Nonlinear gyration tensors for molecular crystals

Ovander, L. N.; Petrenko, A. D.

doi:10.1007/bf00633447

Cited by 9 publications

(15 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The symmetrized Raman tensor χ I,S (ω) for the different scattering geometries can be classified by the irreducible representations for the crystallographic point group 73 . The symmetry channels accessible by Raman scattering transform…”

Section: The Raman Probementioning

confidence: 99%

“…their symmetry [63][64][65][66] . The symmetrized Raman tensor for the different scattering geometries can be classified by the irreducible representations for the crystallographic point group 73 . The symmetry channels accessible by Raman scattering are A 1g , A 2g , B 1g , B 2g and E g for pnictides with a tetragonal 2-Fe unit cell, i.e.…”

Section: Overview Of Nafe1−xcoxas Raman Datamentioning

confidence: 99%

See 1 more Smart Citation

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

et al. 2016

View full text Add to dashboard Cite

The multiband nature of iron pnictides gives rise to a rich temperature-doping phase diagram of competing orders and a plethora of collective phenomena. At low dopings, the tetragonal-to-orthorhombic structural transition is closely followed by a spin density wave transition both being in close proximity to the superconducting phase. A key question is the nature of high-Tc superconductivity and its relation to orbital ordering and magnetism. Here we study the NaFe1−xCoxAs superconductor using polarization-resolved Raman spectroscopy. The Raman susceptibility displays critical enhancement of non-symmetric charge fluctuations across the entire phase diagram which are precursors to a d-wave Pomeranchuk instability at temperature θ(x). The charge fluctuations are interpreted in terms of quadrupole inter-orbital excitations in which the electron and hole Fermi surfaces breathe in-phase. Below Tc, the critical fluctuations acquire coherence and undergo a metamorphosis into a coherent ingap mode of extraordinary strength.

show abstract

Section: The Raman Probementioning

confidence: 99%

Section: Overview Of Nafe1−xcoxas Raman Datamentioning

confidence: 99%

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The scattering geometries used in this experiment are denoted as µν =RR, RL, XX and XY, probing A 1 +A 2 , 2E 2 , A 1 +E 2 and A 2 +E 2 symmetries of the C 6v group, respectively [32,51]. R = X + iY and L = X − iY denotes the right-and left-circular polarizations, respectively, where X (Y) denotes linear polarization parallel (perpendicular) to the plane of incidence.…”

Section: Raman Scatteringmentioning

confidence: 99%

Chiral Spin Mode on the Surface of a Topological Insulator

et al. 2017

View full text Add to dashboard Cite

Using polarization-resolved resonant Raman spectroscopy, we explore collective spin excitations of the chiral surface states in a three dimensional topological insulator, Bi2Se3. We observe a sharp peak at 150 meV in the pseudovector A2 symmetry channel of the Raman spectra. By comparing the data with calculations, we identify this peak as the transverse collective spin mode of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface plasmon in the charge sector of excitations, is analogous to a spin wave in a partially polarized Fermi liquid, with spin-orbit coupling playing the role of an effective magnetic field.Magnets and partially spin-polarized Fermi liquids support collective spin excitations (spin waves), in which all electron spins respond coherently to external fields, and the "glue" that locks the phases of precessing spins is provided by the exchange interaction. In nonmagnetic materials where inversion symmetry is broken but time-reversal invariance remains intact, strong spin-orbit coupling (SOC) may play the role of an effective magnetic field, which locks electron spins and momenta into textures. This phenomenon is encountered in threedimensional (3D) topological insulators (TIs), which harbor topologically protected surface states [1][2][3][4][5]. These states have been a focus of intense studies, both from the fundamental point-of-view [6][7][8][9][10][11][12] and for potential applications in spintronics devices [13][14][15][16][17][18][19][20]. However, the many-body interactions leading to collective effects in TIs remain largely unexplored. An essential aspect of this physics is an interplay between the Coulomb interaction and SOC, which is expected to give rise to a new type of collective spin excitations -chiral spin waves [21][22][23][24][25][26]. In the long wavelength (q = 0) limit, these modes are completely decoupled from the charge channel and thus distinct from spin-plasmons [27,28], Dirac plasmons [29,30], and surface plasmons in TIs [30,31].In this Letter, we employ polarization-resolved resonant Raman spectroscopy, a technique of choice for probing the collective charge [32,33], spin [34][35][36][37] and orbital excitations [38], to study collective spin excitations of the chiral surface states in Bi 2 Se 3 . To enhance the signal from the surface states, we tune the energy of incoming photons in resonance with a transition between two sets of chiral surface states: near the Fermi energy and about 1.8 eV above it [ Fig. 1(a)] [39]. We observe a long-lived excitation at 150 meV in the pseudovector symmetry channel of the Raman spectra, which is most pronounced at low temperatures but persists up to room temperature. By comparing the data with calculations, we identify this excitation as the transverse collective chiral spin mode supported by spin-polarized surface Dirac fermions. Such collective modes -first predicted for nontopological systems [21][22][23][24][25][26]36] but hitherto unobserved -are "peeled off" from the continuum of particle-hole excitations by t...

show abstract

“…the Raman tensors : if the projection to a particular symmetry species has any non-zero tensor element then a vibrational transition belonging to that symmetry species is Raman active in its fundamental. 23…”

Section: Selection Rules For a Regular Helical Polypeptidementioning

confidence: 99%

Polarized Raman spectra of oriented films of α-helical poly(L-alanine) and itsN-deuterated analogue

Lee

Krimm

1998

J. Raman Spectrosc.

View full text Add to dashboard Cite

Polarized Raman spectra were obtained on well oriented Ðlms of a-helical poly(L-alanine) (a-PLA) and its Ndeuterated analogue in order to obtain deÐnitive assignments of the modes. Such assignments were aided E 2-species by an analysis of factors that can lead to "cross-talkÏ between A, and spectra, viz. reÑection of the incident E 1 E 2 beam and non-perfect lateral and axial chain orientation in the sample. The convincing assignment of at least eleven signiÐcant modes in a-PLA has led to the reÐnement of a new empirical force Ðeld and a more detailed E 2 normal mode analysis.

show abstract

Nonlinear gyration tensors for molecular crystals

Cited by 9 publications

References 5 publications

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

Chiral Spin Mode on the Surface of a Topological Insulator

Polarized Raman spectra of oriented films of α-helical poly(L-alanine) and itsN-deuterated analogue

Contact Info

Product

Resources

About