26 research outputs found
Anomaly/Transport in an Ideal Weyl gas
We study some of the transport processes which are specific to an ideal gas
of relativistic Weyl fermions and relate the corresponding transport
coefficients to various anomaly coefficients of the system. We propose that
these transport processes can be thought of as arising from the continuous
injection of chiral states and their subsequent adiabatic flow driven by
vorticity. This in turn leads to an elegant expression relating the anomaly
induced transport coefficients to the anomaly polynomial of the Ideal Weyl gas.Comment: 35 pages, JHEP forma
High field level crossing studies on spin dimers in the low dimensional quantum spin system NaT(CO)(HO) with T=Ni,Co,Fe,Mn
In this paper we demonstrate the application of high magnetic fields to study
the magnetic properties of low dimensional spin systems. We present a case
study on the series of 2-leg spin-ladder compounds
NaT(CO)(HO) with T = Ni, Co, Fe and Mn. In all
compounds the transition metal is in the high spin configuation. The
localized spin varies from S=1 to 3/2, 2 and 5/2 within this series. The
magnetic properties were examined experimentally by magnetic susceptibility,
pulsed high field magnetization and specific heat measurements. The data are
analysed using a spin hamiltonian description. Although the transition metal
ions form structurally a 2-leg ladder, an isolated dimer model consistently
describes the observations very well. This behaviour can be understood in terms
of the different coordination and superexchange angles of the oxalate ligands
along the rungs and legs of the 2-leg spin ladder. All compounds exhibit
magnetic field driven ground state changes which at very low temperatures lead
to a multistep behaviour in the magnetization curves. In the Co and Fe
compounds a strong axial anisotropy induced by the orbital magnetism leads to a
nearly degenerate ground state and a strongly reduced critical field. We find a
monotonous decrease of the intradimer magnetic exchange if the spin quantum
number is increased
Electron quantum metamaterials in van der Waals heterostructures
In recent decades, scientists have developed the means to engineer synthetic
periodic arrays with feature sizes below the wavelength of light. When such
features are appropriately structured, electromagnetic radiation can be
manipulated in unusual ways, resulting in optical metamaterials whose function
is directly controlled through nanoscale structure. Nature, too, has adopted
such techniques -- for example in the unique coloring of butterfly wings -- to
manipulate photons as they propagate through nanoscale periodic assemblies. In
this Perspective, we highlight the intriguing potential of designer
sub-electron wavelength (as well as wavelength-scale) structuring of electronic
matter, which affords a new range of synthetic quantum metamaterials with
unconventional responses. Driven by experimental developments in stacking
atomically layered heterostructures -- e.g., mechanical pick-up/transfer
assembly -- atomic scale registrations and structures can be readily tuned over
distances smaller than characteristic electronic length-scales (such as
electron wavelength, screening length, and electron mean free path). Yet
electronic metamaterials promise far richer categories of behavior than those
found in conventional optical metamaterial technologies. This is because unlike
photons that scarcely interact with each other, electrons in subwavelength
structured metamaterials are charged, and strongly interact. As a result, an
enormous variety of emergent phenomena can be expected, and radically new
classes of interacting quantum metamaterials designed
Recent Progress in Quantum Inverse Scattering Method — Baxter Hierarchy and Its Applications
Fermi liquids and Luttinger liquids
In these lecture notes, the basic physics of Fermi liquids and Luttinger liquids is presented. Fermi liquids are discussed both from a phenomenological viewpoint, in relation to microscopic approaches, and as renormalization group fixed points. Luttinger liquids are introduced using the bosonization formalism, and their essential differences with Fermi liquids are pointed out. Applications to transport effects, the effect of disorder, quantum spin chains, and spin ladders, both insulating and metallic, are given