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Physics Department Presents a Condensed Matter Theory Seminar

Condensed Matter Theory:

Momentum-resolved electronic excitations in quasi-one dimensional quantum materials 


Alberto Nocera

Stewart Blusson Quantum Matter Institute, The University of British Columbia


The energy-momentum structure of electronic excitations of strongly correlated quantum systems provides crucial information about their complex physical behavior. Experimentally, most of the important features of electronic excitations are routinely accessed using angle resolved photoe-mission spectroscopy and neutron scattering techniques. In the last two decades, however, resonant inelastic x-ray scattering (RIXS) is emerging as a complementary tool to standard spectroscopic probes, giving simultaneus access to charge, orbital, and magnetic excitations. In all these cases, the computation of excitations spectra of 2D and 3D materials starting from model Hamiltonians is often a formidable task, particularly when many orbitals are active. In addition, as opposed to other response functions, RIXS is a second order process, described by a four-point two-particle Green’s function. Fortunately, certain quantum materials are made of weakly coupled quasi-1D building blocks, such as chains or ladders. In this case, theorists have the unique opportunity to study both the ground-state and excitations’ spectra of these systems with numerically exact techniques, such as the density matrix renormalization group method (DMRG).

In the first part of the talk, I will present a DMRG method for computing RIXS spectra of quasi-1D systems [1]. With this new procedure, I computed the low-energy magnetic excitations observed in Cu L-edge RIXS for the challenging corner shared CuO4 chains on cluster sizes well beyond state-of-the-art exact diagonalization techniques, using both multi-orbital and downfolded t-J model Hamiltonians.

In the second part of the talk, I will explore the magnetic [2], charge and orbital excitations’ spectra [3] of an effective model for the iron-based quantum ladder material BaFe2Se3. This material has recently attracted considerable attention because neutron scattering and RIXS experiments have shown evidence of a mixed character between correlated band-like and localized excitations (dubbed orbital selective Mott phase) cohexisting with an unusual “block” magnetic order.

Finally, I will discuss the implications of the results for experiments and outline future directions of research.


Wednesday, February 27, 2019 at 4:00pm to 5:00pm

Dana Research Center, 114 110 Forsyth St

Event Type



COS, Physics

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