Banca de DEFESA: HERNÁN GUILLERMO BUENO XAVIER

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : HERNÁN GUILLERMO BUENO XAVIER
DATE: 05/05/2023
TIME: 13:00
LOCAL: online
TITLE:

Network construction of non-Abelian topological phases

KEY WORDS:

Quantum Spin Liquids; Topological Phases of Matter; Spin Chains; Bosonization; Conformal Field Theory.

PAGES: 105
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In this thesis we use a network of chiral junctions to realize non-Abelian topological phases in two dimensions. Our
construction is based on boundary fixed points of low-energy field theories describing Y junctions of critical spin-chain
models. To set the stage, we first study a single junction of gapless spin-1 chains belonging to the SU(2)_2 universality class,
whose spectrum includes fractional excitations such as Majorana fermions. We find that chiral fixed points appear as special
points on a transition line that separates two regimes described by open boundary conditions. Remarkably, along this transition
the junction behaves as a tunable spin circulator as the spin conductance varies continuously with the coupling constant of a
marginal boundary operator. We then construct a family of topological chiral spin liquids departing from a honeycomb
network made of critical spin-S chains. The chiral spin liquid phase harbors SU(2)_{k=2S} anyons, which stem from the
underlying Wess-Zumino-Witten models that describe the constituent spin chains of the network. The network exhibits
quantized spin and thermal Hall conductances. We illustrate our construction by inspecting the topological properties of the
SU(2)_2 model. We find that this model has emergent Ising anyons, with spinons acting as vortex excitations that bind
Majorana zero modes. We also show that the ground state of this network is threefold degenerate on the torus, asserting its
non-Abelian character. Our work provides a controllable analytical framework to study non-Abelian topological phases,
sheding new light on the stability of such phases in artificial quantum materials.

COMMITTEE MEMBERS:
Interno - ***.839.841-** - DMITRY MELNIKOV - UFRN
Externo à Instituição - EDUARDO MIRANDA - UNICAMP
Externo à Instituição - HERMANN FREIRE FERREIRA LIMA E SILVA
Presidente - 1313663 - RODRIGO GONCALVES PEREIRA
Interno - 2195232 - TOMMASO MACRI