Freiburg 2024 – scientific programme
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A: Fachverband Atomphysik
A 12: Bosonic Quantum Gases III (joint session Q/A)
A 12.3: Talk
Tuesday, March 12, 2024, 11:30–11:45, Aula
Strong-coupling expansion for disordered Bose-Hubbard model — •Renan da Silva Souza1, Axel Pelster2, and Francisco Ednilson Alves dos Santos3 — 1Goethe-Universität, Institut für Theoretische Physik, Frankfurt am Main, Germany — 2Physics Department and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Germany — 3Departamento de Física, Universidade Federal de São Carlos, Brazil
We identified the different ground states corresponding to the disordered Bose-Hubbard model at zero and finite temperatures and for small tunneling energies. Employing a field-theoretical approach, we constructed a strong-coupling expansion. By utilizing the Poincaré-Lindstedt method, we calculated a renormalized expression for the local density of states, providing clear differentiation between the Mott-insulator and Bose-glass phases. Applying a resummation technique, we computed the expression for the disorder ensemble average of the spectral function. Its analysis shows that disorder leads to an increase in the effective mass of both quasi-particle and -hole excitations of the Mott phase. And it yields the emergence of damped states, which exponentially decay during propagation in space and dominate the whole band when disorder becomes comparable to interactions. We argue that such damped-localized states correspond to single-particle excitations of the Bose-glass phase. Our results for the phase boundary compare well against stochastic and local mean-field numerical predictions.
[1] New J. Phys. 23, 083007 (2021) and 25, 063015 (2023)
Keywords: Bose-Hubbard model; disorder; Bose-glass phase; Mott-insulator phase; elementary excitations