7 research outputs found
The numerical renormalization group method for quantum impurity systems
In the beginning of the 1970's, Wilson developed the concept of a fully
non-perturbative renormalization group transformation. Applied to the Kondo
problem, this numerical renormalization group method (NRG) gave for the first
time the full crossover from the high-temperature phase of a free spin to the
low-temperature phase of a completely screened spin. The NRG has been later
generalized to a variety of quantum impurity problems. The purpose of this
review is to give a brief introduction to the NRG method including some
guidelines of how to calculate physical quantities, and to survey the
development of the NRG method and its various applications over the last 30
years. These applications include variants of the original Kondo problem such
as the non-Fermi liquid behavior in the two-channel Kondo model, dissipative
quantum systems such as the spin-boson model, and lattice systems in the
framework of the dynamical mean field theory.Comment: 55 pages, 27 figures, submitted to Rev. Mod. Phy
Modulated Kondo screening along magnetic mirror twin boundaries in monolayer MoS2 on graphene
A many-body resonance emerges at the Fermi energy when an electron bath
screens the magnetic moment of a half-filled impurity level. This Kondo effect,
originally introduced to explain the abnormal resistivity behavior in bulk
magnetic alloys, has been realized in many quantum systems over the past
decades, such as quantum dots, quantum point contacts, nanowires,
single-molecule transistors, heavy-fermion lattices, down to adsorbed single
atoms. Here we describe a unique Kondo system which allows us to experimentally
resolve the spectral function consisting of impurity levels and Kondo resonance
in a large Kondo temperature range, as well as their spatial modulation. Our
experimental Kondo system, based on a discrete half-filled quantum confined
state within a MoS2 grain boundary, in conjunction with numerical
renormalization group calculations, enables us to test the predictive power of
the Anderson model which is the basis of the microscopic understanding of Kondo
physics
Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy
Probing the universal low-temperature magnetic-field scaling of Kondo-correlated quantum dots via electrical conductance has proved to be experimentally challenging. Here, we show how to probe this in nonlinear thermocurrent spectroscopy applied to a molecular quantum dot in the Kondo regime. Our results demonstrate that the bias-dependent thermocurrent is a sensitive probe of universal Kondo physics, directly measures the splitting of the Kondo resonance in a magnetic field, and opens up possibilities for investigating nanosystems far from thermal and electrical equilibrium.QN/van der Zant La
Data supplementary to the publication: Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy
The experimental data and theoretical simulation for " Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy" published on Physical Review Letters.
In this letter, we show the universality in the Kondo effect via the thermocurrent spectroscopy. It is now a new hallmark for the Kondo effect in thermoelectricity. The experimental data are collected in electromigration break junction where a radical molecule resides.</p