Michi-To Suzuki

Emergent rank-5 nematic order in URu 2 Si 2

Uranium ruthenium silicide exhibits a discontinuity in its specific heat at 17.5 K. The underlying cause of this anomaly is hotly debated. A first-principles study of high-order correlations in its electronic structure suggests this behaviour is the result of the emergence of rank-5 nematic order.

Anomalous Fermi surface in FeSe seen by Shubnikov–de Haas oscillation measurements

We have observed Shubnikov-de Haas oscillations in FeSe. The Fermi surface deviates significantly from predictions of band-structure calculations and most likely consists of one electron and one hole thin cylinder. The carrier density is in the order of 0.01 carriers/ Fe, an order-of-magnitude smaller than predicted. Effective Fermi energies as small as 3.6 meV are estimated. These findings call for elaborate theoretical investigations incorporating both electronic correlations and orbital ordering.

Evidence for magnetic Weyl fermions in a correlated metal

Weyl fermions have been observed as three-dimensional, gapless topological excitations in weakly correlated, inversion-symmetry-breaking semimetals. However, their realization in spontaneously time-reversal-symmetry-breaking phases of strongly correlated materials has so far remained hypothetical. Here, we report experimental evidence for magnetic Weyl fermions in Mn3Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect, even at room temperature. Detailed comparison between angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions-namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. Since weak magnetic fields (approximately 10 mT) are adequate to control the distribution of Weyl points and the large fictitious fields (equivalent to approximately a few hundred T) produced by them in momentum space, our discovery lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems such as Mn3Sn.

Electronic structure theory of the hidden-order material URu2Si2

We report a comprehensive electronic structure investigation of the paramagnetic (PM), the large moment antiferromagnetic (LMAF), and the hidden order (HO) phases of URu2Si2. We have performed relativistic full-potential calculations on the basis of the density-functional theory, employing different exchange-correlation functionals to treat electron correlations within the open 5f shell of uranium. Specifically, we investigate-through a comparison between calculated and low-temperature experimental properties-whether the 5f electrons are localized or delocalized in URu2Si2. The local spin-density approximation (LSDA) and generalized gradient approximation (GGA) are adopted to explore itinerant 5f behavior, the GGA plus additional strong Coulomb interaction (GGA+U approach) is used to approximate moderately localized 5f states, and the 5f-core approximation is applied to probe potential properties of completely localized uranium 5f states. We also performed local-density approximation plus dynamical mean-field theory calculations (DMFT) to investigate the temperature evolution of the quasiparticle states at 100 K and above, unveiling a progressive opening of a quasiparticle gap at the chemical potential when temperature is reduced. A detailed comparison of calculated properties with known experimental data demonstrates that the LSDA and GGA approaches, in which the uranium 5f electrons are treated as itinerant, provide an excellent explanation of the available low-temperature experimental data of the PM and LMAF phases. We show furthermore that due to a material-specific Fermi-surface instability a large, but partial, Fermi-surface gapping of up to 750 K occurs upon antiferromagnetic symmetry breaking. The occurrence of the HO phase is explained through dynamical symmetry breaking induced by a mode of long-lived antiferromagnetic spin fluctuations. This dynamical symmetry breaking model explains why the Fermi-surface gapping in the HO phase is similar but smaller than that in the LMAF phase and it also explains why the HO and LMAF phases have the same Fermi surfaces yet different order parameters. A suitable order parameter for the HO is proposed to be the Fermi-surface gap, and the dynamic spin-spin correlation function is further suggested as a secondary order parameter.

Change of Fermi Surface Topology in CeRu2Si2 Studied by LSDA plus U Method

The detailed electronic structures of CeRu2Si2 have been investigated for a nonmagnetic state and a magnetic state under magnetic fields by in LSDA+U method. It is found that the Si position in the crystal structure is an essential parameter to reproduce precise topology of the experimentally determined Fermi surfaces of non-f reference LaRu2Si2. As for CeRu2Si2, the LDA calculation Lids to predict the nonmagnetic round state, which is experimentally reported to be Mainly occupied by vertical bar j = 5/2.j(z) = +/- 5/2 > orbitals, and the Fermi surfaces. The nonmagnetic case solution of LSDA+U method greatly improves the electronic structure in the nonmagnetic CeRu2Si2. An LSDA+U method is also applied to investigate the electronic Structure under applied magnetic fields, then the change of the so-called large Fermi Surfaces to small Fermi surfaces is Successfully described.

Change of Fermi Surface Topology in CeRu2Si2 Studied by LSDA+U Method

The detailed electronic structures of CeRu2Si2 have been investigated for a nonmagnetic state and a magnetic state under magnetic fields by in LSDA+U method. It is found that the Si position in the crystal structure is an essential parameter to reproduce precise topology of the experimentally determined Fermi surfaces of non-f reference LaRu2Si2. As for CeRu2Si2, the LDA calculation Lids to predict the nonmagnetic round state, which is experimentally reported to be Mainly occupied by vertical bar j = 5/2.j(z) = +/- 5/2 > orbitals, and the Fermi surfaces. The nonmagnetic case solution of LSDA+U method greatly improves the electronic structure in the nonmagnetic CeRu2Si2. An LSDA+U method is also applied to investigate the electronic Structure under applied magnetic fields, then the change of the so-called large Fermi Surfaces to small Fermi surfaces is Successfully described.

Cluster multipole theory for anomalous Hall effect in antiferromagnets

Here, the authors discover a missing link between antiferromagnetism and the Hall effect by introducing a theoretical framework based on a novel concept, cluster multipole (CMP), to characterize macroscopic magnetization of antiferromagnets. Whereas the anomalous Hall effect (AHE) is usually observed in ferromagnets and explained as an outcome of the macroscopic dipole magnetization, CMP theory reveals that a certain type of antiferromagnetic (AFM) structure induces the AHE despite no net magnetization. The new order parameters enable us to characterize the AHE in the AFM states and explain the AHE in the AFM states of Mn

Emergent Loop-Nodal s ± -Wave Superconductivity in CeCu 2 Si 2 : Similarities to the Iron-Based Superconductors

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Catastrophic Fermi Surface Reconstruction in the Shape-Memory Alloy AuZn

Ir and Mn

Microscopic theory of the insulating electronic ground states of the actinide dioxides AnO2 (An =U, Np, Pu, Am, and Cm)

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