Beyond Single Tetrahedron Physics of Breathing Pyrochlore Compound Ba3Yb2Zn5O11

Recently a new class of quantum magnets, the so-called breathing pyrochlore spin systems, have attracted much attention due to their potential to host exotic emergent phenomena. Here, we present magnetometry, heat capacity, thermal conductivity, Muon-spin relaxation, and polarized inelastic neutron scattering measurements performed on high-quality single-crystal samples of breathing pyrochlore compound Ba 3 Yb 2 Zn 5 O 11 . We interpret these results using a simplified toy model and provide a new insight into the low-energy physics of this system beyond the single-tetrahedron physics proposed previously. To probe the high-field magnetic properties of the Ba 3 Yb 2 Zn 5 O 11 crystals, we conducted the magnetic ac-susceptibility and tunnel diode oscillator (TDO) measurements at the DC Field Facility of the National High Magnetic Field Laboratory in Tallahassee, FL. Dilution refrigerator and 3 He systems were used to cover the temperature range from 20 K down to 41 mK. The field dependent measurements up to 18 T were conducted using a superconducting magnet. The low field sweep rate of 0.1-0.3 T/min was used to minimize the magnetocaloric effect. The TDO measurements [8, 9] were carried out on bar-shaped Ba 3 Yb 2 Zn 5 O 11 single crystals of ∼ 2 mm in length and ∼ 1 mm in width and depth. The crystals were placed inside a detection coil, with the [111] direction aligned with the coil axis. The coil and sample within form the inductive component of a LC circuit. The LC circuit, powered by a tunnel diode operating in its negative resistance region, was tuned to resonance at a frequency range between 10 and 50 MHz. The shift in the resonance frequency, which is related to the change in the sample magnetization, was then recorded. With this method, the changes in the magnetic moments can be measured to a very high precision ∼ 10 − 12 emu [9, 10]. The magnetic ac-susceptibility measurements were also conducted to complement the TDO measurements on Ba 3 Yb 2 Zn 5 O 11 single crystals. The samples have a typical dimension of ∼ 4 mm in length and ∼ 0.8 mm in width and depth. A standard two-coil set-up was used. Here, a primary coil was used to apply an oscillating ac-magnetic-field ( ∼ 0.1 Oe - 10 Oe) to the sample, and a secondary coil was used to detect the inducted voltage. The measurements were also repeated for different frequencies: 87.1 Hz, 377.7 Hz, and 1616 Hz. However, We found no dependence on the frequency of the ac-magnetic-field.