Abstract
We present the results of muon-spin spectroscopy (μ+SR) measurements on the molecular spin ladder system (Hpip)2CuBr4(1−x)Cl4x, [Hpip = (C5H12N)]. Using transverse field μ+SR we are able to identify characteristic behaviour in each of the regions of the phase diagram of the x = 0 strong-rung spin ladder system (Hpip)2CuBr4. Comparison of our results to those of the dimer-based molecular magnet Cu(pyz)(gly)(ClO4) shows several common features. We locate the crossovers in partially disordered (Hpip)2CuBr4(1−x)Cl4x (x = 0.05), where a region of behaviour intermediate between quantum disordered and Luttinger liquid-like is identified. Our interpretation of the results incorporates an analysis of the probable muon stopping states in (Hpip)2CuBr4 based on density functional calculations and suggests how the muon plus its local distortion can lead to a local probe unit with good sensitivity to the magnetic state. Using longitudinal field μ+SR we compare the dynamic response of the x = 1 strong-rung material (Hpip)2CuCl4 to that of the strong-leg material (C7H10N)2CuBr4 (known as DIMPY) and demonstrate that our results are in agreement with predictions based on interacting fermionic quasiparticle excitations in these materials.
Highlights
Spin ladders represent a class of low-dimensional quantum magnets that occupy a regime of subtle behaviour which lies between the stark extremes of the one-dimensional chain or two-dimensional plane [1]
For ladders with an even number of legs the ground states are magnetically disordered and show a gap in their excitation spectrum. (They are often described as quantum disordered (QD).) An applied magnetic field B0 acts to close the gap and, at a critical field B0 = Bc, there exists a T = 0 quantum critical point (QCP) above which the excitation spectrum is gapless
Dynamical Regime In order to understand the origin of the transverse field (TF) μ+SR signals reported in section 3 and the longitudinal field (LF) μ+SR signals that will be reported in section 6 we examine the nature of the stopping state of the muon
Summary
Original content from this 7 Eastern Washington University, Department of Chemistry and Biochemistry, Cheney, WA 99004, United States of America work may be used under the terms of the Creative Commons Attribution 3.0 9 Author to whom any correspondence should be addressed. licence. Any further distribution of this work must maintain Keywords: spin ladders, muon spectroscopy, quantum phase transitions, muon site determination, Luttinger liquid parameters, Luttinger attribution to the author(s) and the title of liquids, quantum magnetism the work, journal citation and DOI.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
