The social cerebellum: A large-scale investigation of functional and structural specificity and connectivity

The cerebellum has been traditionally disregarded in relation to nonmotor functions, but recent findings indicate it may be involved in language, affective processing, and social functions. Mentalizing, or Theory of Mind (ToM), is the ability to infer mental states of others and this skill relies on a distributed network of brain regions. Here, we leveraged large-scale multimodal neuroimaging data to elucidate the structural and functional role of the cerebellum in mentalizing. We used functional activations to determine whether the cerebellum has a domain-general or domain-specific functional role, and effective connectivity and probabilistic tractography to map the cerebello-cerebral mentalizing network. We found that the cerebellum is organized in a domain-specific way and that there is a left cerebellar effective and structural lateralization, with more and stronger effective connections from the left cerebellar hemisphere to the right cerebral mentalizing areas, and greater cerebello-thalamo-cortical and cortico-ponto-cerebellar streamline counts from and to the left cerebellum. Our study provides novel insights to the network organization of the cerebellum, an overlooked brain structure, and mentalizing, one of humans\u27 most essential abilities to navigate the social world

Magnetic structure, phase diagram, and a new type of spin-flop transition dominated by higher order interaction in a localized 5f system U3Pd20Si6

The magnetic structure of the localized-5f uranium intermetallic compound U3Pd20Si6 has been determined by means of a neutron diffraction experiment. Our data demonstrate that this compound has a collinear coupling of the sublattice ordering of the uranium spins on the 4a and 8c sites. We conclude that higher-order exchange and/or quadrupole interactions are necessary to stabilize this unique collinear structure. We discovered a new type of spin-flop transition against the uniaxial anisotropy induced by this collinear coupling

Magnetic Excitations in NpCoGa5

We report the results of inelastic neutron scattering experiments on NpCoGa$_{5}$, an isostructural analogue of the PuCoGa$_{5}$ superconductor. Two energy scales characterize the magnetic response in the antiferromagnetic phase. One is related to a non-dispersive excitation between two crystal field levels. The other at lower energies corresponds to dispersive fluctuations emanating from the magnetic zone center. The fluctuations persist in the paramagnetic phase also, although weaker in intensity. This supports the possibility that magnetic fluctuations are present in PuCoGa$_{5}$, where unconventional d-wave superconductivity is achieved in the absence of magnetic order.Comment: 4 pages, 5 figure

Magnetic Properties of a Pressure-induced Superconductor UGe2_2

We performed the DC-magnetization and neutron scattering experiments under pressure {\it P} for a pressure-induced superconductor UGe$_2$. We found that the magnetic moment is enhanced at a characteristic temperature {\it T}$^{*}$ in the ferromagnetic state, where {\it T}$^{*}$ is smaller than a Curie temperature {\it T}$_{\rm C}$. This enhancement becomes remarkable in the vicinity of {\it P}$_{\rm C}^{*}$ = 1.20 GPa, where {\it T}$^{*}$ becomes 0 K and the superconducting transition temperature {\it T}$_{\rm SC}$ shows a maximum. The characteristic temperature {\it T}$^{*}$, which decreases with increasing pressure, also depends on the magnetic field.Comment: To be published in J.Phys.Soc.Jp

The dual nature of 5f electrons and origin of heavy fermions in U compounds

We develop a theory for the electronic excitations in UPt$_3$ which is based on the localization of two of the $5f$ electrons. The remaining $f$ electron is delocalized and acquires a large effective mass by inducing intra-atomic excitations of the localized ones. The measured deHaas-vanAlphen frequencies of the heavy quasiparticles are explained as well as their anisotropic heavy mass. A model calculation for a small cluster reveals why only the largest of the different $5f$ hopping matrix elements is operative causing the electrons in other orbitals to localize.Comment: 6 pages, 3 figure

Emergent Nodal Excitations due to the Coexistence of Superconductivity and Antiferromagnetism: Cases with and without Inversion Symmetry

We argue the emergence of nodal excitations due to the coupling with static antiferromagnetic order in fully-gapped superconducting states in both cases with and without inversion symmetry. This line node structure is not accompanied with the sign change of the superconducting gap, in contrast to usual unconventional Cooper pairs with higher angular momenta. In the case without inversion symmetry, the stability of the nodal excitations crucially depends on the direction of the antiferromagnetic staggered magnetic moment. A possible realization of this phenomenon in CePt$_3$Si is discussed.Comment: 4 pages, 7 figure

Quasiparticles in a strongly correlated liquid with the fermion condensate: applications to high-temperature superconductors

A model of a strongly correlated electron liquid based on the fermion condensation (FC) is extended to high-temperature superconductors. Within our model, the appearance of FC presents a boundary separating the region of a strongly interacting electron liquid from the region of a strongly correlated electron liquid. We study the superconductivity of a strongly correlated liquid and show that under certain conditions, the superconductivity vanishes at temperatures $T>T_c\simeq T_{node}$, with the superconducting gap being smoothly transformed into a pseudogap. As the result, the pseudogap occupies only a part of the Fermi surface. The gapped area shrinks with increasing the temperature and vanishes at $T=T^*$. The single-particle excitation width is also studied. The quasiparticle dispersion in systems with FC can be represented by two straight lines characterized by the respective effective masses $M^*_{FC}$ and $M^*_L$, and intersecting near the binding energy that is of the order of the superconducting gap. It is argued that this strong change of the quasiparticle dispersion at the binding can be enhanced in underdoped samples because of strengthening the FC influence. The FC phase transition in the presence of the superconductivity is examined, and it is shown that this phase transition can be considered as kinetic energy driven.Comment: 16 pages, 3 figures, minor grammatical changes, revised and accepted by JET

Novel Pressure Phase Diagram of Heavy Fermion Superconductor CePt3_{3}Si Investigated by ac Calorimetry

The pressure dependences of the antiferromagnetic and superconducting transition temperatures have been investigated by ac heat capacity measurement under high pressures for the heavy-fermion superconductor CePt$_3$Si without inversion symmetry in the tetragonal structure. The N\'{e}el temperature $T_{\rm N}$ = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure $P_{\rm AF}$ $\simeq$ 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The pressure phase diagram of CePt$_3$Si is thus very unique and has never been reported before for other heavy fermion superconductors.Comment: 4 pages and 3 figures. This paper will be published in the July issue of J. Phys. Soc. Jp