Ryan Requist
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View article: Non-adiabaticity from first principles: the exact-factorization approach for solids
Non-adiabaticity from first principles: the exact-factorization approach for solids Open
The thorough treatment of electron-lattice interactions from first principles is one of the main goals in condensed matter physics. While the commonly applied adiabatic Born-Oppenheimer approximation is sufficient for describing many physi…
View article: Quantum covariant derivative: a tool for deriving adiabatic perturbation theory to all orders
Quantum covariant derivative: a tool for deriving adiabatic perturbation theory to all orders Open
The covariant derivative suitable for differentiating and parallel transporting tangent vectors and other geometric objects induced by a parameter-dependent adiabatic quantum eigenstate is introduced. It is proved to be covariant under gau…
View article: Adiabatic perturbation theory for two-component systems with one heavy component
Adiabatic perturbation theory for two-component systems with one heavy component Open
Perturbation theory with respect to the kinetic energy of the heavy component of a two-component quantum system is introduced. An effective Hamiltonian that is accurate to second order in the inverse heavy mass is derived. It contains a ne…
View article: Gauge- and coordinate-invariant equations for two-component systems
Gauge- and coordinate-invariant equations for two-component systems Open
The Schrödinger-like equations for the marginal and conditional probability amplitudes resulting from the exact factorization of the wavefunction of a two-component system are derived in a form that is invariant to gauge and coordinate tra…
View article: Quantum covariant derivative
Quantum covariant derivative Open
The covariant derivative capable of differentiating and parallel transporting tangent vectors and other geometric objects induced by a parameter-dependent quantum state is introduced. It is proved to be covariant under gauge and coordinate…
View article: Geometric energy transfer in two-component systems
Geometric energy transfer in two-component systems Open
Factoring a wave function into marginal and conditional factors partitions the subsystem kinetic energy into two terms. The first depends solely on the marginal wave function, through its gauge-covariant derivative, while the second depend…
View article: Fock-Space Embedding Theory: Application to Strongly Correlated Topological Phases
Fock-Space Embedding Theory: Application to Strongly Correlated Topological Phases Open
A many-body wave function can be factorized in Fock space into a marginal amplitude describing a set of strongly correlated orbitals and a conditional amplitude for the remaining weakly correlated part. The marginal amplitude is the soluti…
View article: The 2021 Room-Temperature Superconductivity Roadmap.
The 2021 Room-Temperature Superconductivity Roadmap. Open
Last year, the report of Room-Temperature Superconductivity in high-pressure carbonaceous sulfur hydride marked a major milestone in the history of physics: one of the holy grails of condensed matter research was reached after more than on…
View article: Fock space embedding theory for strongly correlated topological phases
Fock space embedding theory for strongly correlated topological phases Open
A many-body wave function can be factorized in Fock space into a marginal amplitude describing a set of strongly correlated orbitals and a conditional amplitude for the remaining weakly correlated part. The marginal amplitude is the soluti…
View article: Exact factorization-based density functional theory of electron-phonon systems
Exact factorization-based density functional theory of electron-phonon systems Open
Density functional theory is generalized to incorporate electron-phonon\ncoupling. A Kohn-Sham equation yielding the electronic density\n$n_U(\\mathbf{r})$, a conditional probability density depending parametrically\non the phonon normal m…
View article: Model Hamiltonian for strongly correlated systems: Systematic, self-consistent, and unique construction
Model Hamiltonian for strongly correlated systems: Systematic, self-consistent, and unique construction Open
An interacting lattice model describing the subspace spanned by a set of strongly-correlated bands is rigorously coupled to density functional theory to enable ab initio calculations of geometric and topological material properties. The st…
View article: Accurate Formula for the Macroscopic Polarization of Strongly Correlated Materials
Accurate Formula for the Macroscopic Polarization of Strongly Correlated Materials Open
The many-body Berry phase formula for macroscopic polarization is approximated by a sum of natural orbital geometric phases with fractional occupation numbers accounting for the dominant correlation effects. This formula accurately reprodu…
View article: Kondo physics of the Anderson impurity model by distributional exact diagonalization
Kondo physics of the Anderson impurity model by distributional exact diagonalization Open
The Distributional Exact Diagonalization (DED) scheme is applied to the\ndescription of Kondo physics in the Anderson impurity model. DED maps\nAnderson's problem of an interacting impurity level coupled to an infinite bath\nonto an ensemb…
View article: Exact Factorization-Based Density Functional Theory of Electrons and Nuclei
Exact Factorization-Based Density Functional Theory of Electrons and Nuclei Open
The ground state energy of a system of electrons (r=r_{1},r_{2},…) and nuclei (R=R_{1},R_{2},…) is proven to be a variational functional of the electronic density n(r,R) and paramagnetic current density j_{p}(r,R) conditional on R, the nuc…
View article: Density functional theory with quantum nuclei
Density functional theory with quantum nuclei Open
It is proved that the ground state energy of an electron-nuclear system is a variational functional of the conditional electronic density n_R(r), the nuclear wavefunction \chi(R) and the quantum geometric tensor of the conditional electron…
View article: Molecular geometric phase from the exact electron-nuclear factorization
Molecular geometric phase from the exact electron-nuclear factorization Open
The Born-Oppenheimer electronic wavefunction $\\Phi_R^{BO}(r)$ picks up a\ntopological phase factor $\\pm 1$, a special case of Berry phase, when it is\ntransported around a conical intersection of two adiabatic potential energy\nsurfaces …
View article: Energy-momentum mapping of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>d</mml:mi></mml:math>-derived Au(111) states in a thin film
Energy-momentum mapping of-derived Au(111) states in a thin film Open
The quantum well states of a film can be used to sample the electronic\nstructure of the parent bulk material and determine its band parameters. We\nhighlight the benefits of two-dimensional film band mapping, with respect to\ncomplex bulk…
View article: Co adatoms on Cu surfaces: Ballistic conductance and Kondo temperature
Co adatoms on Cu surfaces: Ballistic conductance and Kondo temperature Open
The Kondo zero bias anomaly of Co adatoms probed by scanning tunneling\nmicroscopy is known to depend on the height of the tip above the surface, and\nthis dependence is different on different low index Cu surfaces. On the (100)\nsurface, …