SKM 2023 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 23: Kagome Systems
TT 23.9: Talk
Tuesday, March 28, 2023, 11:45–12:00, HSZ 304
Thermodynamics of the spin-half square Kagome lattice antiferromagnet — •Jürgen Schnack1, Oleg Derzhko2, and Johannes Richter3 — 1Fakultät für Physik, Universität Bielefeld, D-33501 Bielefeld, Germany — 2Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 79011 Lviv, Ukraine — 3Institut für Physik, Universität Magdeburg, D-39016 Magdeburg & Max-Planck-Institut für Physik Komplexer Systeme, D-01187 Dresden, Germany
Over the last decade, the interest in the spin-1/2 Heisenberg antiferromagnet (HAF) on the square Kagome lattice has been growing as a model system of quantum magnetism with a quantum paramagnetic ground state, flat-band physics near the saturation field, and quantum scars. Here, we present large-scale numerical investigations of the specific heat, the entropy, as well as the susceptibility by means of the finite-temperature Lanczos method for system sizes of N = 18, ..., 54. We find that the specific heat exhibits a low-temperature shoulder below the major maximum which can be attributed to low-lying singlet excitations filling the singlet-triplet gap, which is significantly larger than the singlet-singlet gap. For the susceptibility the singlet-triplet gap leads to an exponentially activated low-temperature behavior. The maximum of the susceptibility is found at a pretty low temperature T/J = 0.146 (for N = 42). We find a striking similarity of our data with the corresponding ones for the Kagome HAF down to very low temperatures.