Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 41: Quantum-Critical Phenomena (joint session TT/DY)
TT 41.8: Talk
Thursday, March 20, 2025, 11:30–11:45, H31
Continuous order-to-order quantum phase transitions from fixed-point annihilation — •David Moser and Lukas Janssen — TU Dresden, Deutschland
A central concept in the theory of phase transitions beyond the Landau-Ginzburg-Wilson paradigm is fractionalization: the formation of new quasiparticles that interact via emergent gauge fields. This concept has been extensively explored in the context of continuous quantum phase transitions between distinct orders that break different symmetries. We propose a mechanism for continuous order-to-order quantum phase transitions that operates independently of fractionalization. This mechanism is based on the collision and annihilation of two renormalization group fixed points: a quantum critical fixed point and an infrared stable fixed point. The annihilation of these fixed points rearranges the flow topology, eliminating the disordered phase associated with the infrared stable fixed point and promoting a second critical fixed point, unaffected by the collision, to a quantum critical point between distinct orders. We argue that this mechanism is relevant to a broad spectrum of physical systems. In particular, it can manifest in kagome quantum magnets, leading to a continuous quantum phase transition between a gapped chiral spin liquid, which breaks time-reversal symmetry, and a valence bond solid, characterized by broken flavor symmetry. This continuous chiral-spin-liquid-to-valence-bond-solid transition might be observed in herbertsmithite ZnCu3(OH)6Cl2, kapellasite Cu3Zn(OH)6Cl2, or YCu3(OH)6.5Br2.5. Other realizations include Luttinger fermion systems, quantum impurity models, and quantum chromodynamics with supplemental four-fermion interactions.
Keywords: Quantum criticality; Quantum field theory; Strongly correlated systems