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TT: Fachverband Tiefe Temperaturen

TT 27: Focus Session: Tunable Correlations in van der Waals Quantum Materials II (joint session TT/DS/HL)

TT 27.3: Vortrag

Dienstag, 10. März 2026, 10:15–10:30, HSZ/0105

Dirac quantum criticality in twisted double bilayer transition metal dichalcogenides — •Jan Biedermann and Lukas Janssen — Institut für Theoretische Physik and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany

We investigate the phase diagram of twisted double bilayer transition metal dichalcogenides with ABBA stacking as a function of twist angle and pressure. At a filling of 2 holes per moiré unit cell, the noninteracting system hosts a Dirac semimetal with graphene-like low-energy bands. At small twist angles however, interactions dominate the low-temperature physics, stabilizing an antiferromagnetic insulating ground state that is characterized by spin density modulations at the moiré scale. The twist-tuned semimetal-to-antiferromagnet transition is shown to be continuous and belongs to the Gross-Neveu-Heisenberg universality class. We propose that this transition may also be realized by applying uniaxial pressure to a sample, raising the intriguing possibility of experimentally measuring the associated critical exponents for the first time.

Keywords: Strongly Correlated Systems; Quantum-Critical Phenomena; Transition Metal Dichalcogenides; Hartree-Fock; Gross-Neveu Model