toward a quantitative study of spin liquid materials with exotic magnetic excitations such as spinons and Majorana fermions. A quantitative understanding of phonon density of states based on crystal chemistry as presented here also paves the way toward higher efficiency thermoelectric materials
Plethora of tunable Weyl fermions in kagome magnet Fe3Sn2 thin films
Interplay of magnetism and electronic band topology in unconventional magnets
enables the creation and fine control of novel electronic phenomena. In this
work, we use scanning tunneling microscopy and spectroscopy to study thin films
of a prototypical kagome magnet Fe3Sn2. Our experiments reveal an unusually
large number of densely-spaced spectroscopic features straddling the Fermi
level. These are consistent with signatures of low-energy Weyl fermions and
associated topological Fermi arc surface states predicted by theory. By
measuring their response as a function of magnetic field, we discover a
pronounced evolution in energy tied to the magnetization direction. Electron
scattering and interference imaging further demonstrates the tunable nature of
a subset of related electronic states. Our experiments provide the first
visualization of how in-situ spin reorientation drives changes in the
electronic density of states of the Weyl fermion band structure. Combined with
previous reports of massive Dirac fermions, flat bands and electronic
nematicity, our work establishes Fe3Sn2 as a unique platform that harbors an
extraordinarily wide array of topological and correlated electron phenomena
First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice
Recent observations of novel spin-orbit coupled states have generated
tremendous interest in transition metal systems. A prime example is the
state in iridate materials and -RuCl
that drives Kitaev interactions. Here, by tuning the competition between
spin-orbit interaction () and trigonal crystal field
splitting (), we restructure the spin-orbital wave functions
into a novel state that drives Ising interactions. This is
done via a topochemical reaction that converts LiRhO to
AgLiRhO, leading to an enhanced trigonal distortion and a
diminished spin-orbit coupling in the latter compound. Using perturbation
theory, we present an explicit expression for the new state
in the limit realized in
AgLiRhO, different from the conventional
state in the limit realized in LiRhO. The change of ground state is
followed by a dramatic change of magnetism from a 6 K spin-glass in
LiRhO to a 94 K antiferromagnet in AgLiRhO. These
results open a pathway for tuning materials between the two limits and creating
a rich magnetic phase diagram.Comment: 22 pages, 4 figure
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Plethora of tunable Weyl fermions in kagome magnet Fe3Sn2 thin films
Interplay of magnetism and electronic band topology in unconventional magnets enables the creation and fine control of novel electronic phenomena. In this work, we use scanning tunneling microscopy and spectroscopy to study thin films of a prototypical kagome magnet Fe3Sn2. Our experiments reveal an unusually large number of densely-spaced spectroscopic features straddling the Fermi level. These are consistent with signatures of low-energy Weyl fermions and associated topological Fermi arc surface states predicted by theory. By measuring their response as a function of magnetic field, we discover a pronounced evolution in energy tied to the magnetization direction. Electron scattering and interference imaging further demonstrates the tunable nature of a subset of related electronic states. Our experiments provide a direct visualization of how in-situ spin reorientation drives changes in the electronic density of states of the Weyl fermion band structure. Combined with previous reports of massive Dirac fermions, flat bands, and electronic nematicity, our work establishes Fe3Sn2 as an interesting platform that harbors an extraordinarily wide array of topological and correlated electron phenomena
Stripe Helical Magnetism and Two Regimes of Anomalous Hall Effect in NdAlGe
We report the magnetic and electronic transport properties of the inversion
and time-reversal symmetry breaking Weyl semimetal NdAlGe. This material is
analogous to NdAlSi, whose helical magnetism presents a rare example of a
Weyl-mediated collective phenomenon, but with a larger spin-orbit coupling. Our
neutron diffraction experiments revealed that NdAlGe, similar to NdAlSi,
supports an incommensurate Ising spin density wave ( K)
with a small helical spin canting of 3 and a long-wavelength of
35 nm, which transitions to a commensurate ferrimagnetic state below
K. Using small-angle neutron scattering, we showed that
the zero-field cooled ferrimagnetic domains form stripes in real space with
characteristic length scales of 18 nm and 72 nm parallel and perpendicular to
the [110] direction, respectively. Interestingly, for the transport properties,
NdAlSi does not exhibit an anomalous Hall effect (AHE) that is commonly
observed in magnetic Weyl semimetals. In contrast to NdAlSi, we identify two
different AHE regimes in NdAlGe that are respectively governed by intrinsic
Berry curvature and extrinsic disorders/spin fluctuations. Our study suggests
that Weyl-mediated magnetism prevails in this group of noncentrosymmetric
magnetic Weyl semimetals NdAl, but transport properties including AHE are
affected by material-specific extrinsic effects such as disorders, despite the
presence of prominent Berry curvature.Comment: Preprint, 16 pages, 6 main figures, 6 supplementary figure
The Health-Oriented Lifestyle in Islamic Culture
Introduction: Islam has always stressed the importance of health and wellness. For centuries, Muslims have recognized the value of a good, clean, and healthy life. The purpose of this study is to explain the health-oriented lifestyle in the Islamic culture based on opinions, experiences, and perceptions of clergies, teachers, and students. Method: A qualitative research method was conducted in this study by grounded theory approach. Data were gathered through semi-structured interviews with participants. Moreover, the existing resources, such as case studies, life stories, letters, diaries, and press interviews have been used. Results: This study's central variable was deviation from moderation of thought, belief and behavior. Seven main categories were gained by analysis of data. They were: "policy in the health system", "Islamic education"," Islamic movement in people's family centered lives", "work, effort, and money", "ethics and law abiding citizen", "mobility and leisure", "relationships, interaction, and participation". Conclusion: Lifestyle modification, in the process of acquiring healthy communities and social capital, based on religious teachings could be the perfect solution for the problems of a healthy life in the present day. In structural approach, the government should pay attention to such issues like authority of the family, and supporting parents, and spouses, facilitate family functions by systematic problem solving, and empower and strengthen institutions such as the education system and media. It is suggested that educational institutions direct their teachings toward empowering children of this society in order for them to better play their roles in family and social life, and encourage them to use Islamic teachings
Keywords: Health-oriented lifestyle, Islamic culture, Qualitative researc
Crystal Chemistry and Phonon Heat Capacity in Quaternary Honeycomb Delafossites: Cu[Li_(1/3)Sn_(2/3)]O)2 and Cu[Na_(1/3)Sn_(2/3)]O_2
This work presents an integrated approach to study the crystal chemistry and phonon heat capacity of complex layered oxides. Two quaternary delafossites are synthesized from ternary parent compounds and copper monohalides via a topochemical exchange reaction that preserves the honeycomb ordering of the parent structures. For each compound, Rietveld refinement of the powder X-ray diffraction patterns is examined in both monoclinic C2/c and rhombohedral R3Ì…m space groups. Honeycomb ordering occurs only in the monoclinic space group. Bragg peaks associated with honeycomb ordering acquire an asymmetric broadening known as the Warren line shape that is commonly observed in layered structures with stacking disorder. Detailed TEM analysis confirms honeycomb ordering within each layer in both title compounds and establishes a twinning between the adjacent layers instead of the more conventional shifting or skipping stacking faults. The structural model is then used to calculate phonon dispersions and heat capacity from first principles. In both compounds, the calculated heat capacity accurately describes the experimental data. The integrated approach presented here offers a platform to carefully analyze the phonon heat capacity in complex oxides where the crystal structure can produce magnetic frustration. Isolating phonon contribution from total heat capacity is a necessary and challenging step toward a quantitative study of spin liquid materials with exotic magnetic excitations such as spinons and Majorana fermions. A quantitative understanding of phonon density of states based on crystal chemistry as presented here also paves the way toward higher efficiency thermoelectric materials