Physics (Internal)

Competition between Bose glass and superfluid phases in quantum antiferromagnets

This event is part of the Condensed Matter Theory Seminar Series.

Building on recent NMR experiments [1], we theoretically investigate the high magnetic field regime of the disordered quasi-one-dimensional S=1 antiferromagnetic material DTNX. The interplay between disorder, chemically controlled by Br-doping, interactions, and the external magnetic field, leads to a very rich phase diagram. Beyond the well-known antiferromagnetically ordered regime, analog of a Bose condensate of magnons, we unveil a resurgence of phase coherence at higher field, induced by the doping [2]. Such a ``mini-condensation'' contrasts with previously reported Bose-glass physics in the same regime and should be accessible to future experiments.

In a second part, I will discuss recent findings regarding the one-dimensional superfluid-Bose glass transition at T=0 in S=1/2 XXZ chain [3]. As a function of interaction and disorder strength, we identify a Berezinskii-Kosterlitz-Thouless critical line with two different regimes. At small attraction where critical disorder is weak compared to the bandwidth, the critical Luttinger parameter K takes its universal Giamarchi-Schulz value 3/2. Conversely, a non-universal K>3/2 emerges for stronger attraction where weak-link physics is relevant. In this strong disorder regime, the transition is characterized by self-similar power-law distributed weak links with a continuously varying characteristic exponent.

Refs: [1] A. Orlova et al., Phys. Rev. Lett. 118, 067203 (2017) [2] M. Dupont, S. Capponi, N. Laflorencie, Phys. Rev. Lett. 118, 067204 (2017) [3] E. Doggen, G. Lemarié, S. Capponi, N. Laflorencie, arXiv:1704.02257