arXiv subjects

Daniel G. Nocera

Publications and source records attributed to Daniel G. Nocera.

6 recordsLinked to original sources

arXiv2022

Electronic Thermal Transport Measurement in Low-Dimensional Materials with Graphene Nonlocal Noise Thermometry

In low-dimensional systems, the combination of reduced dimensionality, strong interactions, and topology has led to a growing number of many-body quantum phenomena. Thermal transport, which is sensitive to all energy-carrying degrees of freedom, provides a discriminating probe of emergent excitations in quantum materials and devices. However, thermal transport measurements in low dimensions are dominated by the phonon contribution of the lattice, requiring an experimental approach to isolate the electronic thermal conductance. Here, we show how the measurement of nonlocal voltage fluctuations in a multiterminal device can reveal the electronic heat transported across a mesoscopic bridge made of low-dimensional materials. By using 2-dimensional graphene as a noise thermometer, we demonstrate quantitative electronic thermal conductance measurements of graphene and carbon nanotubes up to 70 K, achieving a precision of ~1% of the thermal conductance quantum at 5 K. Employing linear and nonlinear thermal transport, we observe signatures of long-range interaction-mediated energy transport in 1-dimensional electron systems, in agreement with a theoretical model. Our versatile nonlocal noise thermometry allows new experiments probing energy transport in emergent states of matter and devices in low dimensions.

cond-mat.mes-hall↗

arXiv2014

Thermodynamic Properties of the Quantum Spin Liquid Candidate ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ in High Magnetic Fields

We report measurements of the specific heat and magnetization of single crystal samples of the spin-1/2 kagome compound ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ (herbertsmithite), a promising quantum spin-liquid candidate, in high magnetic fields and at low temperatures. The magnetization was measured up to $μ_{0}H$ = 55 T at $T$ = 0.4 K, showing a saturation of the weakly interacting impurity moments in fields above $\sim10$ T. The specific heat was measured down to $T < 0.4$ K in magnetic fields up to 18 T, revealing $T$-linear and $T$-squared contributions. The $T$-linear contribution is surprisingly large and indicates the presence of gapless excitations in large applied fields. These results further highlight the unusual excitation spectrum of the spin liquid ground state of herbertsmithite.

cond-mat.str-el↗

arXiv2013

Fractionalized excitations in the spin liquid state of a kagomé lattice antiferromagnet

New physics can emerge in magnetic materials where quantum fluctuations are enhanced due to reduced dimensionality and strong frustration. One long sought example is the resonating-valence-bond (RVB) state, where atomic magnetic moments are strongly correlated but do not order or freeze even in the limit of T -> 0. The RVB ground state does not break conventional symmetries, such as lattice translation or spin-rotation. The realization of such a quantum spin liquid in two-dimensions would represent a new state of matter. It is believed that spin liquid physics plays a role in the phenomenon of high-Tc superconductivity, and the topological properties of the spin liquid state may have applications in the field of quantum information. We present neutron scattering measurements of the spin excitations on single crystal samples of the spin-1/2 kagomé lattice antiferromagnet ZnCu3(OD)6Cl2 (also called herbertsmithite). Our observation of a spinon continuum in a two-dimensional magnet is remarkable first. The results serve as a key fingerprint of the quantum spin liquid state in herbertsmithite.

cond-mat.str-el↗

arXiv2011

Synthesis and Characterization of Single Crystal Samples of Spin-$1/2$ Kagome Lattice Antiferromagnets in the Zn-Paratacamite Family Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$

The Zn-paratacamite family, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$ for $x \, \geq$ 0.33, is an ideal system for studying spin-1/2 frustrated magnetism in the form of antiferromagnetic Cu$^{2+}$ kagome planes. Here we report a new synthesis method by which high quality millimeter-sized single crystals of Zn-paratacamite have been produced. These crystals have been characterized by metal analysis, x-ray diffraction, neutron diffraction, and thermodynamic measurements. The $x$ = 1 member of the series displays a magnetic susceptibility that is slightly anisotropic at high temperatures with $χ_{c} \, > \, χ_{ab}$. Neutron and synchrotron x-ray diffraction experiments confirm the quality of these $x$ = 1 single crystals and indicate no obvious structural transition down to temperatures of T=2 K.

cond-mat.str-el↗

arXiv2009

Muon-Spin Spectroscopy of the organometallic spin 1/2 kagome-lattice compound Cu(1,3-benzenedicarboxylate)

Using muon spin resonance we examine the organometallic hybrid compound Cu(1,3-benzenedicarboxylate) [Cu(1,3-bdc)], which has structurally perfect spin 1/2 copper kagome planes separated by pure organic linkers. This compound has antiferromagnetic interactions with Curie-Weiss temperature of -33 K. We found slowing down of spin fluctuations starting at T=1.8 K, and that the state at T->0 is quasi-static with no long-range order and extremely slow spin fluctuations at a rate of 3.6 1/usec. This indicates that Cu(1,3-bdc) behaves as expected from a kagome magnet and could serve as a model kagome compound.

cond-mat.str-el↗

arXiv2006

Ground state and excitation properties of the quantum kagomé system ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ investigated by local probes

We characterize the ground state and excitation spectrum of the $S=1/2$, nominally pure and perfect kagomé system ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ using the following measurements: magnetization, muon spin rotation frequency shift $K$, transverse relaxation time $T_{2}^{\ast}$, and zero field relaxation, and Cl nuclear spin-lattice relaxation $T_{1}$. We found no sign of singlet formation, no long range order or spin freezing, and no sign of spin-Peierls transition even at temperatures as low as 60 mK. The density of states has $E^{1/4}$ energy dependence with a negligible gap to excitation.

cond-mat.str-el↗